toughening modification of poly(vinyl chloride)/ α-methylstyrene-acrylonitrile-butadiene-styrene...

Toughening Modification of Poly(vinyl chloride)/a-Methylstyrene-Acrylonitrile-Butadiene-StyreneCopolymer Blends via Adding Chlorinated Polyethylene

Zhen Zhang, Jun Zhang, Hongyong LiuDepartment of Polymer Science and Engineering, College of Materials Science and Engineering, NanjingUniversity of Technology, Nanjing 210009, China

In this study, poly (vinyl chloride) (PVC)/a-methylstyr-ene-acrylonitrile-butadiene-styrene copolymer (AMS-ABS) (70/30)/chlorinated polyethylene (CPE) ternaryblends was prepared. With the addition of CPE, it didnot exert a negative influence in both the glass transi-tion temperature and heat distortion temperature.Thermogravimetric analysis showed that addition ofCPE did not play a negative role in the thermal stability.With regard to mechanical properties, high toughnesswas observed combined with the decrease in tensilestrength and flexural strength. With the addition of 15phr CPE, the impact strength increased by about 21.0times and 8.5 times in comparison with pure PVC andPVC/AMS-ABS (70/30) blends, respectively. The mor-phology correlated well with the impact strength. Itwas also suggested from the morphology that shearyielding was the major toughening mechanisms for theternary blends. And there existed a change in the fibrilstructures that are observed in scanning electronmicrophotographs. Our present study shows that com-bination of AMS-ABS and CPE improves the toughnesswithout sacrificing the heat resistance, and the valueof notched impact strength can be enhanced to thesame level of super-tough nylon. POLYM. ENG. SCI.,54:378–385, 2014. ª 2013 Society of Plastics Engineers

INTRODUCTION

Nowadays poly (vinyl chloride) (PVC) has already

been widely used in the form of pipes, sheets, cables,

wood composites, etc [1–7]. However, for rigid PVC, its

low heat distortion temperature (HDT) has restricted its

wider use especially in some harsh environment and con-

ditions. A very effective way to solve this deficiency is

via adding a polymer that both exhibits a higher glass

transition temperature (Tg) and is compatible with PVC

[8]. Based on this discipline, a-methylstyrene/styrene/

acrylonitrile copolymer [9], a-methylstyrene/acrylonitrile

copolymer (a-MSAN) [10–13], chlorinated PVC [14, 15],

imide polymers [16, 17] and styrene/maleic anhydride co-

polymer [18, 19] have already been reported. Unfortu-

nately, incorporation of these polymers inevitably contrib-

utes to the loss in fracture toughness, albeit they can

enhance the HDT of PVC.

Despite the aforementioned drawback, rigid PVC is

very sensitive to the notch and its notched impact strength

is very low especially at low temperature. To overcome

this disadvantage, several toughening modifier such as

chlorinated polyethylene (CPE), acrylic resin (ACR),

methyl methacrylate-butadiene-styrene copolymer (MBS),

nitrile butadiene rubber (NBR) and ethylene-vinyl acetate

copolymer (EVA) have been introduced and widely

reported [2]. But none of these polymers play a positive

role in the HDT of PVC, and high dosage of these modi-

fiers even result in a reduction in HDT [2, 20]. Thus, it is

very meaningful and necessary to overcome these two

deficiencies of rigid PVC simultaneously.

To solve these problems at the same time, both

a-methylstyrene/acrylonitrile copolymer and toughening

modifiers (CPE and ACR) are introduced in our previous

work to produce a ternary blends that is combined with

high toughness and high HDT [21, 22]. a-MSAN has a

higher glass transition temperature compared with that of

pure PVC [10–13], and its miscibility window between

PVC and a-MSAN is very narrow [23], indicating that

addition of a-MSAN could improve the HDT of PVC but

embrittle rigid PVC. Either incorporation of CPE or ACR

into PVC/a-MSAN binary blends could increase the

toughness [21, 22], and ACR exhibits a higher toughening

efficiency [22].

In this article, PVC blends with largely improved

toughness have been successfully prepared via blending

PVC, a-methylstyrene-acrylonitrile-butadiene-styrene co-

polymer (AMS-ABS) and CPE together. AMS-ABS is the

product of modified a-MSAN. Like a-MSAN, it is com-

patible with PVC and has a higher HDT than PVC [24].

