the preparation and evaluation of dynamically vulcanized … · elastomer blends prepared by...

Defence Research and Recherche et développement Development Canada pour la défense Canada

The Preparation and Evaluation of

Dynamically Vulcanized Thermoplastic

Elastomeric Materials Based on

Polyamide and Butyl Rubber Polymers

Defence R&D Canada

J.D. Van Dyke, Trinity Western University

M. Gnatowski, Polymer Engineering Company Ltd

Contract Scientific Authority: A.F. Burczyk, DRDC Suffield

The scientific or technical validity of this Contract Report is entirely the responsibility of the contractor and the contents do not necessarily have the approval or endorsement of Defence R&D Canada.

Contract Report

DRDC Suffield CR 2008-210

June 2008

The Preparation and Evaluation of Dynamically Vulcanized Thermoplastic Elastomeric Materials Based on Polyamide and Butyl Rubber Polymers

J.D. Van Dyke Trinity Western University 7600 Glover Road Langley BC V2Y 1Y1 M. Gnatowski Polymer Engineering Company Ltd 110 - 3070 Norland Avenue Burnaby BC V5B 3A6 Contract Number: W7702-06R107/001/EDM Contract Scientific Authority: A.F. Burczyk (403-544-4788) The scientific or technical validity of this Contract Report is entirely the responsibility of the contractor and the contents do not necessarily have the approval or endorsement of Defence R&D Canada.

Contract Report


June 2008

Defence R&D Canada – Suffield

THE PREPARATION AND EVALUATION

OF DYNAMICALLY VULCANIZED

THERMOPLASTIC ELASTOMERIC MATERIALS

BASED ON POLYAMIDE AND BUTYL RUBBER POLYMERS

Contract No: W7702-06R107/001/EDM

Prepared by:

J.D. (Jack) Van Dyke, Ph.D.

Trinity Western University

7600 Glover Road

Langley, BC V2Y 1Y1

Marek Gnatowski, Ph.D.

Polymer Engineering Company Ltd.

#110 – 3070 Norland Ave.

Burnaby, BC V5B 3A6

Prepared for:

Defence Research Establishment Suffield

PO Box 4000

Medicine Hat, Alberta

T1A 8K6

June 3, 2008

2

ACKNOWLEDGEMENTS

THE AUTHORS OF THIS REPORT WOULD LIKE TO THANK DR. A. BURCZYK FOR

EFFECTIVE SUPERVISION AND PARTICIPATION IN THE PROJECT.

WE WOULD ALSO LIKE TO THANK CECILIA STEVENS, PH.D., MATTHEW LEUNG, B.SC.,

DAVE LESEWICK, BEVERLEY START, AND KATE MAO, B.A.SC., OF POLYMER

ENGINEERING COMPANY LTD., AND SEBASTIAN TEMPLE OF TRINITY WESTERN

UNIVERSITY FOR THEIR CONTRIBUTIONS TO THE RESEARCH WORK. APPRECIATION

ALSO GOES TO BRUCE KAYE OF ESQUIMALT DEFENCE RESEARCH DETACHMENT FOR

SAMPLE EVALUATION BY SEM.

.

NOTICE This report was prepared by Polymer Engineering Company Ltd. and Trinity Western University. All the described

tests and technological applications were performed in accordance with our best knowledge and the results represent

our independent judgment.

Furthermore, Polymer Engineering Company Ltd. and Trinity Western University hereby disclaim any and all

warranties, expressed or implied, including the warranties of merchantability and fitness for a particular purpose,

whether arising by law, custom, or conduct with respect to any of the information contained in this report. In no

event shall Polymer Engineering Company Ltd. or Trinity Western University be liable for incidental or

consequential damages because of any information contained in this report. Liability of Polymer Engineering

Company Ltd. and Trinity Western University is limited to fee paid only.

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Abstract

This report presents the results of blending experiments over a two year period on dynamically

vulcanized polyamide / chlorobutyl blends. The objective was to prepare sufficient quantities of

blends in the range of 30 – 40% Nylon by dynamic vulcanization, utilizing the optimum type and

levels of vulcanization agents and process conditions, to allow a comparison of properties

between injection molded, extruded (both machine and transverse direction), and compression

molded specimens. Two curing systems were used – a sulphur and zinc oxide/ZDEDC system.

In addition to mechanical properties the response to solvent attack (swelling index and %

insolubles), resistance to penetration/re-emission of chemical warfare agents, as well as

microscopy on selected samples were tested and compared under different methods of processing.

To ascertain the effect of orientation on mechanical properties an identical die was used for

samples made by injection molding, compression molding, and extrusion. Type M3 specimens

were cut from injection molded bars to allow a direct comparison of properties between molded

and cut M3 specimens. The mechanical results indicate dramatic differences between specimens

produced under various conditions, and there is a strong indication that orientation has a very

large effect on the properties of the blends.

Initial work was also conducted on the modification and reinforcement of both phases of the

blend (Nylon and butyl rubber) with nanoclay. Materials produced were evaluated for

mechanical properties, flow characteristics, and response to solvent attack (swelling index and %

insolubles). Microscopy was performed on selected samples.

TPE materials produced in this project have properties of interest for defence applications,

including HD penetration, and may be used in clothing, boots and face ware applications.

Some of the results of this study contributed to a scientific paper published in the Journal of

Applied Polymer Science, Solvent Resistance and Mechanical Properties in Thermoplastic

Elastomer Blends Prepared by Dynamic Vulcanization, J. Appl. Polym. Sci. 109(3), 1535-

1546, 2008. As well, selected results taken from this study (and other previous studies) were

presented during the RAPRA Technology – Polymers in Defence and Aerospace Applications

conference in Toulouse, France on September 19, 2007. Copies of the paper and presentation are

attached to this report.

Key words

Polyamide 12, chlorobutyl rubber, dynamic vulcanization, swelling index, microstructure, tensile

strength, elongation at break, hardness, resistance to penetration, re-emission.

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TABLE OF CONTENTS page

Introduction/Background 5

Objective of the Project 5

Scope of Work Conducted 6

Experimental Procedures 7

Results of Experiments – Part 1 9

Conclusions – Part 1 11

Results of Experiments – Part 2 12

Conclusions – Part 2 14

LIST OF TABLES

1a. Dynamically Vulcanized Blends by Prep-mixer (Nylon/Rubber)

1b. Dynamically Vulcanized Blends by Twin-extruder (Nylon/Rubber)

2. Summary of Mechanical Properties, Exposure to Solvents, and Penetration/Re-emission Tests

for Nylon Chlorobutyl Blends (nanoclays not present)

3. Chlorobutyl Rubber and Nylon/Chlorobutyl Blends with Nanoclays

LIST OF FIGURES

1. Molding made by injection containing 4 specimens for testing

2. Specimens M-3 injection molded and die cut from injection molded bar taken from the same

specimen set

3. SEM of injection molded M1 and M3 specimens of Nylon / chlorobutyl rubber (40/60) before

and after exposure to external stress. (Inspected surfaces perpendicular to the applied external

stress and flow of material in the mold.)

4. SEM of injection molded M1 and M3 specimens of Nylon / chlorobutyl rubber (40/60) before

and after exposure to external stress. (Inspected surfaces parallel to the applied external stress

and flow of material in the mold.)

5. Comparison of tensile modulus for different sized plastic samples prepared using variety of

processing techniques

6. Comparison of tensile strength at yield for different sized samples of Nylon/CIIR blends

prepared using a variety of processing techniques

7. Comparison of tensile stain at yield for different sized samples of Nylon/CIIR blends prepared

using a variety of processing techniques

8. Comparison of tensile modulus for different sized samples of Nylon/CIIR blends prepared

using variety of processing techniques

9. TEM of blends of Nylon and Nylon/chlorobutyl rubber with nanoclays

APPENDICES

1. “Solvent Resistance and Mechanical Properties in Thermoplastic Elastomer Blends Prepared by

Dynamic Vulcanization”, J. Appl. Polym. Sci. 109(3), 1535-1546, 2008.

2. “Novel Nylon/Halogenated Butyl Rubber Blends In Protection Against Warfare Agents”, RAPRA

Conference, Toulouse, France (18-19 Sept. 2007).

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INTRODUCTION

A. Background to the Project

In previous contracts with Polymer Engineering Co Ltd, W7702-8-R706 and W7702-02R905/001/EDM,

a body of knowledge and expertise was developed to produce thermoplastic material from polyamide

(Nylon) and butyl rubbers using a reactive extrusion technique. These contracts were successful in

producing thermoplastic materials that were resistant to chemical warfare agent penetration and re-

emission while providing moderate physical strength and properties. When prepared by dynamic

vulcanization the morphology of these materials is such that two separate microscopic phases exist, one

consisting of a suitable thermoplastic phase, and the other an elastomeric material. Compatibilization

between Nylon and butyl rubber is achieved by the creation of graft or block polymers that stabilize the

interface between the two polymer phases. Materials made by this process have the properties of heat

moldability and process ability at high processing temperatures while retaining useful elastomeric

performance at working temperatures. Materials and articles produced by this method have provided an

opportunity to integrate blends made from polyamide and butyl rubbers into the CBPlus program within

DRDC Suffield.

Specific conclusions learned in previous contracts for the Nylon-butyl rubber system containing 30-40%

Nylon are that the greatest effect on tensile properties is the presence or absence of halogenation in the

rubber, while percent unsaturation and Mooney viscosity values of the rubber phase have relatively little

effect. Both ultimate strength and percentage elongation decrease in the order of CIIR>BIIR>IIR in

blends containing 40% PA. In Nylon/chlorobutyl rubber blends all samples have improved mechanical

and penetration properties when curatives are present, although mechanical properties reach a plateau at

relatively low quantities of vulcanization agent. Extruded samples show lower values of re-emission than

for comparable samples produced by injection molding.

The morphology of Nylon/butyl rubber blends has been investigated by measurement of swelling index of

the rubber phase. Statically produced blends of similar composition show significantly larger swelling

indices for the rubber phase than for samples of similar composition prepared by dynamic vulcanization.

This is likely due to a large “caging effect” on the rubber phase in dynamically vulcanized materials.

When swelling index of the rubber phase is correlated with composition of Nylon in the blends, it is

observed that the plot undergoes a unique change in slope at a composition of approximately 25% Nylon.

By reference to scanning electron microscopy, it is suspected that this composition roughly corresponds

to a Nylon/rubber ratio where the continuous phase in the system becomes dominated by the uncured

thermoplastic phase. This composition also seems to be the approximate point where not only the

elongation at break values reach a minimum, but also where values of re-emission of warfare agents

undergo a change in slope versus composition.

B. Objective of the Project

The objective of the proposed blending program was to optimize and enhance the physical and chemical

properties of the Nylon/chlorobutyl TPE system. Mechanical properties, effects of solvent on the blends,

and microscopy were to be compared for specimens prepared by injection molding, extrusion (machine

and transverse directions), and compression molding. An identical die (Type M3) for all three processing

methods was available to facilitate mechanical property comparisons. This included a comparison

between identical tensile specimens on molded M3 specimens versus ones cut from impact bars.

Mechanical properties were to be correlated to swelling index and microscopy at different compositions

and different methods of processing to establish relationships between morphology and composition. A

further objective was to conduct initial work on the modification and reinforcement of both phases of the

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blend (Nylon and butyl rubber) with nanoclay, to potentially improve HD penetration and re-emission

properties of blends.

SCOPE OF WORK CONDUCTED

The detailed scope of experimentation conducted as part of this study was as follows:

1. Nylon/chlorobutyl rubber blends in the range of 30 – 40% Nylon were prepared by dynamic

vulcanization utilizing the optimum type and levels of vulcanization agents and process conditions

established in previous investigations. The Brabender Plasticorder laboratory extrusion apparatus, a small

scale high shear internal mixing system, was used for all blends. Further optimization on the cure system

and processing conditions was also undertaken. Sufficient quantities were produced through multiple

blends to allow a comparison of properties between injection molded, extruded (both machine and

transverse direction), and compression molded specimens, as well as standardized HD agent penetration

and remission tests at DRDC Suffield. The effect of orientation on mechanical properties for these

specimens was determined. SEM evaluation of blends was conducted on selected samples prepared by

different processing methods in order to establish correlations to morphology. This work also served to

qualify the prospective material with the intention of incorporating it into new decontamination and

protective equipment designs.

An initial evaluation of the mechanical properties of Nylon/butyl rubber blend specimens made by

injection molding, compression molding, and extrusion showed significant differences in tensile

properties when tested according to the recommended ASTM procedures. As a result the mechanical

testing was extended using an identical die (ASTM D-638M type M3) for all three processing methods.

To facilitate a valid comparison, additional specimens were cut from the injection molded bars. Thus

comparisons could be gained between M1 and M3 specimens made under the same molding conditions,

as well as comparisons of these results to M3 specimens that were cut from the impact bar. (see figure 2).

This provided a direct comparison of the resin flow effect on mechanical properties, because the injection

molded and die cut specimens were taken from the same material with identical thermal and shear history.