Moreover, the polybutadiene rubber that is integrated

Correspondence to: Jun Zhang; e-mail: [email protected]

Contract grant sponsor: Scientific Achievement Transformation Founda-

tion of Jiangsu Province; contract grant number: BA2010017; contract

grant sponsor: Priority Academic Program Development of Jiangsu

Higher Education Institutions.

DOI 10.1002/pen.23568

Published online in Wiley Online Library (wileyonlinelibrary.com).

VVC 2013 Society of Plastics Engineers

POLYMER ENGINEERING AND SCIENCE—-2014

with a-methylstyrene-acrylonitrile-styrene matrix could

improve the toughness of PVC to some extent, which is

justified by our previous paper [25]. On the other hand,

CPE has a long reputation to act as an impact modifier

for PVC [20]. CPE with 36 wt% chlorine is immiscible

with PVC [26] and could provide PVC with excellent

impact strength and processability [27–29]. Although no

literatures about AMS-ABS/CPE blends has been

reported, Hwang and Kim [30] reported that the impact

strength of styrene-acrylonitrile copolymer (SAN) was

dramatically increased with the introduction of CPE and

the brittle-ductile transition (BDT) was observed at the

composition of 30–40 wt% CPE. Thus, it is logical to

incorporate CPE in PVC/AMS-ABS binary blends for fur-

ther toughening.

To characterize the structure and properties of the

blends, the effect of CPE on the Tg, HDT and thermal sta-

bility of PVC/AMS-ABS (70/30) blends was investigated.

When it comes to the mechanical properties, both toughness

and strength were determined. The toughening mechanism

was also proposed based on the results of morphology.

EXPERIMENTAL

Materials and Sample Preparation

PVC used in this study was a suspension grade resin

(S-1000) provided by Sinopec Qilu, China with a K value

of 66. The AMS-ABS copolymer, with the commercial

name of BLENDEX 703 and 14 wt% of butadiene, was

supplied by Chemtura, America. CPE (135A), with

36 wt% of chlorine, was produced by Weifang Yaxing

Chemical. Other additives, such as organotin, calcium ste-

arate and polyethylene wax were all industrial grade and

utilized as stabilizer, metal and PVC surface lubricant and

slip lubricant, respectively.

PVC 70 phr, AMS-ABS 30 phr, organotin 1.5 phr, cal-

cium stearate 1 phr and polyethylene wax 0.8 phr were

premixed in a high-speed mixer at 858C for 10 min to

obtain the PVC compound. The obtained PVC/AMS-ABS

(70/30) compound and CPE were melt mixed with a two-

roll mill at 1808C for 10 min, followed by molding into

the sheets with the thickness of 2 and 4 mm by compres-

sion-molding at 1808C. The content of CPE was varied,

and the blend ratios of PVC/AMS-ABS/CPE ternary

blends were based on the mass fraction of polymers (70/

30/0, 70/30/3, 70/30/5, 70/30/10, 70/30/12, 70/30/15, and

70/30/20).

Glass Transition Temperature

The glass transition temperature values were deter-

mined by using a differential scanning calorimeter (Q200,

TA). Each sample that is about 10 mg was first scanned

from room temperature to 1808C at a heating rate of

408C min21, then quickly followed by being quenched to

08C at a heating rate of 408C min21 and scanned for the

second time to 1808C at a heating rate of 108C min21.

The glass transition temperature was defined as the mid-

point of the transition.

Heat Distortion Temperature

To determine the heat distortion temperature, Vicat/

HDT equipment (ZWK1302-2, Shenzhen SANS Testing

Machine, China) was used. The development of the tests

were conducted at a heating rate of 1208C h21 under the

maximum bending stress of 1.80 and 0.45 MPa, respec-

tively, following ISO 75-1.

Thermogravimetric Analysis

Thermogravimetric analysis (TGA) was carried out by

using a TGA (Pyris 1, Perkin-Elmer, USA) in a nitrogen

flow (20 ml min21). Each scan was conducted from 50 to

6008C with a heating rate of 208C min21.

Mechanical Properties

Tensile tests and flexural tests were carried out by a

universal testing machine (CMT 5254, Shenzhen SANS

Testing Machine, China) according to ISO 527 and ISO

178 with a speed of 5 and 2 mm min21, respectively. To

investigate the influence of CPE on the notch sensitivity of

the blends, different notch depth including 2.0, 3.0, 4.0,

5.0, 5.5, and 6.0 mm were introduced in each blends. The

notched Izod impact strength of specimens with different

notch depth was determined by an impact tester (UJ-4,

Chengde Machine Factory, China), following ISO 180.

Morphology

Scanning electron microscopy (JSM-5900, JEOL,

Japan) was used to observe the impact-fractured surfaces

of the blends with an accelerating voltage of 15 kV. The

chosen specimens were with a notch depth of 2.0 mm.

The impact-fractured surfaces were coated with gold

before viewing and the observed location was laid in the

central regions of the surfaces. Neither staining nor any

other chemical treatments were used in this study.

RESULT AND DISCUSSION

Glass Transition Temperature

Differential scanning calorimetry (DSC) curves of pure

PVC and different blends are presented in Fig. 1. Pure

PVC/AMS-ABS (70/30) blends exhibit a single Tg of

88.88C, the value of which is higher than that of pure

PVC (80.58C) but lower than that of pure AMS-ABS

(120.08C). This feature indicates that PVC is miscible

with the a-methylstyrene/acrylonitrile-styrene component

DOI 10.1002/pen POLYMER ENGINEERING AND SCIENCE—-2014 379

in AMS-ABS. With regard to the chlorinated polyethyl-

ene, the glass transition behaviors are not exhibited due to

the lack of low-temperature condition in DSC tests. How-

ever, it is expected to be 221.28C for CPE with 36% of

chlorine following the below equation [31]:

Tgð�CÞ ¼ 0:09x2 � 4:64xþ 29:19 (1)

where x is the content of chlorine. With the incorporation

of CPE into PVC/AMS-ABS (70/30) binary blends, one

can see that no obvious changes occur in the glass transi-

tion behaviors, and the ternary blends still exhibit a single

Tg. This feature at least suggests that incorporation of

CPE does not play a negative role in the compatibility

between PVC and AMS-ABS.

In addition, as shown in Table 1, the Tg almost

remains constant with different blends and no significant

shifts to lower temperature are observed even with the

introduction of CPE. For AMS-ABS, the Tg of polybuta-

diene is 2808C [32]. On the basis of this fact, we can

conclude that both CPE and the PB component in AMS-

ABS can be dispersed in the PVC/AMS-ABS matrix. In

other words, a dual-phase structure with PVC/AMS-ABS

as the continuous phase while CPE and polybutadiene

component as the dispersed phase would be expected in

the ternary blends system.

Heat Distortion Temperature

HDT is used to evaluate the heat resistance of different

blends, and the curves are listed in Fig. 2. As shown in

Fig. 2, HDT of PVC/AMS-ABS (70/30) binary blends in

this work is 85.68C, which is higher than that of pure

PVC [22], indicating that incorporation of AMS-ABS

could improve the heat resistance of PVC. With regard to

the ternary blends, HDT almost remains constant and only

a slight decrease in HDT is observed at high level of

CPE. For amorphous polymers, the higher the Tg is, the

higher HDT can be obtained [8]. Because the Tg of differ-

ent blends almost do not vary with different compositions,

the results of HDT are consistent with the results of DSC.

Thermal Stability

Dynamic thermogravimetric and the derivative thermog-

ravimetric (DTG) curves are shown in Fig. 3. For pure

PVC/AMS-ABS (70/30) binary blends, the thermal degra-

dation consists of three basic degradation steps. Like the

behavior of the binary blends, the ternary blends also ex-

hibit three degradation steps. The first degradation step,

which is at the temperature up to about 3698C, presents the

process of dehydrochlorination and the formation of poly-

enes caused by PVC and CPE [33]. The second and the

third step occur in the temperature range of 369–4448C and

444–5008C, respectively. The former is corresponded to the

degradation of AMS-ABS and the latter is attributed to the

elimination of low molecular weight hydrocarbons from the

polyenes residue [34]. In addition, as seen in the DTG

FIG. 1. Effect of chlorinated polyethylene content on the glass transi-

tion behavior of PVC/AMS-ABS (70/30) binary blends (‘‘Blends’’ in

this figure represents PVC/AMS-ABS (70/30) binary blends). [Color

figure can be viewed in the online issue, which is available at

wileyonlinelibrary.com.]