2. Additional investigation using swelling index and microscopy was undertaken on samples of

Nylon/chlorobutyl rubber in the range of 15 – 50% Nylon to confirm a number of results on the

relationship of composition to morphology of blends and the effect this may have on particular properties

such as elongation, tensile strength, hardness, and solvent resistance of blends, for the major study to be

published in the Journal of Applied Polymer Science. This article is complete and a copy is attached as

Appendix I to this report. (see “Solvent Resistance and Mechanical Properties in Thermoplastic

Elastomer Blends Prepared by Dynamic Vulcanization” by J. Van Dyke, M. Gnatowski and A. Burczek,

J. Appl. Polym. Sci. 109(3), 1535-1546, 2008) Comparisons of swelling index and insolubles were also

undertaken on different methods of processing.

3. Initial work was conducted on modification and reinforcement of both phases of the blend (Nylon and

butyl rubber) with nanoclay. This reinforcement should improve resistance of the blend to warfare agent

penetration, and reduce re-emission. A selection of nanoclay components was tested. Three to five

selected blends containing nanocomposite were made and molded initially. Injection molded and thick

extruded (above 6 mils) and compression samples were evaluated for mechanical properties, flow

characteristics, and response to solvent attack (swelling index and % insolubles). Microscopy, including

TEM, was performed on selected samples.

4. It was expected that a research presentation of this body of work would be made at an appropriate

polymer conference in 2007 to be determined during the course of the contract. The forum chosen was

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the International Conference on Polymers in Defence and Aerospace 2007, Toulouse, France (18-19 Sept.

2007) organized by RAPRA. A copy of the presentation is attached as Appendix II.

5. Previous work has shown that the TPE’s produced can be welded and seam sealed. An investigation

was undertaken on the welding of Nylon/chlorobutyl TPE’s onto pure Nylon fabric. CW agent

penetration of such welded seam articles will be conducted at DRDC Suffield using HD in standardized

agent penetration tests.

EXPERIMENTAL PROCEDURES

1. Blend Preparation

Because of the detailed descriptions of sample preparation and test procedures given in detail in the

scientific paper attached to this report (see Appendix I), this section will give brief overall descriptions,

rather than full detail.

a) Nylon/Chlorobutyl Blends Without Nanoclays

All blends were prepared in batches of approximately 235 grams each using a 258 cc capacity 5 HP

Plasticorder EPL-V5502 equipped with Prep Mixer type R.E.E.6 and type 808-2504/PSI/DTI Rheometer

and temperature control (Brabender Instruments Inc., Hackensack, NJ). For all dynamically-vulcanized

blends, the plastic resin was first added at 30 rpm mixing speed to the Brabender Mixer at a target

temperature of 190ºC, and allowed to melt for 2 minutes. The rubber was then added along with stearic

acid, metal oxides, and wax, and the mixing speed was increased to 65 rpm. Mixing was continued for an

additional 6 minutes. After a total mixing time of 8 minutes, the active curing agent was added and

allowed to mix for 4.5 minutes (mixing time of 12.5 minutes). The blend was removed from the mixer

after a total of 14 minutes and cooled.

In the first step of the research four Nylon 12/chlorobutyl rubber blends were prepared with Nylon/rubber

ratios of 30/70 and 40/60. Two types of curing agents were used – sulphur, and zinc oxide/ZDEDC. The

formulations are shown in Table 1a. A total of 10 batches were made for each formulation, then ground

and mixed together to assure identical materials for sample preparation and testing.

b) General Blend Procedure for Rubber Without Nanoclay

Chlorobutyl rubber was masticated at 25 rpm and a set temperature of 50ºC for 3 minutes, after which

stearic acid and zinc oxide were added, and mixing continued for an additional 2 minutes. ZDEDC was

then added, and mixing was complete after an additional 5 minutes. The total mixing time was 10

minutes. If the blend was sulphur-based, stearic acid, zinc oxide, and antioxidant were added after 3

minutes, MBTS and TMTD after an additional 2 minutes, and sulphur after a further 3 minutes. The total

mixing time was also 10 minutes. The curing levels (based on rubber) were identical to those used in the

Nylon/chlorobutyl blend experiments. After mixing was complete, the compound was compression

molded at 160ºC for 30 minutes.

c) Experiments to Prepare Nylon/Chlorobutyl Blends for Extrusion

Extrusion blending was used to prepare 40/60 and 30/70 sulphur-cured Nylon/chlorobutyl blends. Prior

to extrusion Nylon12 was ground into powder and dried. Then the rubber was pre-weighed, frozen with

dry ice, and ground with 4mm sieve. All other components were pre-weighed and added to the frozen

rubber. The contents were shaken well and spread out on the bench to thaw and dry, and subsequently

poured into a twin feeder and extruded. The mixtures were passed 4 times through the extruder with

samples taken for mechanical testing after each pass. After the first pass the twin feeder was no longer

required. The formulations of the blends are shown in Table 1b.

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d) Addition of Nanoclays to Chlorobutyl Rubber and Nylon/Chlorobutyl Rubber Blends

In the second phase of the research nanoclays were blended with chlorobutyl rubber in the presence and

absence of a maleinated coupling agent (5% Fusabond MZ203D). Nanoclays were mixed into 40/60

Nylon/chlorobutyl blends in two ways, first through a pre-blend with chlorobutyl rubber, and second

through a pre-blend with Nylon 12. Using pre-blends the formulations were adjusted to ensure that the

volume ratio in the final mixture was correct for each blend. The formulations are listed in Table 3.

Further details on specifics of the blends are listed along with the results in Part 2 (see page 12ff).

2. Testing and Characterization

a) Molding and Sample Preparation – Compression molded 5" x 5" sheets, approximately 2 mm thick,

were prepared in a press at a temperature of 205oC for 4 minutes. Specimens were cut from the sheets

using a die according to ASTM D-412. Injection molded samples (4 specimens each – see figure 1) were

made using an Arburg Allrounder K221 injection molding machine. All zone temperatures were 205oC

with a nozzle temperature of 208oC and molding cycle time of approximately 45 seconds. Extrusion of

the blends in the form of sheets was done using a Brabender ¾” single screw extruder with 100mm wide

ribbon die. The extruder speed was set at 80 rpm with zone temperatures of 205oC each and a die

temperature of 200oC. Specimens for testing were cut in the machine direction using the die

recommended by ASTM D-412, or in the form of strips as per ASTM D-882. Specimen size and method

of preparation was done based on experience from previously conducted experiments.

b) Mechanical properties – Mechanical properties were tested on specimens prepared by compression

molding, injection molding, and extrusion (see Table 2). A computerized Instron 4400 Universal Testing

Machine equipped with a video extensometer (Bluehill software) was used to determine stress/strain

characteristics on each sample according to the American Society for Testing and Materials procedures

D-412, D-638, and D-882. Hardness values (Shore A and D) were determined by ASTM D-2224 using a

PTC Type A Durometer Gauge Model 306L or Type D Durometer Gauge Model 307L (PTC

Instruments).

c) Swelling index and percentage insolubles – Samples of blends, and molded or extruded specimens,

were sent to Trinity Western University for analysis of swelling index and % insolubles of individual

blends in hexane solvent. Swelling index and percentage insolubles were determined on molded or

pressed samples, ~1 cm square and 1.5 mm thick, that were immersed in hexane for 4 days to obtain

equilibrium. The swelling index of a blend sample was determined by comparison of the weight of the

swollen sample to its weight after drying to constant weight. The % insolubles of the sample in the

solvent were determined by comparison of the dried sample to its original weight. In addition to

individual samples these tests were also undertaken on the composite sample for each type of blend and

on samples produced by injection molding, compression molding and extrusion. Swelling index and %

insolubles data are included in Table 2.

d) Microscopy – Scanning electron microscopy (SEM) was conducted using a variable pressure LEO

1455VP microscope (Meridian Scientific Services, Stittsville, ON, Canada). Specimens were prepared by

cutting with a sharp blade or by fracture after cooling in liquid nitrogen. All samples were stained with

osmium tetroxide, but staining was particularly effective in samples containing nitrile rubber. The blends

were mounted on aluminum stubs with carbon paint, and examined without coating at low pressure using

a Robinson Backscatter Detector. Transmission electron microscopy (TEM) was conducted on extruded

thin films which were cast into epoxy and microtomed.

e) Penetration and re-emission tests – conducted according to standard tests at DRDC Suffield using

molded specimens provided by Polymer Engineering Co. Ltd., and the data are included in Tables 2 and

3.

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RESULTS OF EXPERIMENTS

Part 1 – Mechanical Properties, Solvent Exposure, and HD Penetration/Re-

emission of Nylon/Chlorobutyl Blends (No addition of Nanoclays)

General observations on Nylon/Chlorobutyl Blends are as follows. Refer to Table 2:

a) Effect of Sample Type in Injection Molded Samples

Results:

1. In general tensile strength at break is much higher for M3 specimens than M1 specimens. This is

particularly true for dynamically vulcanized Nylon/chlorobutyl samples prepared by sulphur cure.

2. Tensile strength values for M3 specimens prepared by cutting from the impact bars are much less

than for injection molded M3 samples. The values of cut M3 specimens approach those for M1

specimens prepared by injection molding, and are usually within 1 MPa.

3. Although tensile strength is strongly affected by sample size (M3 vs. M1), the elongation at break

(%) is not significantly different between samples. As is the case for tensile strength, it would appear

that elongation at break for an M3 sample cut from an impact bar is a reasonably good measure of the

percent elongation by the M1 test.

b). Effect of Orientation on Tensile Strength and Elongation

General relationship between orientation and tensile strength at break in samples: Increasing orientation

causes tensile strength to increase.

Comparison of tensile specimens – symbols used:

a) compression molded M3 specimen (C)

b) M1 injection molded specimen (I-M1)

c) injection molded impact bar with cut M3 specimen (I-M3 (cut))

d) injection molded M3 specimen (I-M3)

e) extruded M3 specimen transverse direction (E-T)

f) extruded M3 specimen, machine direction (E-M)

4. Results – Effect of sample preparation method on tensile strength:

a) 30/70 Nylon/CIIR – DV - both sulphur and ZDEDC cure:

C < E-T < I-M3 (cut) < I-M1 < E-M < I-M3

b) 40/60 Nylon/CIIR – DV - sulphur cure:

C < I-M1 < E-T < I-M3 (cut) < E-M < I-M3

c) 40/60 Nylon/CIIR – DV - ZDEDC cure:

C < I-M1 < E-M < I-M3 (cut) < E-T < I-M3

Observations: There are slight differences between the 40/60 and 30/70 samples. As well, there are

slight differences between sulphur cured and ZDEDC cured samples. Compression molding always

provides the lowest tensile strength value, and injection molded M3 specimens always the highest.

Extruded samples in the machine direction are higher than in the transverse direction. M3

specimens cut from injection molded bars are a relatively close approximation of M1 molded

specimens.

5. Results – Effect of sample preparation method on elongation at break:

Sample type and orientation have a much different effect on elongation at break than tensile strength.

a) 30/70 Nylon/CIIR – DV - sulphur cured:

C < I-M3 (cut) < I-M3 < I-M1 < E-T < E-M (note: in this series the values of injection

molded samples are approximately equal.)

b) 30/70 Nylon/CIIR – DV - ZDEDC cured:

C < I-M1 < I-M3 < I-M3 (cut) < E-T < E-M

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c) 40/60 Nylon/CIIR – DV - sulphur cured:

C < I-M1 < I-M3 < I-M3 (cut) < E-T < E-M (note: in this series the values of injection

molded samples are relatively close in value)

d) 40/60 Nylon/CIIR – DV - ZDEDC cured:

C < I-M1 < E-M < E-T < I-M3 (cut) < I-M3 (note: in this series the values of percent

elongation in extrusion samples are not

the highest values, in contrast to tests for

the other three sets.)

c). Other Observations on Mechanical Properties

Results:

6. Comparison of sulphur to ZDEDC cure: Higher tensile strength and percent elongation at break for

both 30/70 and 40/60 samples are obtained by sulphur cure. In the 40/60 – sulphur cured sample this is

seen for both injection molded and extrusion prepared samples. An injection molded specimen of this

composition (I-M3 (cut)) has a tensile strength of 13.3 MPa and percent elongation at break of 280%,

while an extrusion prepared sample of this type has approximately 13 MPa and 300%, respectively.

7. In two of the groups of samples it is observed that specimens with a high value of modulus (MPa)

also have low percent elongation at break, and vice versa. Example for 40/60 – ZDEDC-cured samples:

compression molded samples - elongation at break low, modulus high; injection molded M3 (cut)

samples – elongation at break high, modulus low. A lower value of modulus often indicates a more

rubbery material. Thus sample preparation method has a large effect on mechanical properties.

8. In all blend combinations the hardness value (Shore D or Shore A) is higher for the injection molded

samples over compression molded samples. This is likely due to the higher heat history in injection

molded samples, creating a more highly cured rubber phase.

d). Effect of Curing

Results:

9. Using swelling index of the rubber phase as an indicator of the extent of curing in the rubber phase, it

is observed for sulphur-cured samples that curing increases in the order of compression molded <

extrusion < injection molded. In ZDEDC-cured samples the order is compression molded < injection

molded < extrusion.

10. ZDEDC-cured samples are not as highly crosslinked as sulphur-cured samples. Since lower curing

of the rubber phase seems to parallel lower values of tensile strength and percent elongation at break,

there is a possibility that higher mechanical property values might be obtained in ZDEDC-cured

samples if higher levels of curing agent are used.

11. Completeness of cure is best determined by the percent insolubility values in hexane. For all

sulphur cured samples the percent insolubility is very high (98% or greater); however, in ZDEDC-cured

samples the percent insolubility for 30/70 samples is approximately 80%, and for 40/60 samples it is

approximately 90%. An increased value of percent insolubility again may parallel higher values of

tensile strength and percent elongation at break.

e). Effect of Blending by Extrusion

Results:

12. In sulphur-cured samples of both 30/70 and 40/60, trials were conducted to determine if the blends

could be made by extrusion. The ingredients were dry-mixed and passed through an extrusion cycle

four times. Trials were conducted with Nylon L16 and L25, with the L25 material having the higher

melt viscosity. After each extrusion cycle a portion of the blend was tested for mechanical properties,

% insolubility, and swelling index.

a) In 30/70 samples using Nylon L16 both tensile strength and % elongation decreased with

successive extrusion cycles, losing about 50% of their values by the fourth cycle.

b) In 40/60 samples with Nylon L16 the tensile strength reduced by about 1 MPa over successive

cycles and % elongation reduced to about 60% of its value with the first cycle. The swelling index and

% insolubility values indicate that the rubber phase was not as extensively crosslinked as when the

11

sample was prepared by the batch process. Successive extrusion cycles did not have a measurable

effect on the swelling index of the rubber phase.

c) Nylon L25 was attempted in hopes that a higher viscosity Nylon phase would improve the

mixing of the plastic phase with the rubber phase. Using L25 the tensile strength values do not

decrease as much over the four cycles; however, elongation at break values are very low in comparison

to those for the L16 blends. As well, the swelling index values increase and % insolubility values

decrease with successive cycle times, suggesting that the rubber phase is slowly breaking down as

cycles increase.

f). Effect of Sample Preparation Method on HD-Penetration and Re-emission

Results:

13. Samples with a higher % Nylon generally had lower penetration to warfare agents. In addition,

sulfur-cured samples have higher penetration but lower re-emission values than ZDEDC-cured samples.

In general, the extruded samples have both higher penetration and re-emission values.

14. Repeated extrusion cycles on mixtures of Nylon/CIIR cause an increase in re-emission values for

30/70 blends. There is no noticeable trend for 40/60 blends.

SEM pictures – refer to Figures 3 and 4

Results:

Figures 3 and 4 show several SEM micrographs of a sulphur-cured 40/60 Nylon/chlorobutyl blend (#

060717-1). Injection molded M1 and M3 specimens are shown before and after exposure to stress. It is

evident that stress causes substantial deformation of the discrete phase in the blends, whether observed

parallel to the applied external stress or perpendicular to it. As well, the orientation of the rubber particles

is somewhat greater for stressed M3 specimens than similar M1 specimens, which may be derived from a

higher resin flow effect in the smaller M3 specimen during molding.

Conclusions on Part 1 (Mechanical Properties, Solvent Exposure, and HD Penetration/Re-emission

of Nylon/Chlorobutyl Blends (No addition of Nanoclays)

1. The best tensile strength values are obtained for injection molded and extruded specimens. Lower

tensile strength values are associated with compression molding.

2. Properties such as tensile strength, elongation at break, and modulus of elasticity vary significantly

with differently shaped specimens, even when all specimens are molded at the same time. The flow

history of the material in the mold cavity seems to be a major factor affecting the properties.

3. For small dumbell samples the values of tensile strength are much larger than for larger specimens (see

M3 results vs. M1 results). The results of tensile tests are reasonably close between the M1 molded

specimens and M3 specimens cut from impact bars. With respect to elongation at break, the

differences between M1 and M3 specimens are much less than for tensile strength. However, M3

specimens cut from an impact bar are a reasonable approximation to the M1 values.

4. When a molten mixture flows rapidly into a small space and cools rapidly, freezing it into an oriented

state, (e.g. small dumbell samples), much higher values of tensile strength are produced. If this data

were to be published, it would be important to compare the results obtained on these mixtures to those

undertaken on pure Nylon samples. (see conclusions in Part 2) In addition, it would be helpful to

determine the flow pattern in a mold in order to understand the morphology that is built into the

different samples. An understanding of flow and flow history is important in knowing how to

produce these blends in future commercial application.

5. Orientation effects seem to follow the expected course, with compression molded samples less

oriented than extrusion and injection molded samples. Some differences are evident between sulfur

cured and ZDEDC cured samples in terms of orientation effects.

12

6. For extruded samples there are some clear differences between those cut in the machine vs. transverse

directions. Samples in the machine direction display both higher tensile strength and percent

elongation.

7. Sulfur cured samples have the highest values for tensile strength and percent elongation. This is also

accompanied by higher values of cure in the rubber phase.

8. The sample with the best combination of properties is the 40 Nylon/60 CIIR sample cured with sulfur.

Tensile strength in excess of 13 MPa and elongation of 300% can be obtained. However the hardness

values for the 40/60 blends are higher than for 30/70 blends.

9. In both 30 Nylon/70 CIIR and 40 Nylon/60 CIIR blends the mechanical properties were not improved

by extrusion mixing. A change to Nylon L25 in place of L16 – to provide a higher viscosity Nylon to

match the rubber phase – did not change this result.

10. Because the 30/70 and 40/60 blends do not have improved results by extrusion mixing, we may be

restricted to batch mixing for these samples. This is in contrast to the results on the mixing of 50/50

blends, where extrusion mixing produced superior results over batch. Since Nylon acts as a lubricant

in mixtures of this nature, lower quantities of Nylon may result in too high a shear imposed on the

rubber portion of the sample.

11. In 40/60 samples containing Nylon L25 there was a decrease in percent insolublilty with successive

extrusion cycles. The reason for this may be that the rubber extracted into the solvent (hexane) may

show grafting, or there could be an oxidation in the rubber phase taking place. One idea for the future

is to repeat these extractions with CHCl3, as this solvent is a slightly better solvent for Nylon, and if

graft polymer is observable it may be easier seen in the CHCl3 solvent.

12. HD penetration and re-emission tests indicate that all samples pass the specifications. However,

repeated extrusion on samples high in rubber content may cause a loss in penetration and re-emission

resistance. As well, injection molded samples tend to have lower values of both penetration and re-

emission than extrusion-prepared samples.

13. SEM Microscopy reveals that stress applied to molded Nylon/chlorobutyl blends produces a clearly

observable deformation in the rubber particles. Deformation and recovery in the discrete phase

during stress and release is believed to increase both tensile strength and elongation at break for these

blends. (see VanDyke et. al. “Solvent Resistance and Mechanical Properties in Thermoplastic

Elastomer Blends Prepared by Dynamic Vulcanization” J. Appl. Polym. Sci. 109(3), 1535-1546, 2008

– attached as Appendix I)

Part 2 – Mechanical Properties, Solvent Exposure, and HD Penetration/Re-

emission for Experiments of Nylon and Chlorobutyl With Nanoclays

General observations on Chlorobutyl Rubber Formulations with and without nanoclays, and

Nylon/Chlorobutyl Blends with and without nanoclays are as follows. Refer to Table 3. A maleinated

coupling agent (Fusabond) was sometimes added in addition to nanoclays to promote compatibility.

a) Chlorobutyl Blends with Nanoclay – Pressed Sheets

All of the blends in this series contain pure CIIR and sometimes Fusabond and sometimes Nanoclay.

Typically these were mixed by first doing a pre-blend (070706-1, 2) of CIIR with Fusabond at 170°C

for 6 minutes. This allowed Fusabond to be prepared as a concentrate in CIIR. This concentrate was

added to additional CIIR, and the mixture was blended in the prep mixer (R.E.E. 6) at low temperature.

The mixture was cured in the press at high temperature. The results are:

1. Re-emission values – When Fusabond is present, the addition of nanoclay reduces the re-emission

result. However, when no Fusabond is present, the addition of nanoclay increases the re-emission

value. Overall, when Fusabond is present, the values of re-emission are much lower than when it

is absent, with or without nanoclays. It is postulated that Fusabond helps reduce “space” between the

13

Zn particles and the rubber network, thus reducing capillary action to move HD agents through the

rubber matrix. 2. Mechanical Properties (general) – whether Fusabond is present or absent, the addition of nanoclay to

a rubber formulation increases the tensile strength at break, percent elongation, modulus, hardness (both

Shore A and Shore D). Nanoclays appear to harden the rubber formulation. This is particularly evident

in sulphur-cured pressed sheets.

3. Solvent Exposure – in ZDEDC cured formulations the addition of nanoclays causes an increase in

swelling index, indicating a reduced level of cure. This effect is not present in sulphur cured

formulations. As well, the values of swelling index are higher in pure rubber samples when no

Fusabond is present. This fact appears to correlate with increased re-emission values in the absence of

Fusabond.

b) Nylon/Chlorobutyl Blends with Coupling Agent and Nanoclay – nanoclay in rubber phase

To prepare this series (e.g. 070725-2) a pre-blend (070723-5,6,7,8) containing CIIR, Fusabond and

Nanoclay (I 44P) was pre-mixed at 170°C. To this was added pure Nylon and the dynamic

vulcanization ingredients, and the blend prepared in the prep mixer (R.E.E. 6). (In the case of 070731-5

the pre-blend was 070730-1,2,3 containing CIIR plus clay ) The results are:

1. Mechanical Properties – The addition of nanoclay to the rubber phase in these samples decreases the

tensile strength at break, the percent elongation, and the modulus. Hardness values are increased.

2. Mechanical Properties Comparison – In sulphur-cured and ZDEDC-cured blends containing no

nanoclays, the values of tensile strength and percent elongation are reasonably similar with Fusabond

present or absent.

3. Re-emission values – The values of re-emission increase with addition of nanoclay, indicating that

nanoclay has no beneficial effect upon the barrier properties when added in this manner to the rubber

phase only. The addition of Fusabond also increases the re-emission values over standard 40/60

Nylon/chlorobutyl rubber blends. Overall, for these experiments with nanoclay added to the rubber

phase the re-emission results are very high, and substantially higher than those obtained with Nylon and

CIIR alone.

c) Nylon/Chlorobutyl Blends with Coupling Agent and Nanoclay – nanoclay in plastic phase

In these samples Nanoclay I 30E was first mixed with Nylon at the Brabender company using a co-

rotating extruder. Then this pre-blend was mixed at PEC with rubber and dynamic vulcanization

components in the prep mixer (R.E.E. 6). No maleinated coupling agent was added. The mixture was

then injection molded and tested. Results are

1. Mechanical Properties – Both tensile strength at break and elongation at break are affected

moderately by the addition of nanoclay.

2. Penetration and Re-emission values – Both of these properties are improved by the addition of

nanoclays. As well, it is very clear that when nanoclays are added to the plastic phase, as is the case in

this set, the penetration and re-emission values are much more favourable than when added to the

rubber phase alone (set (b) above).

d) Nylon 12 (L16) Films Containing Nanoclays

A Nylon sample was pre-mixed with Nanoclay I 30E at C.W. Brabender, using a co-rotating extruder

(071115-7). This sample was compared to one that did not have nanoclay added. Both samples were

extruded into film at the Brabender plant. The results are:

1. Mechanical Properties – Addition of nanoclay to Nylon reduces both tensile at break and elongation

at break.

2. Penetration and Re-emission values – Penetration values are not affected by nanoclay, but re-

emission values are less.

14

e) Comparison of tensile properties by different test methods for samples of pure Nylon and Nylon/CIIR

(see Figures 5,6,7, and 8)

1. For pure Nylon the injection molded tensile properties (yield strength) show very little difference

between M3 and M1 specimens. (see Figure 5)

2. For 30/70 and 40/60 Nylon/CIIR blends cured either with sulphur or ZDEDC, there are large

differences between injected molded M3 tensile specimens and injected molded M1 tensile specimens.

It appears that the effect of shear is very great on blends containing rubber and Nylon. However, when

M3 specimens are cut from impact bars the tensile result is very similar to an injection molded M1

specimen. The orientation factor in cut M3 specimens is substantially less than for M3 specimens that

are directly injection molded. (see Figure 6)

3. As a whole it appears that yield strain (%) is approximately similar for the various test methods,

injection molded M1 and M3 specimens, M3 specimens cut from impact bars, and M3 specimens cut

from compression molded sheet.

4. Values of modulus for Nylon/chlorobutyl rubber mixtures are relatively similar for injection molded

M1 and M3 specimens. Values are generally lower for M3 specimens cut from impact bars and

compression molded sheet.

f) TEM pictures of a Nylon/Nanoclay Blend and a Nylon/CIIR/Nanoclay Blend – refer to Figure 9

Figure 9 shows TEM micrographs of a Nylon/nanoclay blend and a 50/50 Nylon/chlorobutyl/nanoclay

blend. In both cases the Nylon phase contains 10% nanoclay. The micrographs in Figure 9 were

obtained as part of another project using similar materials, and are attached to this report as

representative of these types of blends. In the Nylon/nanoclay blend the nanoclay particles are

exfoliated and oriented, as is desirable to provide improved barrier properties. In the

Nylon/CIIR/nanoclay blend the elongated gray particles most likely correspond to the nanoclay

component added to the blend, and the spherical particles represent the mineral components of the

blend added to the rubber phase for vulcanization purposes. No evidence of exfoliation and orientation

of nanoclay particles in the Nylon/CIIR/nanoclay blends can be seen, which is an indication that the

addition of nanoclays to these blends is not optimized using the processing techniques employed to this

point. As a result, further TEM micrographs were not taken of blends with 30 and 40% Nylon.