TABLE 1. Glass transition temperature of pure PVC and different

blends.

CPE content (phr)

Tg (8C)

PVC PVC/AMS-ABS (70/30) matrix

0 80.5 88.8

3 — 88.7

5 — 91.8

10 — 92.1

12 — 91.6

15 — 92.7

20 — 92.7

FIG. 2. Effect of chlorinated polyethylene content on the heat distor-

tion temperature of PVC/AMS-ABS (70/30) binary blends. [Color



380 POLYMER ENGINEERING AND SCIENCE—-2014 DOI 10.1002/pen

curves, the temperature at the first peak is shifted to higher

values combined with lower maximal rate of degradation

(height of the peak) as the content of CPE increases. This

indicates that the degradation state of binary blends can

slightly decrease with the introduction of CPE in the first

degradation step. Interestingly, no obvious changes in the

second peak of the DTG curve are observed. Because the

degradation of AMS-ABS mainly occurs in the second

degradation step, it can be concluded that the interaction

between CPE and a-MSAN is weak [22]. With regard to

the third step of degradation, the maximal rate increases as

the content of CPE increases.

The detailed results obtained from the curves of TG

and DTG of different blends are summarized in Table 2.

The Tonset increase from 285 to 2888C with the introduc-

tion of 15 phr CPE, though the effect of CPE in Tonset

can be ignored when the content of CPE is 5 phr. Similar

results can be gained when it comes to the T10%. How-

ever, the introduction of CPE increases T50% effectively.

All these results indicate that CPE does not play a nega-

tive role in the stability of PVC/AMS-ABS binary blends.

These results are expected, since CPE exhibits a higher

thermal stability than PVC. Similar to PVC, the dehydro-

chlorination is also the dominant reaction in the CPE deg-

radation [34, 35]. However, PVC exhibits a fast zipper

dehydrochlorination, while the dehydrochlorination of

CPE is a slow elimination of random chlorine and occurs

at a relatively higher temperature [33, 34]. The chlorine

radical that is formed from the scission of PVC could

diffuse into the CPE phase for reinitiation of the dehydro-

chlorination of CPE, and thus the rate of dehydrochlorina-

tion decreases. With regards to the weight loss, increasing

the content of CPE decreases the weight loss of the first

degradation step but increases that of the third degrada-

tion step. This change could be explained by the dilution

effect caused by the introduction of CPE. In sum, incor-

poration of CPE does not play a negative role in the ther-

mal stability of PVC/ AMS-ABS (70/30) blends.

Mechanical Properties

As shown in Fig. 4, incorporation of CPE can drasti-

cally improve the toughness of PVC/AMS-ABS (70/30)

blends. We first take the impact strength of the specimens

with 2-mm depth as examples. Pure PVC/AMS-ABS (70/

30) blends exhibits a relatively lower toughness with an

impact strength of 12.9 kJ m22. A BDT is found to occur

in the range of 5–15 phr CPE, in which the impact

strength increases from 23.3 to 110.0 kJ m22, indicating

that the introduction of CPE could give the blends system

with appreciable increase in toughness. With further addi-

tion of CPE, the influence of CPE on the increase in

impact strength becomes less. The impact strength of

specimens with 2-mm depth is enhanced by about 21.0

times and 8.5 times in comparison with pure PVC (5.0 kJ

m22) [12] and PVC/AMS-ABS (70/30) blends, respec-

tively, when the dosage of CPE is 15 phr. On the other

hand, the maximum value of the impact strength in the

ternary blends is at the same level of super-tough nylon

[36–38]. However, for PVC/CPE binary blends, it is

reported that more than 20 phr CPE are required to

FIG. 3. TG and DTG curves for PVC/AMS-ABS/CPE (70/30/varible)

blends. [Color figure can be viewed in the online issue, which is avail-

able at wileyonlinelibrary.com.]