Conclusions on Part 2 Mechanical Properties, Solvent Exposure, and HD Penetration/Re-emission

for Experiments of Nylon and Chlorobutyl With Nanoclays

1. On pressed and cured chlorobutyl rubber sheets the main goal of improved re-emission results with

addition of nanoclay particles was not achieved. However, when Fusabond is added to these

formulations, the addition of nanoclays reduces the re-emission result.

2. On pressed and cured chlorobutyl rubber sheets the addition of nanoclay causes a substantial increase

in tensile strength at break and modulus.

3. The addition of nanoclay to the rubber phase in Nylon/chlorobutyl rubber blends decreases the tensile

strength at break, the percent elongation, and the modulus. As well, the values of re-emission

increase, indicating that nanoclay has no beneficial effect upon the barrier properties when added in

this manner to the rubber phase only.

4. In Nylon/chlorobutyl rubber blends with nanoclays added to the plastic phase the penetration and re-

emission values of the blends are the lowest of all samples of blends. This method provides excellent

barrier materials. The tensile strength and elongation at break are affected only moderately by the

addition of nanoclay.

5. For injection molded samples of Nylon there is very little effect of specimen type (M1 vs. M3) on

tensile properties. However, in blends of Nylon/chlorobutyl rubber the differences are substantial,

indicating that orientation introduced in the molding process can have a very large effect on the

properties of these blends. For comparison of tensile properties an M3 specimen cut from an impact

bar is a relatively close approximation to the molded M1 bar.

15

6. Exfoliation and alignment of nanoclay particles is successful in Nylon/nanoclay blends. Less success

has been obtained with nanoclays added to Nylon/CIIR blends.

Other Tests Run:

A number of Nylon/chlorobutyl TPE’s were prepared and welded onto pure Nylon fabric. These samples

were sent to DRDC Suffield for standardized HD agent penetration tests.

16

Figure 1. Molding made by injection containing 4 specimens for testing

Figure 2. Specimens M-3 injection molded and die cut from injection molded bar taken from the same specimen set

M-1

M-3

Injection

molded Die cut

17

Figure 3. SEM of Injection molded M1 and M3 specimens of nylon / chlorobutyl rubber (40/60) before and after exposure to external stress. (Inspected surfaces perpendicular to the applied external stress and flow of material in the mold.)

a) M1-unstressed b) M1-stressed c) M3-unstressed d) M3-stressed

a) b)

c) d)

18

Figure 4. SEM of Injection molded M1 and M3 specimens of nylon / chlorobutyl rubber (40/60) before and after exposure to external stress. (Inspected surfaces parallel to the applied external stress and flow of material in the mold.)

a) M1-unstressed b) M1-stressed c) M3-unstressed d) M3-stressed

a) b)

c) d)

23

Figure 9: TEM of Blends of Nylon and Nylon/chlorobutyl rubber with nanoclays a) Nylon with 10% nanoclay added b) 50/50 Nylon/chlorobutyl rubber blend with 10% nanoclay added to the nylon phase

24

Table 1a - Dynamically vulcanized blends by prep-mixer

(Nylon/Rubber) Apr.18/07

Components Pre-Blend (Blend ID)

(060717-1 - 060719-3) (060724-1 - 060727-1) 060802-1 060809-1 - 060814-1

Nylon12 (L16) - 1) 40.0phr 1) 30.0phr 1)

40.0phr 1) 13.20phr

Nylon12 (L25) - - - - -

ChloroButyl1068 - 2) 60.0phr 2) 70.0phr 2)

60.0phr 2) 56.04phr

Naugard445 - 4) 0.60phr 4) 0.60phr 4)

0.60phr -

Stearic Acid 150 - 3) 1.44phr 3) 1.44phr 3)

1.44phr 3) 1.44phr

Paricin Wax 285 - 5) 0.55phr 5) 0.55phr 5)

0.55phr 4) 0.55phr

ZDEDC - - - - -

060808-1 - - - 5) 5.28phr

Zinc Oxide 103 - 6) 3.60phr 6) 3.60phr 6)

3.60phr -

Zinc Oxide 172 - - - - -

060803-1 - - - 6) 33.50phr

Sulphur - 7) 1.44phr 7) 1.68phr 7)

1.44phr -

MBTS - 8) 0.54phr 8) 0.54phr 8)

0.54phr -

TMTD - 9) 1.08phr 9) 1.08phr 9)

1.08phr -

Components Pre-Blend (Blend ID)

060814-2 - 060817-1 070604-1 - 070604-2

Nylon12 (L16) - 1) 3.20phr -

Nylon12 (L25) - - 1) 40.0phr

ChloroButyl1068 - 2) 65.38phr 2) 60.0phr

Naugard445 - - 4) 0.60phr

Stearic Acid 150 - 3) 1.44phr 3) 1.44phr

Paricin Wax 285 - 4) 0.55phr 5) 0.55phr

ZDEDC - - -

060808-1 5) 6.16phr -

Zinc Oxide 103 - - 6) 3.60phr

Zinc Oxide 172 - - -

060803-1 6) 33.50phr -

Sulphur - - 7) 1.44phr

MBTS - - 8) 0.54phr

TMTD - - 9) 1.08phr

060808-1 - 75-CIIR1068 / 25-ZDEDC uncured

060803-1 - 80-PA12(L16) / 20-ZnO172 pelletized by twin extrusion

25

Table 1b - Dynamically vulcanized blends by twin extruder (Nylon/Rubber) Prior to any extrusion the material was prepared by first grinding the Nylon12 into powder and drying,

then the rubber was pre-weighed and frozen with dry ice, ground with 4mm sieve and while still frozen

the components were pre-weighed and added to the frozen rubber. The contents were shaken well and

spread out on the bench to thaw and dry. Subsequently add the parts together and pour into twin feeder

and extrude. After the first process the twin feeder is no longer required.

Components

Blend ID / Injection Moulded ID

070312-1 070312-2 070312-3 070312-4 070316-1 070316-2 070316-3 070316-4

070307-1 070308-1 070308-2 070309-1 070314-1 070315-1 070315-2 070316-1

Nylon12 (L16) 40.0phr 40.0phr 40.0phr 40.0phr 30.0phr 30.0phr 30.0phr 30.0phr

ChloroButyl1068 60.0phr 60.0phr 60.0phr 60.0phr 70.0phr 70.0phr 70.0phr 70.0phr

Naugard445 0.60phr 0.60phr 0.60phr 0.60phr 0.60phr 0.60phr 0.60phr 0.60phr

Stearic Acid 150 1.44phr 1.44phr 1.44phr 1.44phr 1.44phr 1.44phr 1.44phr 1.44phr

Paricin Wax 285 0.55phr 0.55phr 0.55phr 0.55phr 0.55phr 0.55phr 0.55phr 0.55phr

ZDEDC - - - - - - - -

Zinc Oxide 103 3.60phr 3.60phr 3.60phr 3.60phr 3.60phr 3.60phr 3.60phr 3.60phr

Zinc Oxide 172 - - - - - - - -

Sulphur 1.44phr 1.44phr 1.44phr 1.44phr 1.68phr 1.68phr 1.68phr 1.68phr

MBTS 0.54phr 0.54phr 0.54phr 0.54phr 0.54phr 0.54phr 0.54phr 0.54phr

TMTD 1.08phr 1.08phr 1.08phr 1.08phr 1.08phr 1.08phr 1.08phr 1.08phr

Clay I.30E - - - - - - - -

Processed 1X 2X 3X 4X 1X 2X 3X 4X

Components

Blend ID / Injection Moulded ID

070511-1 070511-2 070511-3 070511-4

070503-1 070508-1 070508-3 070511-1

Nylon12 (L25) 40.0phr 40.0phr 40.0phr 40.0phr

ChloroButyl1068 60.0phr 60.0phr 60.0phr 60.0phr

Naugard445 0.60phr 0.60phr 0.60phr 0.60phr

Stearic Acid 150 1.44phr 1.44phr 1.44phr 1.44phr

Paricin Wax 285 0.55phr 0.55phr 0.55phr 0.55phr

ZDEDC - - - -

Zinc Oxide 103 3.60phr 3.60phr 3.60phr 3.60phr

Zinc Oxide 172 - - - -

Sulphur 1.44phr 1.44phr 1.44phr 1.44phr

MBTS 0.54phr 0.54phr 0.54phr 0.54phr

TMTD 1.08phr 1.08phr 1.08phr 1.08phr

Clay I.30E - - - -

Processed 1X 2X 3X 4X

Appendix 1

Solvent Resistance and Mechanical Propertiesin Thermoplastic Elastomer Blends Preparedby Dynamic Vulcanization

J. D. (Jack) Van Dyke,1 Marek Gnatowski,2 Andrew Burczyk3

1Department of Chemistry, Trinity Western University, Langley, British Columbia, V2Y 1Y1 Canada2Polymer Engineering Co. Ltd., Burnaby, British Columbia, V5B 3A6 Canada3DRDC Suffield, Box 4000, Station Main, Medicine Hat, Alberta, T1A 8K6 Canada

Received 28 June 2007; accepted 20 December 2007DOI 10.1002/app.28149Published online 21 April 2008 in Wiley InterScience (www.interscience.wiley.com).

ABSTRACT: Dynamic vulcanization was used to preparethermoplastic elastomer blends of nylon (polyamide), poly-propylene (PP) and polybutylene terephthalate thermo-plastics with chlorobutyl (CIIR) and nitrile (NBR) rubbers.Mechanical properties of the blends were correlatedagainst composition. Although hardness and tensilestrength increase with increasing thermoplastic content forall blends, elongation at break values initially decrease andthen increase in the range of 20–40% thermoplastic. Forvarious blend compositions, the swelling behavior wasevaluated with solvents that are able to dissolve theuncured rubber portion but not the thermoplastic compo-nent of the mixtures. All five systems showed swellingindex values that were substantially less than the calcu-lated ‘‘theoretical’’ values of swelling index. This was

attributed to a caging effect of the thermoplastic compo-nent on the rubber phase, which restricts access of solventand swelling of the rubber phase. In turn, this affects thesolvent resistance of the blend. Some of the blends wereevaluated by differential scanning calorimetry to assess thecompatibility of the components in the blend. scanningelectron microscopy was also used to determine the degreeof compatibility of the two phases generated in the mixingprocess. � 2008 Wiley Periodicals, Inc. J Appl Polym Sci 109:1535–1546, 2008

Key words: blends; dynamic vulcanization; polyamide;nylon; polypropylene; butyl rubber; nitrile rubber; poly-butylene terephthalate; mechanical properties; differentialscanning calorimetry; electron microscopy

INTRODUCTION

Over the past 2 decades high shear melt mixing hasbecome an important method to prepare a varietyof blends of thermoplastics and vulcanizable elasto-mers, both in the presence and absence of a curingsystem for the rubber phase. Unique blend composi-tions are now possible, some of which are commer-cialized, with a multiplicity of properties that reflectthe component elastomers and thermoplastics inthese blends. Thermoplastic elastomers (TPE) madefrom two or more blend components are of parti-cular interest, and a wide variety of interestingthermoplastic/rubber combinations have now beenprepared and summarized in several review articles.1–4

Commercial thermoplastics used in these studiesinclude polypropylene (PP), polyamides (nylon, PA),and polyesters such as polyethylene terephthalate(PET) and polybutylene terephthalate (PBT). Com-mercial rubbers include butyl (IIR), ethylene-propyl-ene (EPDM), and nitrile (NBR) rubbers. Several stud-ies cover blends of PP with IIR,5,6 EPDM,1,7,8 and

NBR.2,9–12 PA compositions have been prepared withNBR,2,13–15 EPDM,16–19 acrylate,20,21 and variousbutyl rubbers.22–27 PBT has been blended with oxa-zoline-modified nitrile rubber.28

In the absence of a curing system, the phase mor-phology of a blend is determined by a numberof factors, including the relative concentrations ofthe polymeric components, the interfacial tensionbetween them, the conditions used to process themixture, and the viscosity differences between thecomponents.29 Addition of compatibilizing agentscan significantly reduce the dimensions of the dis-persed phase in some systems.16

Dynamic vulcanization, which results in curing ofthe rubber component during the mixing process, isa method used to overcome a lack of stability insome thermoplastic elastomeric blends, particularlyat elevated temperatures. Crosslinking in the rubberphase during preparation of a blend reduces the sizeof the rubber particle,30 and inhibits reagglomerationof the rubber particles during cool down times aftermixing has stopped, as well as in subsequent use ofthe blend at higher temperatures.31 During the mix-ing process the melt viscosity of the rubber phaseincreases dramatically in relation to the thermoplas-tic phase, which enables the thermoplastic phase to

Correspondence to: J. D. Van Dyke ([email protected]).

Journal of Applied Polymer Science, Vol. 109, 1535–1546 (2008)VVC 2008 Wiley Periodicals, Inc.

form the continuous phase with relatively small pro-portions of plastic in the blend.32 Materials of thisnature can be readily recycled after regrinding,largely due to the fact that, although the vulcanizedrubber particles physically interact with each otherin the blend to form a loose rubber network, theseinteractions easily disintegrate during melt-repro-cessing. The effect of morphology on the propertiesof some thermoplastic vulcanizates, and the mechan-ical and chemical factors affecting the morphology,are now becoming understood.10,15,19,33–35

The optimum choices for rubber, plastic, and cur-ing systems in blends made by dynamic vulcaniza-tion have been the subject of several articles byCoran’s group.2,3,33,36 Dynamic vulcanization oftenproduces materials having superior properties overblends containing uncured mixtures or block copoly-mer-type thermoplastic elastomers.1,2,5,37 Many pre-viously difficult combinations of materials are nowpossible, particularly when compatibilizing agentsare also incorporated into the blend.1 Materials ofthis nature generally show superior properties inpermanent set, tensile strength and elongation, fa-tigue resistance, hot-oil resistance, melt strength, andthermoplastic fabricability.37

In previous studies undertaken on blends of PAand butyl rubber in our laboratories,25–27 it wasshown that these polymers, although normally in-compatible, can be mixed in a high shear environ-ment, with and without the presence of curingagents. The greatest compatibility occurs with CIIR.The high shear environment seems responsible forproducing an interaction between the polyamide andrubber components during processing, resulting inthe presence of small quantities of block or graftpolymers in the system, which can act as compatibi-lizing agents.

Exposure to solvents has become a useful tool inour laboratories to understand the morphologicalchanges taking place in blends over a range of com-positions. It has been observed that experimentalvalues of the solvent swelling indices for blends ofCIIR and PA are much less than values that wouldbe calculated for mixtures of rubber and plastic thathave not gone through a high shear blending pro-cess. A similar observation was made by Jha andBhomick for nylon/acrylate blends.20 This effect maybe due to restrictions a continuous thermoplasticphase places on the swelling of the crosslinked rub-ber particles. There is some evidence that phaseinversion in PA/CIIR blends may occur as low as25% PA, which would make this effect observablewhenever the thermoplastic composition exceedsthis relatively low value.

The present study was undertaken to determine ifthe observation of a continuous PA phase as low as25% in PA/CIIR blends could be generalized and

applied to a variety of other rubber/plastic combina-tions prepared by dynamic vulcanization. Such ob-served phenomena may have significant practicalvalue in relation to overall chemical resistance inblends, particularly when the rubber phase is vul-nerable to attack. Three thermoplastics PA, PP, andPBT were studied in combination with two rubbers,CIIR and NBR, and five blend combinations wereproduced at different proportions of rubber andplastic. The completed blends were molded, andtested for mechanical properties, exposure to sol-vents, differential scanning calorimetry (DSC) andscanning electron microscopy (SEM).

EXPERIMENTAL

Materials used

Polyamide-12 (Grilamid L16) was obtained fromEMS-American Grilon (Sumter, SC), polypropylene(Profax 6524) from Exxon Mobil Chem (Houston,TX), and polybutylene terephthalate (PBT 1700A)from Celanex Ticona (Bishop, TX). Chlorobutyl 1068rubber was supplied by Exxon Chemical (Sarnia,ON, Canada), and nitrile rubber (Krynac 3345C) byBayer Chemical (Sarnia, ON, Canada). Zinc oxide(ZOCO 172) was supplied by Zochem (Brampton,ON, Canada), zinc diethyldithiocarbamate (ZDEDC)by R.T Vanderbilt (Norwalk, CT), peroxide (Trigonox101-45B-pd) by Akzo-Nobel (McCook, IL), and anti-oxidants (Flectol TMQ by Flexys America (Akron,OH), Naugard PHR by Crompton (Middleburg, CT),and A/O 2264 by Aldrich (Milwaukee, WI)). Stearicacid (Emersol 150) was supplied by Cognis Canada(Toronto, ON), Paracin 285 wax by CasChem (Ba-yonne, NJ), Sartomer (SR-525) by Sartomer (Wes-chester, PA), and magnesium oxide (Maglite D)by the C.P. Hall Co (Memphis, TN). Reagent-gradehexane was supplied by Anachemia (Montreal, QC,Canada), and reagent-grade chloroform by CaledonLabs (Georgetown, ON, Canada).

Curing systems employed in this study

Chlorobutyl rubber-based systems

A ZDEDC/ZnO-based curing system was used forpure rubber compounds and all blends containingthis rubber. The proportions of the curing compo-nents were 2.2 phr of ZDEDC (on rubber), and 6.70phr ZnO (based on total polymer).

Nitrile rubber-based systems

For blends with PA, the curing system employed2.50 phr of Sartomer and 2.1 phr of peroxide (bothbased on rubber); for blends with PP, the curing sys-

1536 VAN DYKE ET AL.

Journal of Applied Polymer Science DOI 10.1002/app

tem employed 2.50 phr of Sartomer (based onrubber) and 2.50 phr of MgO (based on total poly-mer). For blends with PBT, the curing systememployed 1.66 phr of Sartomer (based on rubber).

Complete formulations are listed in Tables I–V.

Mixing procedure

All blends were made in a 258 cm3-capacity 5 HPPlasticorder EPL-V5502 equipped with Prep Mixertype R.E.E.6 and type 808-2504/PSI/DTI Rheometer

TABLE IProperties of Polyamide/Chlorobutyl Rubber Blendsa,b

Blend ratio(PA/CIIR)

Mechanical properties Effect of exposure to solvents

Ultimatestrength(MPa)c

Elong. atbreak (%)d,e

Modulus(Mpa)f

Shore Dhardnessg

Swellingindex

(hexane)h

Swellingindex

(CHCl3)i

% Insol.(hexane)j

% Insol.(CHCl3)

k

0/100 2.93 6.51 99.9 99.615/85 1.8 252 3.7 12 3.59 8.33 68.4 67.020/80 4.7 168 16.3 22 2.55 5.60 81.3 78.925/75 7.0 165 35.8 30 1.88 3.90 92.0 90.830/70 9.7 196 74.4 37 1.59 3.18 95.6 94.335/65 11.0 210 77.5 46 1.45 2.66 97.2 97.240/60 12.3 195 91.7 49 1.34 2.34 99.1 98.350/50 14.6 94 2.06 97.2100/0 35.3 110 1.00 1.08 99.5 104.8

a Blends prepared by dynamic vulcanization, formulation: nylon 12 (L16), chlorobutyl 1068, ZDEDC 2.2 phr (on rubber),[ZnO 6.70 phr, stearic acid 1.44 phr, paracin wax 0.55 phr, (based on total polymer)].

b Samples injection molded, except for 0/100 which was compression molded.c Average SD of 4%.d Elongation at break values based on bench marks.e Average SD of 5%.f Average SD of 13%.g Average SD of 4%.h Average SD of 0.7%.i Average SD of 1.3%.j Average SD of 0.2%.k Average SD of 0.4%.

TABLE IIProperties of Polypropylene/Chlorobutyl Rubber Blendsa,b

Blend ratio(PP/CIIR)




Modulus(Mpa)f

Shore Dhardnessg

Swellingindex

(hexane)h

Swellingindex

(CHCl3)i

% Insol.(hexane)j

% Insol.(CHCl3)

k

0/100 2.93 6.51 99.9 99.617.5/82.5 3.1 136 13 20 2.62 5.16 87.6 86.820/80 3.6 146 19 25 2.45 5.05 89.2 87.825/75 4.4 128 30 26 2.30 4.48 89.3 88.030/70 5.5 124 41 31 2.09 3.84 91.7 91.635/65 7.9 198 67 38 1.87 3.43 94.3 93.040/60 9.1 244 79 43 1.77 2.97 94.5 94.250/50 12.4 278 n/a 2.47 95.7100/0 31.8 138 71 n/a 1.26 94.1 99.7

a Blends prepared by dynamic vulcanization, formulation: polypropylene, chlorobutyl 1068, ZDEDC 2.2 phr (on rubber),[ZnO 6.70 phr, stearic acid 1.44 phr, paracin wax 0.55 phr, A/O2264 0.33 phr (based on total polymer)].

b Samples injection molded, except for 0/100 which was compression molded.c Average SD of 4%.d Elongation at break values based on bench marks.e Average SD of 5%.f Average SD of 13%.g Average SD of 4%.h Average SD of 0.7%.i Average SD of 1.5%.j Average SD of 0.4%.k Average SD of 0.4%.

PROPERTIES OF TPE BLENDS 1537


and temperature control (Brabender Instruments,Hackensack, NJ).

Blends based on polyamide

PA was first added at 30 rpm mixing speed to theBrabender Mixer at a target temperature of 1908C, and

allowed to melt for 2 min. The rubber was then addedalong with stearic acid and wax, and the mixing speedwas increased to 65 rpm. Mixing was continued for anadditional 6 min. After a total mixing time of 8 min,the active curing agent was added and allowed to mixfor 4.5 min (total mixing time of 12.5 min). The blendwas then removed from the mixer and cooled.

TABLE IIIProperties of Polyamide/Nitrile Rubber Blendsa,b

Blend ratio(PA/NBR)

Mechanical propertiesEffect of exposure to

solvents



Modulus(Mpa)f

Shore Dhardnessg

Swellingindex

(CHCl3)h

% Insol.CHCl3

i

0/100 2.7 140 1.8 21 5.99 96.615/85 7.9 129 13 35 5.48 95.320/80 9.1 136 16 39 4.70 94.725/75 12.2 173 16 41 4.77 95.330/70 14.0 179 16 45 4.19 94.835/65 16.4 170 25 49 3.75 93.940/60 18.2 190 23 49 3.37 97.0100/0 1.08 104.8

a Blends prepared by dynamic vulcanization, formlation: nylon 12 (L16), nitrile, [Sartomer 2.50 phr, peroxide 2.1 phr,antioxidant TMQ 1.66 phr, all based on rubber], [stearic acid 1.44 phr, paracin wax 0.55 phr, based on total polymer].

b Samples injection molded, except for 0/100 which was compression molded.c Average SD of 4%.d Elongation at break values based on bench marks.e Average SD of 5%.f Average SD of 13%.g Average SD of 4%.h Average SD of 2.4%.i Average SD of 1.9%.

TABLE IVProperties of Polypropylene/Nitrile Rubber Blendsa,b

Blend ratio(PP/NBR)




Modulus(Mpa)f

Shore Dhardnessg

Swellingindex

(CHCl3)h

% Insol.(S.I.) CHCl3

i

0/100 2.3 572 0.7 12 34.61 45.715/85 2.6 28 16.9 27 10.59 87.120/80 2.7 18 22.6 29 9.83 87.725/75 3.9 30 33.6 33 8.75 87.430/70 4.9 38 43.5 38 7.75 87.335/65 7.2 30 78.1 41 7.14 88.140/60 5.9 40 54.9 46 6.23 87.350/50 11.1 42 4.80 91.0100/0 31.8 138.0 71 1.26 99.7

a Blends prepared by dynamic vulcanization, formlation: polypropylene, nitrile, [sartomer 2.50 phr, A/O 2264 1.67 phr,naugard PHR 0.83 phr, based on rubber], [stearic acid 1.44 phr, paracin wax 0.55, MgO 2.50 phr, based on total polymer].




Blends based on polypropylene

PP was first added at 30 rpm mixing speed to theBrabender Mixer at a target temperature of 1908C,and allowed to melt for 4 min, with antioxidantaddition at 3 min. Rubber was added at 4 min andadditional antioxidant along with stearic acid andwax at 5 min, and the mixing speed was increasedto 65 rpm. Metal oxides were added at 7 min, andSartomer (when needed) at 8 min. Total mixing timewas 12 min. The blend was then removed from themixer and cooled.

Blends based on polybutylene terephthalate

PBT was first added at 30 rpm mixing speed to theBrabender Mixer at a target temperature of 2358C,and allowed to melt for 3 min. Rubber and antioxi-dant were added over a period from 3 to 5 min, andthe mixing speed was increased to 65 rpm. Stearicacid, wax, and Sartomer were added over the periodfrom 5 to 6 min. Total mixing time was 9 min. Theblend was then removed from the mixer and cooled.

Pure rubber samples

For each blend combination investigated in thisstudy, a pure rubber composition was prepared witha formulation that was identical to blends containingthis rubber.

Chlorobutyl rubber was masticated at 25 rpm anda target temperature of 508C for 3 min, after which

stearic acid and zinc oxide were added. At the 8min-mark ZDEDC was added and mixing was con-tinued for an additional 2 min. The total mixingtime was 10 min. After blending was complete, thecompound was compression molded at 1608C for 30min.

Nitrile rubber was masticated at 25 rpm and a tar-get temperature of 908C for 3 min, after which A/Owas added. Stearic acid was added at the 4 min-mark, Paracin wax at 4.5 min, SR-525 at 6 min, andperoxide at 8.5 min. Mixing was continued for anadditional 3.5 min for a total blend time of 12 min.After blending was complete, the compound wascompression molded at 2108C for 30 min.