FIG. 4. Notched impact strength of PVC/AMS-ABS/CPE (70/30/vari-

able) blends with different notch depth; the black arrow indicates the

increasing notch depth. [Color figure can be viewed in the online issue,

which is available at wileyonlinelibrary.com.]

TABLE 2. TG analysis results of PVC/AMS-ABS/CPE

(70/30/varible) blends.

CPE content

(phr)

Tonseta

(8C)

T10%a

(8C)

T50%a

(8C)

Weight loss (%)

Step 1 Step 2 Step 3

0 285 298 358 52.2 22.7 14.05 284 299 368 50.2 22.4 17.0

15 288 303 376 48.3 22.0 19.4

a Tonset%, T10% and T50% are the temperature corresponding to 5, 10,

50 wt % of weight loss respectively.


enhance impact strength to about 80.0 kJ m22 [39, 40],

while addition of 15 phr CPE [21, 41] only contributes to

a 4.0 times increase in impact strength of PVC/a-MSAN

(70/30) blends. Both of the above two mentioned binary

blends systems exhibit lower impact strength compared

with the ternary blends system in this article. And one of

the obvious differences between AMS-ABS and a-MSAN

is the existence of polybutadiene component. Thus, we

can conclude that the polybutadiene component might be

responsible for such a drastic increase in toughness, and a

synergistic toughening effect is achieved by the combina-

tion of CPE and polybutadiene component. The toughen-

ing mechanism will be discussed in the next section.

It is well-known that rigid PVC is sensitive to the

notch depth [2, 20], and via adding elastomers this defi-

ciency can be overcome. Thus, we investigate the influ-

ence of CPE on the notch sensitivity of PVC/AMS-ABS

blends. As can be seen in Fig. 4, the impact strength of

different blends exhibits the same BDT, even though the

notch depth is varied. To better understand the influence

of notch depth on the impact strength, the retention rate

of impact strength of different notch depth is shown in

Table 3. As the content of CPE increases, the retention

rate of impact strength exhibits an increasing trend, when

the notch depth is relatively low. For example, with the

addition of 15 phr CPE, the retention rate of impact

strength of specimens with 3-mm notch depth increases

from 67.4% for pure PVC/AMS-ABS (70/30) blends to

87.4%. This indicates that incorporation of CPE could be

helpful to increase the resistance to notch sensitivity.

However, as the notch depth continues to increase, the

improvement in the retention rate becomes less. Anyway,

the impact strength of blends containing CPE is still con-

siderably higher than that of pure PVC/AMS-ABS (70/30)

blends with the same notch depth.

With regard to the elongation at break, pure PVC/

AMS-ABS (70/30) blends exhibits an elongation at break

of 114%. With the incorporation of 15 phr CPE, the elon-

gation at break increases to 187 %. Thus, addition of CPE

could improve the tensile ductility of PVC/AMS-ABS

(70/30) blends significantly.

Although drastic improvement in toughness and ductil-

ity are observed, the loss in the strength and modulus is

accompanied as shown in Figs. 5 and 6. With the addition

of 15 phr CPE, the tensile strength, flexural strength and

flexural modulus are 38.7, 50.5, and 1670 MPa compared

with 50.7, 73.8, and 2413 MPa for PVC/AMS-ABS (70/

30) binary blends. And further addition of CPE contrib-

utes to a continuous decrease. This decrease is owing to

the lower strength and modulus of CPE [42]. It is worthy

noting that both tensile and flexural properties are almost

the same and still remain at a high level, when the con-

tent of CPE is less than 5 phr. This is in agreement with

the BDT of impact strength.

Morphology

SEM is used to observe the impact-fracture surface of

different blends and the SEM micrographs are shown in

Fig. 7. Some voids are observed for PVC/AMS-ABS bi-

nary blends and PVC/AMS-ABS/CPE ternary blends,

indicating a dual-phase structure that is actually a neces-

sary condition for rubber toughened plastic [43, 44].

These voids are resulted due to the debonding of rubbers

particles, which is consistent with the results of DSC that

both the CPE component and polybutadiene component

are not miscible with the matrix.