Testing and characterization

Mechanical properties

In all blends the mechanical properties were testedon specimens prepared directly by injection moldingusing an Arburg type 200U-D or 221K instrument.In PA/CIIR blends all zones were adjusted to 1808C,while in PA/NBR blends the zones were set at 215,225, and 1808C, respectively. In PP-based blends,zones were adjusted to 190, 200, and 2208C; in PBT-based blends, the zones were adjusted to 255, 290,and 2308C. A computerized Instron 4400 UniversalTesting Machine was used to determine stress/straincharacteristics on injection-molded samples accord-ing to the American Society for Testing and Materi-als procedure D638 (ASTM D638). Hardness values(Shore A and D) were determined by ASTM D2240.

TABLE VProperties of Polybutylene Terephthlate/Nitrile Rubber Blendsa,b


Blend ratio(PBT/NBR)



Modulus(Mpa)f

Shore Dhardnessg

Swellingindex

(CHCl3)h

% Insol.(S.I.) CHCl3

i

0/100 2.3 572 0.7 12 24.43 79.015/85 16.16 89.220/80 2.6 36 13.2 29 9.39 86.625/75 3.6 46 17.4 31 7.97 93.130/70 7.2 96 26.7 39 6.29 94.035/65 9.4 124 36.0 40 5.59 94.840/60 12.1 138 48.1 42 4.95 95.350/50 17.9 198 3.39 97.6100/0 53.1 44 458.4 74 1.15 102.4

a Blends prepared by dynamic vulcanization, formulation: PBT, nitrile, [stearic acid 1.44 phr, paracin wax 0.55 phr,based on total polymer], [antioxidant TMQ 1.56 phr, sartomer 1.56 phr, based on rubber].




Swelling index and percentage insolubles

For swelling index determination on plastic/rubberblends, a molded or pressed specimen, � 1 cm2 and1.5-mm thick, was immersed in reagent-grade hex-ane or reagent-grade chloroform for 4 days to obtainequilibrium. (Equilibrium swelling in rubber samplesand blends is reached in less than 1 day, and thick-ness of samples has only a marginal effect on thefinal result.27) The swelling index of a blend samplewas determined by comparison of the weight of theswollen sample to its weight after drying to constantweight. The % insolubles were determined by com-parison of the weight after drying to the originalweight of the sample.

Differential scanning calorimetry

Several rubber/plastic blends prepared by injectionmolding were analyzed on a Perkin–Elmer DSC-7instrument (Perkin–Elmer Cetus Instruments, Norwalk,CT) according to ASTM D 3417. The melting tem-perature and enthalpy of fusion values for thethermoplastic phase were recorded for each sample.If multiple peaks occurred, the melting temperaturereferred to the highest (second) peak. For PA/CIIRblends, it has been shown by repetitive results inour laboratories that the values of melting tempera-ture and enthalpy of fusion are within experimentalerror of each other for injection molded samples andgranulated pellets.

Scanning electron microscopy

SEM was conducted using a variable pressure LEO1455VP microscope (Meridian Scientific Services,Stittsville, ON, Canada). Specimens were preparedeither by cutting with a sharp blade at room temper-ature, or fracturing at low temperature. After expo-sure to OsO4, the blends were mounted on alumi-

num stubs with carbon paint, and examined withoutcoating at low pressure using a Robinson BackscatterDetector.

RESULTS AND DISCUSSION

Mechanical properties of blends

Tables I–V list the results of dynamic vulcanizationexperiments on PA/CIIR, PP/CIIR, PA/NBR, PP/NBR, and PBT/NBR blends, with the proportion ofthe hard phase ranging from 15–50% thermoplasticfor most combinations. Values for 100% rubber and100% plastic compositions are also listed in thesetables, each obtained under similar heat and/orchemical treatment as blends of the two.

In all five plastic/rubber combinations, the tensilestrength values increase as the proportions of ther-moplastic increase in the blends (Fig. 1). As well, themodulus and hardness values increase with increas-ing proportion of thermoplastic. Elongation at breakvalues, on the other hand, drop rapidly as thermo-plastic is introduced to a pure rubber compoundand reach a minimum value at � 20–25% plastic. Athigher levels of thermoplastic all blends show con-sistent increases in elongation at break values untilblend proportions reach about 50 : 50. (see Figs. 2–6).

The elongation at break results in this study paral-lel the results of Kumar et al.13 on PA/NBR blends,where increasing PA content produced increasing %elongation values up to 60% PA. Another study byOderkerk et al.18 on PA/EPDM blends suggests thatthin ligaments of the Nylon 6 matrix deform plasti-cally during stretching, and are part of the elasticrestoring forces in the rubber particles and the Ny-lon matrix after stress is relieved from test samples.A similar observation has been made by Van Duin38

for PP/EPDM blends. Applying these observationsto the present study, thin plastic layers between rub-ber particles begin to dominate with increasing pro-portions of the thermoplastic component. As elastic

Figure 1 Tensile strength versus % thermoplastic. [Colorfigure can be viewed in the online issue, which is availableat www.interscience.wiley.com.]

Figure 2 Swelling index and elongation at break for PA/CIIR blends. [Color figure can be viewed in the onlineissue, which is available at www.interscience.wiley.com.]



extension and recovery is greatest in thin PA sec-tions, their presence at higher plastic levels mayincrease the ability of the blend to elongate undertension.

The physical properties in all of the blend combi-nations considered in this study vary from soft andrubbery in blends enriched in rubber, to hard andplastic-like in blends enriched in thermoplastic.Materials that can serve as useful thermoplastic elas-tomers generally have properties that are intermedi-ate between those of the rubber and plastic compo-nents. Our results suggest that the best compromisebetween toughness, hardness, and extensibility inthe blends that were studied occurs in the range of30–40% thermoplastic.

Exposure of blends to solvents

In addition to physical properties, Tables I–V list theeffect of exposure of the blends to various solvents.The values of swelling index and % insolubility ineach of these tables represent equilibrium values,obtained after immersion in the solvent for 4 days.(Equilibrium values are generally achieved in lessthan 1 day.27) All blends that contained CIIR were

exposed to both hexane and chloroform, as both areexcellent solvents for uncured CIIR. Referring toTables I and II it can be seen that values of % insolu-bility in CIIR-containing blends are fairly equivalentfor both solvents, whereas values of swelling indexobtained with chloroform are much higher thanhexane-based values. The disparity in swelling indexvalues can be attributed primarily to differences indensity between the two solvents. NBR-containingblends were not exposed to hexane, as this solvent isa nonsolvent for uncured NBR, while chloroform isone of the better solvents for NBR.

Percent insolubility values increase with higherproportions of thermoplastic for all blend combina-tions considered in this study. Compounds contain-ing 100% CIIR show high values of % insolubilityand appear to be the exception to this result, butthis is explained by the different preparation methodused for pure rubber samples, i.e., compressioncuring.

Swelling index and elongation at break values areplotted versus composition in Figures 2–6 for allcombinations of rubber and plastic. Each figure alsoshows the straight line theoretical swelling index

Figure 3 Swelling index and elongation at break for PP/CIIR blends. [Color figure can be viewed in the onlineissue, which is available at www.interscience.wiley.com.]

Figure 4 Swelling index and elongation at break for PA/NBR blends. [Color figure can be viewed in the onlineissue, which is available at www.interscience.wiley.com.]

Figure 5 Swelling index and elongation at break for PP/NBR blends. [Color figure can be viewed in the onlineissue, which is available at www.interscience.wiley.com.]

Figure 6 Swelling index and elongation at break forPBT/NBR blends. [Color figure can be viewed in the onlineissue, which is available at www.interscience.wiley.com.]



predicted for simple dry-mixtures of the two compo-nents in the blend. As % thermoplastic increases inblends of PA/CIIR, PP/CIIR, PA/NBR, PP/NBR,and PBT/NBR, the swelling index values fall signifi-cantly below the theoretical line. This behavior paral-lels previous observations on PA/CIIR blends in thislaboratory.27 This has also been observed in nylon-6/acrylate rubber blends by Jha and Bhowmick, whoattributed behavior of this nature to the restrictionplaced by the nylon-6 phase on the swelling of theacrylate rubber particles, as well as a reductionin the mobility of acrylate rubber chains created bynylon grafts at the acrylate/nylon interface.20 Mousahas also observed that solvent swelling of the rubberphase in PP/EPDM blends is limited by the thermo-plastic phase.7

The swelling index behavior for several of theblends in this study suggests that swelling index val-ues fall below the theoretical line after a minimum% thermoplastic has been achieved. The suggestedcomposition range over which phase inversion takesplace in Figures 2–6 is indicated by hashed lines.Phase inversion may begin as low as 10–20% ther-moplastic in several blends (particularly PP and PBTcontaining blends). In PA-containing blends, phaseinversion more likely occurs between 20 and 30%thermoplastic. In all cases phase inversion appearsto be accompanied by both a reduction in swellingindex values and an increase in elongation at breakvalues. Phase inversion at low % thermoplastic hasbeen observed in at least one other system. Usingrheology, Joubert et al.34 observed that phase inver-sion took place with 20% PP in a PP/EVA system.

A comparison of dynamic vulcanization to staticvulcanization was provided in one case for a 30/70PA/CIIR blend using identical formulations for bothmethods of vulcanization. The swelling index of thestatic blend is higher than the one produced underdynamic vulcanization (Fig. 2), which is likely dueto the fact that the morphology of the static sampleconsists primarily of a rubber continuous phase. Therubber phase in this sample will not experience

nearly as great a restriction on its swelling behavioras would a dynamically vulcanized sample of simi-lar composition in which the thermoplastic phasehas become the continuous phase.

Critical surface tension for wetting and solubilityparameters provide an indication of compatibility inpolymer systems, and values of these parameters arelisted in Table VI. Higher degrees of compatibilitybetween the two phases are expected to decrease theparticle size of the dispersed phase. This, in turn,may have an effect on the behavior of the swellingindex versus composition line. For example, a highlevel of compatibility is suggested for PA/NBRblends, which may be one reason why swellingindex values do not deviate greatly below the theo-retical line in this system, in contrast to the otherblend combinations.

Results of DSC experiments

The DSC results on pure resins and 40/60 plastic/rubber blends, produced from reheating peaks, areshown in Table VII. For each of the blends, the ther-moplastic phase displays a discrete melting tempera-ture, indicating that plastic and rubber phases areseparate in all of the blends. A typical DSC plot fora PA/CIIR combination is included in Figure 7.Adding CIIR or NBR rubber to two of the three ther-moplastics used in this study causes a reduction inthe melting temperature of the plastic phase, indicat-ing that the thermoplastic phase is affected duringintensive mixing of these blends. The enthalpy offusion values for each of the thermoplastic phasesare fairly similar to those of their parent values,except for PBT/NBR blends, which may be due todegradation. Possible effects on the thermoplasticphase that may be taking place during dynamic vul-canization are MW reduction, graft formation, andchanges in crystallization behavior. Previous resultsin this laboratory suggest that grafting between PAand butyl rubber takes place during blending.25 Nas-kar et al.40 also observed PP-EPDM graft links in the

TABLE VICompatibility Factors for Polymers Used in the Study

Polymer

Critical surfacetension forwettinga

(mN/m)

Solubilityparameterb

(MPa)1/2

PA 39 19PP 28 16.5PBT 39 21.6CIIR 27 16.7NBR 39 21.4

a Values taken from Ref. 1, this paper.b Values taken from Ref. 39, this paper.

TABLE VIIDSC Results—Thermoplastic Phase

Resin or blendcombinationa Tm (8C) DHf (J/g plastic)

PA 178.7 60.6PA/CIIR 174.9 58.1PA/NBR 176.5 58.5PP 163.3 80.9PP/CIIR 161.6 83.1PP/NBR 161.5 80.6PBT 223.1 38.1PBT/NBR 224.4 113.9

a Blend compositions are 40/60 plastic/rubber.



dynamic vulcanization of PP/EPDM blends. Lindseyet al. observed lower Tm values for LDPE in DSCcooling scans of LDPE/EPDM blends, and attributedthis to partial solubilization of EPDM rubber withLDPE.41 Their explanation may have only partialrelevance in polymer blends such as these, wherethe polymeric substituents may have completely dif-ferent solubility parameters.

Scanning electron microscopy onrubber/plastic blends

Figures 8–11 contain SEM micrographs of dynami-cally vulcanized blends of PA, PP, and PBT withCIIR and NBR. As can be seen, blends that contain15–20% thermoplastic largely consist of a continuousphase based on rubber. There is some evidence offormation of an interlocking network at 20%. In con-trast, blends with 40% thermoplastic all show a dis-crete rubber phase with an average rubber phaseparticle size in the range of 1–3 lm for PA/NBRblends, 10–30 lm for PP/NBR blends and 0.5–3 lmfor PBT/NBR blends. Blends of thermoplastics withCIIR are more difficult to observe, because theirlower level of unsaturation makes them more diffi-cult to stain. As well, the dense particles of ZnOused for curing make it somewhat difficult to see therubber particles. Nevertheless, it appears that therubber phase is of the order of 2–4 lm in PA/CIIRblends and 1–3 lm in PP/CIIR blends. The particlesize results suggest that the size of the discrete rub-ber phase at 40% thermoplastic is smaller when thecomponents are matched in interfacial tension andsolubility parameter, as expected. Thus, higher com-patibility of the components gives rise to smallerdiscrete phase size, as is suggested for blends in theabsence of dynamic vulcanization.14 Blends contain-ing smaller rubber particles will, on average, allowfor greater surface contact between the rubber par-ticles in the blend, thus enhancing the interaction ofthe dispersed rubber phase in the blend.

The results of SEM and exposure to solvents pres-ent a consistent picture of the morphological changestaking place in a variety of dynamically vulcanized

Figure 8 SEM of etched specimens of dynamically vul-canized PA/NBR blends (a) PA/NBR ratio: 15/85, (b) 20/80, and (c) 40/60.

Figure 7 DSC plot of a 40/60 PA/CIIR blend.



rubber/plastic blends over the range of 0–50% ther-moplastic. As thermoplastic is introduced to therubber compound, the continuous phase undergoes

phase inversion from rubber to plastic over a rangeof 10–30% thermoplastic, depending on the thermo-plastic/rubber combination. When the thermoplasticcomponent forms the continuous phase, the discreterubber phase is provided with a plastic sheath sur-rounding the discrete rubber particles, which canrestrict its volume expansion in the presence of sol-vents compatible with the rubber phase. A result ofthis nature might be expected for dynamic vulcani-zation. Although the swelling pressure in cross-linked rubber systems can become very high,42 thecounter-pressure of the continuous plastic phase inthese blends acts as a negative influence in the vol-ume expansion of the rubber phase. The success ofthe rubber particles to expand in the presence of sol-vents will depend on the choice of plastic and rub-ber, as well as shear history, presence of compatibi-lizing agents, and other factors that can affect themorphology of the blends.

Figure 10 SEM of etched specimens of dynamically vul-canized PBT/NBR blends (a) PBT/NBR ratio: 20/80 and(b) 40/60.

Figure 9 SEM of etched specimens of dynamically vul-canized PP/NBR blends (a) PP/NBR ratio: 15/85, (b) 20/80, and (c) 40/60.



Solvent resistance is an important issue in TPEblends, particularly those formed from mixtures oftwo or more component polymers. Although over-all solvent resistance should be best when both therubber and plastic components are resistant to sol-vents, an advantage is gained for mixtures of thistype when they are exposed to solvents specific tothe rubber component. If the rubber particles aresurrounded by a thermoplastic sheath in blends ofthis nature, the TPE blend can be protected tosome degree from attack by solvents that areaggressive to the rubber phase. Preliminary tests onNBR-containing blends indicate that solvents, whichattack the rubber phase are much less effectivewhen thermoplastics are introduced as blendagents. Thus, the barrier properties of blends canbe enhanced by the appropriate choice of thermo-plastic.

CONCLUSIONS

1. Dynamic vulcanization was used to produce avariety of rubber plastic blends in systems con-sisting of PA/CIIR, PP/CIIR, PA/NBR, PP/NBR,and PBT/NBR.

2. In all blends, the ultimate tensile strength andhardness values increase as the proportion ofthermoplastic is increased, in the range of 0–50% thermoplastic.

3. Elongation at break values in all blends reach aminimum at 15–25% thermoplastic, which likelycorresponds to the composition where thephase volume of the plastic phase is largeenough to cause phase inversion.

4. In all of the tested blends, when the composi-tion favors a continuous thermoplastic phase,the equilibrium swelling index values of theblends are significantly less than the expected‘‘theoretical’’ values, based on blend composi-tion only. This is attributed to a ‘‘caging effect’’of the thermoplastic phase on the rubber phaseat higher thermoplastic compositions.

5. DSC experiments reveal a reduction of up to2.58C in melting temperature of the thermoplas-tic phase in several of the blends, indicatingthat the plastic phase undergoes physical andchemical changes during the dynamic vulcani-zation process.

6. Etched surface micrographs of several plastic/rubber blends by SEM show that phase inversionoccurs in the range of 20–40% thermoplastic.

7. At similar plastic/rubber proportions, increasedcompatibility in blends can be correlated withreduced particle size in the discrete phase. In-creased compatibility may produce less cagingeffect on the rubber phase.

The authors express their appreciation to Dave Lesewickand Christine Mah of Polymer Engineering Co. Ltd., andto Leanne Edwards of Trinity Western University. We alsoexpress appreciation to Bruce Kaye of Esquimalt DefenseResearch Detachment for sample evaluation by SEM, andto all of the material suppliers listed in the experimentalsection of this article.

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cling Technol 2005, 21, 1.36. Coran, A. Y.; Patel, R. Rubber Chem Technol 1981, 54, 892.37. Coran, A. Y. Rubber Chem Technol 1995, 68, 351.38. Van Duin, M. Macromol Symp 2006, 233, 11.39. Brandrup, J.; Immergut, E. H.; Grulke, E. A. Polymer Hand-

book, 4th ed.; Wiley: New York, 1999; p VII/702.40. Naskar, K.; Noordermeer, J. W. M. J Appl Polym Sci 2006, 100,

3877.41. Lindsay, G. A.; Singleton, C. J.; Carman, C. J.; Smith, R. W. In

Multiphase Polymers; Cooper, S. L.; Estes, G. M., Eds.; Ameri-can Chemical Society: Washington, DC, 1979; p 367.

42. Rigbi, Z. Kautshuk und Gummi Kunststoffe 1991, 44, 915.



Appendix 2

NOVEL NYLON/HALOGENATED BUTYL RUBBER BLENDS IN PROTECTION AGAINST WARFARE AGENTS Marek Gnatowski, Polymer Engineering Co. Ltd, Burnaby, B.C., Canada J.D. (Jack) Van Dyke, Trinity Western University, Langley, B.C., Canada Andrew Burczyk, Defence R&D Canada-Suffield, Canada

ABSTRACT Novel thermoplastic material was designed for making warfare agent resistant equipment. Nylon 12/chlorobutyl blends were selected and evaluated. The evaluation included microstructure, resistance to hydrocarbon solvents, mechanical properties, and resistance to sulfur mustard penetration and reemission. It was found that a nylon/chlorobutyl rubber blend made by dynamic vulcanization may have elastomeric behaviour, good mechanical properties, and be resistant to warfare agent penetration and reemission. The material is also thermoplastic and could be processed by injection moulding or extrusion.

Biographical Note Dr. Marek Gnatowski is Technical Director of Polymer Engineering Co. Ltd., Burnaby, British Columbia, Canada. He has 36 years of experience in industrial research and development, consulting, and process control, including 25 years experience in North America in fields related to polymeric materials. This includes over 20 years work on polymer blends fro a variety of applications. He is the author of three book chapters in Plastics Waste Management, 10 papers in scientific journals, 13 conference presentations, 11 patents and 3 patent applications pending. Dr. Gnatowski has held the position of technical director of Polymer Engineering Company Ltd. in Burnaby, BC, Canada for over twenty years. The main focus of his research activities has been the response of natural and synthetic polymers to environmental exposure.

Introduction Humans and their resources can be exposed to a variety of hostile and aggressive environments due to exploration of new frontiers such as the deep underwater regions of the earth or outer space. Humans can also face natural or man made disasters, or war. In all of these situations protection of humans and their resources, such as for example food, drinking water, or equipment becomes an urgent and important issue. More recently, a potentially increasing problem could be exposure to toxic chemicals or radioactive materials due to, for example, accidents in chemical manufacturing and storage, or intentional activity. For this reason, development in protective equipment against chemical, biological, and nuclear contamination is a continuous and urgent challenge. Polymers or composites containing polymers have frequently become used as materials in the design and manufacturing of a variety of protective gear or gear parts due to certain favorable properties such as:

• Light weight

• Wide range of mechanical properties (including elastomeric)

• Resistance to wear

• Wide range of coefficient of friction

• Easy moulding

• Resistance to hostile and aggressive environment (if properly designed and selected). Properties such as light weight, elastomeric behavior, and the extremely low modulus of elasticity (softness) offered by polymers are not generally available in other materials such as metals, or ceramics and glasses. Also, easy moulding of goods by injection moulding, extrusion, or compression moulding generally favours polymeric materials, particularly thermoplastics. Some disadvantages of polymers could be their frequently seen limited chemical resistance. For this reason, during selection or designing of polymeric materials that are expected to be exposed to chemical attack, caution has to be taken. Commercially available polymers known for their resistance to warfare agents are listed in table 1 along with some other common plastics and rubbers. Table 1. Properties of selected commercial polymeric materials

Material

Mechanical Properties

Resistance to Mechanical Behaviour Processing

Friendly In Air

In water

Warfare Agents

Water* Oil and Fuels

Engineered Plastic

Elastomer

Butyl, Halogenated Butyl Rubber

IIR 2-3 4 3 4 1 1 4 2-3

Natural Rubber (polyisoprene)

NR 2-4 3 1 1-3 1 1(3)c 4 2-3

Chloroprene 4 2-4 1-2 2-3 4 1 4 2-3

Nitrile Rubber NIR 4 4 1-2 3 4 1 4 2-3

Santoprene (PP/EPDM) TPE 3 3-4 1 3 1-2 1 4 4

Polyurethane Elastomer PU 4 3-4 1-2 2-4 3-4 1 4 3-4

Polyamides (Nylons) PA 4 3(13)a 3 3(1)

a 4 4 1 3-4

Polyester (PBT, PET) PET 4 4(2)a 3 4 4 4 1 3-4

Polyvinyl Alcohol (PVOH) PVA 4 1 3 1 4 3 1 1-2b

Polystyrene PS 3-4 3-4 1 4 1 2-3 1 4

HDPE HDPE 2-3 2-3 1 4 3-4 2-3 1 4

4 – excellent 3 – good 2 – acceptable 1 – unacceptable a. immersion in hot water

b. requires modification

c. ebonite

* long term exposure

Please note that the only common elastomer that has good resistance to warfare agents is a butyl or halogenated butyl rubber. Unfortunately, manufacturing goods from this rubber requires, in most cases, a moulding process with a long production cycle, and it can not be welded. Also, limited absorption of warfare agents in the final products has been observed. Thermoplastics, with excellent resistance to warfare agent penetration and absorption, are primarily hard engineering resins such as crystalline polyamides or polyesters. As a rule of thumb, we can expect that softening of polymeric material will lead to an increase in diffusion, and absorption of the chemical compounds. This means that designing a new, softer elastomeric material that is resistant to warfare agents is a challenge, particularly when this material should be moulded as a thermoplastic resin. Another challenge is to obtain this new thermoplastic using commercially available materials.

Nylon/Halogenated Butyl Rubber Blend A natural approach seemed to be to combine the properties of an elastomer, such as butyl rubber, with one of the engineered thermoplastic resins that had excellent resistance to warfare agents and good melt processing, such as a nylon. Butyl rubber, when vulcanized and crosslinked, has reasonable mechanical properties, good warfare agent resistance, and is commercially available. Among nylon resins, polyamide 12 has received attention due its excellent mechanical and barrier properties and relatively low processing temperature, in the range of 190

o – 220

o C. This resin is also commercially available.

This mixing approach instantly creates challenges. Nylons and butyl or halogenated butyl rubbers are expected to be incompatible due to their chemical differences, which are reflected in different solubility parameters and surface energy. To obtain suitable rubber properties, including warfare agent resistance, the vulcanization process has to be employed to facilitate crosslinking. Also, a significant quantity of rubber has to be incorporated into the new material to obtain elastomeric behavior. A larger quantity of crosslinked rubber in the blend could create a problem in obtaining material with thermoplastic moulding capability and good mechanical properties. Nylon/butyl rubber blending was conducted in our laboratory using a Brabender batch blender equipped with roller blades, or a twin screw extruder. The dynamic vulcanization process was employed during the blending of nylon 12 with butyl or halogenated butyl rubbers. Dynamic vulcanization is a process where rubber is vulcanized during blending with thermoplastic resin. During the mixing process, the rubber component becomes crosslinked and suspended in the form of very small particles in thermoplastic resin as shown in schematic form in figure 1a and b, and SEM photomicrographs in figure 2a and b. This allows for the addition of a significant quantity, well over 50%, of the rubber component into the thermoplastic resin blend which would still maintain flow despite rubber vulcanization. The microstructure of this blend is also responsible for the peculiar properties of this material as will be discussed further in this paper. Figure 1. Schematics of rubber dispersions

Figure 2. SEM microphotographs of rubber dispersions

1a. Dispersion of rubber in thermoplastic resin made by blending without vulcanization

1b. Dispersion of rubber in thermoplastic resin made by the dynamic vulcanization process

2a. SEM of dispersion of rubber in thermoplastic resin made by blending without vulcanization

2b. SEM of dispersion of rubber in thermoplastic resin made by the dynamic vulcanization process

The finely dispersed rubber phase in nylon would be very difficult to achieve without good compatibility of both blend components. In the case of our nylon/rubber blend, this was most likely done through the generation of a compatibilizer in the polymer grafting reaction shown in figure 3. The presence of grafted polymers can be seen in the infrared spectrum of the non-vulcanized butyl rubber extracted from the nylon 12 blend by hexane. The weak polyamide absorption band at 1640 cm

-1 appears in the rubber spectrum as

shown in figure 4. Figure 3. Grafting reaction – molecule of butyl rubber to nylon

Figure 4. FTIR spectrum of butyl rubber extracted from blend with nylon 12

Vulcanization and Chemical Resistance Full crosslinking of the butyl or halogenated butyl rubbers blended with nylon 12 using the dynamic vulcanization process can be confirmed by comparison of insoluble content after extraction of the blend with hexanes (figure 5).

O

O

NH

NH

O

NH

CH2*

O

O

NH

NH

O

NH

+

O

O

NH

NH

O

NH

CH2*

O

O

NH

NH

O

NH

+

Figure 5. Percent of insoluble matter in non-vulcanized and vulcanized rubbers blended with nylon

0

20

40

60

80

100

120

Butyl Bromobutyl Chlorobutyl

% I

ns

olu

ble

s Non Vulcanized

Dynamically

Vulcanized

Comparison of tensile strength and elongation at break for a series of blends of nylon 12 with butyl and halogenated butyl rubbers confirmed that the most favorable mechanical properties in tension consisted of a dynamically vulcanized blend containing chlorobutyl rubber (figures 6 and 7). For this reason, work described further will focus on nylon 12 and vulcanized chlorobutyl rubber exclusively. Figure 6. Tensile strength of nylon/halogenated butyl rubber blends made with and without vulcanization

0

2

4

6

8

10

12

14

16

PA12

/BIIR

PA12

/BIIR

DV

PA12

/CIIR

PA12

/CIIR

DV

PA12

/IIR

PA12

/IIR

DV

Ult

ima

te T

en

sil

e S

tre

ng

th (

MP

a)

Figure 7. Elongation at break of nylon/halogenated butyl rubber blends made with and without vulcanization

0

50

100

150

200

250

300

350

400

PA12

/BIIR

PA12

/BIIR

DV

PA12

/CIIR

PA12

/CIIR

DV

PA12

/IIR

PA12

/IIR D

V

Elo

ng

ati

on

at

Bre

ak

(%

)

Very interesting data was obtained from testing of the swelling index in hexanes and CHCl3 of dynamically vulcanized blends containing variable ratios of nylon to rubber. Nylon 12 is insoluble in both of these solvents, while the rubber component of the blend is swollen. It was found that the swelling index in CHCl3 for the blends was significantly smaller than expected value, based on the proportion of the vulcanized rubber present (figure 8). This also indicates that the blends have significantly improved hydrocarbon resistance regardless of a large content of butyl rubber. It is unlikely that this phenomenon is related to different degrees of crosslinking. An explanation of this phenomenon can be found after looking once more

at the microscopic blend structure (figure 2b), where rubber particles can be seen coated by rigid, strong thermoplastic nylon resin. The nylon network most likely resists rubber expansion and further solvent diffusion. We can call it the “caging effect”. The “caging effect” seems to be highest around the expected phase reversal point with 15%-20% nylon, where blends elongation at break also reach a minimum value. This phenomenon may likely be used in designing other similar thermoplastic polymeric blend systems with improved chemical resistance. Figure 8. Swelling index and elongation at break for dynamically vulcanized blends in CHCl3

Mechanical Properties The mechanical properties of the blends were also peculiar. The results obtained were strongly dependent on the method of specimen preparation, and even the flow pattern in the same mold as can be seen in figures 9-13. Figure 9. Tensile strength and elongation at break of nylon/chlorobutyl rubber samples injection moulded, compression moulded, and extruded

0

5

10

15

20

25

30

35

40

45

50

Injection

Moulding

Compression Extrusion Injection

Moulding

Compression Extrusion

Ten

sile S

tren

gth

at

Bre

ak (

MP

a)

0

50

100

150

200

250

300

Elo

ng

ati

on

at

Bre

ak (

%)

Tensile Strength at Break (Mpa) Strain at Break (Video) (%)

PA12(L16)/CIIR1068 = 30/70 PA12(L16)/CIIR1068 = 40/60

Swelling Index & Elongation at Break for Dynamically

Vulcanized Blends

0

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80 90 100

% Polyamide

Sw

ellin

g In

dex

0

50

100

150

200

250

300

Elo

ng

ati

on

at

Bre

ak

Swelling Index

Elongation at Break

Figure 10. Modulus of elasticity of nylon/chlorobutyl rubber samples injection moulded, compression moulded, and extruded

0

50

100

150

200

250

300

350

400

450

Injection

Moulding


Moulding


Mo

du

lus

(M

pa

)

PA12(L16)/CIIR1068 = 30/70 PA12(L16)/CIIR1068 = 40/60

Figure 11 Hardness of nylon/chlorobutyl rubber samples injection moulded, compression moulded, and extruded

20

25

30

35

40

45

50

55

60

Injection

Moulding


Moulding


Sh

ore

D H

ard

ness

PA12(L16)/CIIR1068 = 30/70 PA12(L16)/CIIR1068 = 40/60

Figure 12. Comparison of tensile strength and elongation at break for injection moulded specimens “as moulded” and cut from impact bar

0

5

10

15

20

25

30

35

40

45

50

As Moulded cut from Impact Bar As Moulded cut from Impact Bar

Ten

sile S

tren

gth

at

Bre

ak (

MP

a)

0

50

100

150

200

250

300

Elo

ng

ati

on

at

Bre

ak (

%)

Tensile Strength at Break (Mpa) Strain at Break (Video) (%)

PA12(L16)/CIIR1068 = 30/70

PA12(L16)/CIIR1068 = 40/60

Figure 13. Comparison of modulus of elasticity for injection moulded specimens “as moulded” and cut from impact bar

0

5

10

15

20

25

30

As Moulded cut from Impact Bar As Moulded cut from Impact Bar

Mo

du

lus (

Mp

a)

PA12(L16)/CIIR1068 = 30/70 PA12(L16)/CIIR1068 = 40/60

With respect to tensile strength, the best result for PA/CIIR = 40/60 blends, 20.2MPa was obtained in the case of injection moulded specimens (ASTM D638M type 3), and the lowest value was for the compression moulded material (9.5 MPa). Extruded sheeting tested in the machine direction show intermediate results with 13.8 MPa. An identical trend was observed for PA/CIIR = 30/70 blends with the best tensile strength (14.3 MPa) also obtained for the injection moulded specimens. Compression moulded material show only approximately 50% tensile strength for injection moulded samples as is also recorded for 40/60 blends. Elongation at break also varied with the highest values (323%) obtained for extruded sheeting tested in the machine direction, and the lowest result (149%) for compression moulded samples of the 40/60 PA/CIIR blend. A reversed trend to elongation at break was observed for tensile modulus of the discussed blends. For example, the larger modulus value (180.1 MPa) and the larger durometer hardness (36 shore D) were recorded for injection moulded specimens with rubber to nylon ratio 30/70. Compression moulded samples of the same material showed modulus of 37.6 MPa and hardness Shore D under 30 Shore D. An experiment was conducted to confirm that the blend flow and structure orientation, and not the material thermal and shear history, during moulding of specimens were responsible for the variability in mechanical properties. Identical moulded and die cut specimens were taken from the same injection moulded sample (figure 14). The cavities of the mould for these specimens had different thermoplastic material flow patterns. Testing conducted for tensile strength, elongation at break, and tensile modulus showed an identical trend as observed earlier for specimens moulded using different techniques. For example, blend PA/CIIR = 30/70 had tensile strength for injection moulded specimens of 14.3 MPa vs. 7.4 MPa for specimens die cut from the neighbouring impact bar with less restricted flow within the cavity. Surprisingly, elongation at break was very similar for these two sets of specimens, in the range of 170%. Higher tensile strength was also associated with significantly higher tensile modulus, in the range of 180.0 MPa vs. 37.6 MPa respectively for the same tested specimens.

Figure 14. Specimens M3 (ASTM D638) injection moulded and cut from impact bar

This variability of mechanical properties is likely related, as was mentioned earlier, to blend microstructure and its orientation in the flow during moulding. An increase in material stress during flow seemed to cause increased orientation resulting in increased tensile strength and tensile modulus reflecting material stiffness. Warfare Agent Resistance Testing of injection moulded blend samples with different ratios of PA to CIIR, at a thickness of 1.5 mm, for resistance to warfare agents showed no signs of sulfur mustard gas penetration for 24h. Further evaluation of CW agent reemission (figure 15) showed a decrease from 38 um to 0 ug with an increase in nylon content from 15% to 40% when sulfur was used as a vulcanizing agent. A larger value of reemission was found for ZDEDC/ZnO vulcanization. This indicates that vulcanization of rubber and the type of vulcanizing agent seem to be an important factor in designing chemical resistant PA/CIIR blends. Regardless of the vulcanization method used, nylon chlorinated butyl rubber elastomeric blends show very low levels of reemission of warfare agents in comparison to other materials used recently for manufacturing protective equipment. Figure 15. Reemission of sulfur mustard from nylon/chlorobutyl blend It can be expected that, in the near future, developments in new special polymeric materials, an example of which is described in this paper as a nylon 12/chlorobutyl blend, will bring revolutionary changes to warfare agent resistant protective equipment with respect to decreased protection efficiency, a reduction of the burden on personnel, and a reduction in the manufacturing costs.

Injection moulded

Die cut

0

10

20

30

40

50

60

15 20 25 30 35 40 45

Nylon Content (Wt%)

Re-e

mis

sio

n (

µg

)

Sulfur

ZDEDC / ZnO

Conclusions

1. Nylon can be blended with butyl or halogenated butyl rubber to obtain material with thermoplastic elastomer properties

2. Properties of the blends depend on nylon/rubber ratio, mixing conditions, and vulcanizing agent used

3. Mechanical properties also depend on moulding conditions and mould geometry

4. Nylon-chlorobutyl blends show significantly better resistance to hydrocarbon and chlorinated

hydrocarbon solvents than can be expected from the rubber content in the blend

5. Nylon-chlorobutyl thermoplastic elastomers showed excellent resistance to penetration and reemission of warfare agents

UNCLASSIFIED SECURITY CLASSIFICATION OF FORM (highest classification of Title, Abstract, Keywords)

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1. ORIGINATOR (the name and address of the organization

preparing the document. Organizations for who the document

was prepared, e.g. Establishment sponsoring a contractor's

report, or tasking agency, are entered in Section 8.)

Polymer Engineering Company Inc. 110 – 3070 Norland Avenue Burnaby, BC V5B 3A6

2. SECURITY CLASSIFICATION

(overall security classification of the document, including special

warning terms if applicable)

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3. TITLE (the complete document title as indicated on the title page. Its classification should be indicated by the appropriate abbreviation

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The Preparation and Evaluation of Dynamically Vulcanized Thermoplastic Elastomeric Materials Based on Polyamide and Butyl Rubber Polymers

4. AUTHORS (Last name, first name, middle initial. If military, show rank, e.g. Doe, Maj. John E.)

Van Dyke, Jack D., Gnatowski, Marek

5. DATE OF PUBLICATION (month and year of publication of

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June 2008

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information, include Annexes,

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Contract Report

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13. ABSTRACT (a brief and factual summary of the document. It may also appear elsewhere in the body of the document itself. It is

highly desirable that the abstract of classified documents be unclassified. Each paragraph of the abstract shall begin with an indication

of the security classification of the information in the paragraph (unless the document itself is unclassified) represented as (S), (C) or

(U). It is not necessary to include here abstracts in both official languages unless the text is bilingual).

This report presents the results of blending experiments over a two year period on dynamically vulcanized polyamide / chlorobutyl blends. The objective was to prepare sufficient quantities of blends in the range of 30 – 40% Nylon by dynamic vulcanization, utilizing the optimum type and levels of vulcanization agents and process conditions, to allow a comparison of properties between injection molded, extruded (both machine and transverse direction), and compression molded specimens. Two curing systems were used – a sulphur and zinc oxide/ZDEDC system. In addition to mechanical properties the response to solvent attack (swelling index and % insolubles), resistance to penetration/re-emission of chemical warfare agents, as well as microscopy on selected samples were tested and compared under different methods of processing.

To ascertain the effect of orientation on mechanical properties an identical die was used for samples made by injection molding, compression molding, and extrusion. Type M3 specimens were cut from injection molded bars to allow a direct comparison of properties between molded and cut M3 specimens. The mechanical results indicate dramatic differences between specimens produced under various conditions, and there is a strong indication that orientation has a very large effect on the properties of the blends.

Initial work was also conducted on the modification and reinforcement of both phases of the blend (Nylon and butyl rubber) with nanoclay. Materials produced were evaluated for mechanical properties, flow characteristics, and response to solvent attack (swelling index and % insolubles). Microscopy was performed on selected samples.

TPE materials produced in this project have properties of interest for defence applications, including HD penetration, and may be used in clothing, boots and face ware applications.

Some of the results of this study contributed to a scientific paper published in the Journal of Applied

Polymer Science, Solvent Resistance and Mechanical Properties in Thermoplastic Elastomer

Blends Prepared by Dynamic Vulcanization, J. Appl. Polym. Sci. 109(3), 1535-1546, 2008. As well, selected results taken from this study (and other previous studies) were presented during the RAPRA Technology – Polymers in Defence and Aerospace Applications conference in Toulouse, France on September 19, 2007.

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Polyamide 12; chlorobutyl rubber; dynamic vulcanization; swelling index; microstructure; tensile strength; elongation at break; hardness; resistance to penetration; re-emission; Mustard gas; HD; 2,2’-dichloroethyl sulfide


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