The surfaces of the fractured pure PVC/AMS-ABS

blends is relatively flat (see Fig. 7A), and only slight do-

main distortions are observed, thus indicating that the

impact strength of PVC/AMS-ABS blends is not high.

This is an expected result, since in this situation the matrix

mainly bear the stress and the toughening effect contrib-

uted by the polyethylene component is very limited,

although the debonding of rubber particles could absorb a

considerable amount of energy [44]. As the CPE content

increase to 5 phr (see Fig. 7B), the surface becomes rela-

tively rough, and some pseudo-fibril structures are

observed. This reveals that the impact strength is

TABLE 3. Retention rate of impact strength with different notch depth (%).

CPE content (phr)

Retention ratea (%)

3.0 mm 4.0 mm 5.0 mm 5.5 mm 6.0 mm

0 67.4 55.8 50.4 36.7 34.2

3 69.8 59.5 53.8 49.8 49.7

5 75.1 56.3 52.0 43.8 43.7

10 81.6 53.7 38.5 39.0 34.0

12 83.8 59.0 42.7 40.6 32.0

15 87.4 63.3 45.0 32.0 28.0

20 86.9 60.9 43.4 34.8 33.5

a The retention rate is defined as the percentage of impact strength

for the blends with a certain notch depth compared with the impact

strength of that blends with a 2-mm notch depth.

FIG. 5. Effect of chlorinated polyethylene content on the tensile prop-

erties of PVC/AMS-ABS (70/30) binary blends. [Color figure can be

viewed in the online issue, which is available at wileyonlinelibrary.com.]


enhanced. The images of pure PVC/AMS-ABS blends and

ternary blends (see Fig. 8) with 5 phr CPE clearly support

the toughening effect, since some stress whitening area

can be observed for ternary blends containing 5 phr CPE.

With further addition of CPE, it can be seen in Fig. 8

that the ternary blends experienced partial breakage under

the impact loading. The stress whitening area exhibit a

semi-crescent shape, and its area increases until the dos-

age of CPE is 15 phr, which is consistent with the results

of impact strength [2]. The SEM micrograph of the ter-

nary blends containing 10 phr CPE (see Fig. 7C) exhibits

a very interesting morphology. Besides the voiding at the

interface, the pseudo-fibril has successfully transformed

into the fibril with a very short length. In addition, these

fibrils with relatively short length act as the path arresters

during the impact loading, and thus enhanced the impact

toughness [45]. As the CPE content increases to 15 phr,

the observed surface (see Fig. 7D) is completely deformed

and shows extensive drawing of the matrix. The length of

fibrils becomes longer, hence its capacity to bridge and

retard the propagation of the crack also increase [39].

Toughening Mechanism

Based on the above facts, the toughening mechanism

can be summarized as below. The existence of polybuta-

diene particles in AMS-ABS could not be sufficient to

promote the shear yielding of the whole matrix, which is

mainly due to the insufficient dosage. In other words, the

polybutadiene particles are isolated, and the stress field

around one certain particle is seldom affected by its

neighboring one. The observed fibrils in the ternary

blends indicate shear yielding is the main mechanism.

According to Wu’s theory [46–50], for rubber toughened

plastics, the BDT usually occurs at a critical surface-to-

surface interparticle distance or the critical matrix–liga-

ment thickness [47].

tc ¼ dc½ðp=6UrÞ1=3 � 1� (2)

where tc is the critical matrix–ligament thickness, dc is

the critical rubber particle diameter, Fr is the rubber vol-

ume fraction, t is the average surface-to-surface interpar-

ticle distance, and is strongly depended upon the rubber

volume fraction. For a given polymer/rubber blends sys-

tem, if t . tc, the matrix yielding could not be pervade

FIG. 6. Effect of chlorinated polyethylene content on the flexural prop-

erties of PVC/AMS-ABS (70/30) binary blends. [Color figure can be

viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIG. 7. Effect of CPE content on the morphology of PVC/AMS-ABS (70/30) blends: (A) 0 phr; (B) 5 phr;

(C) 10 phr; (D) 15 phr.


over the entire matrix. In contrast, if t , tc, the shear

yielding can be drawn in the whole matrix and the blends

will be tough. In this system, incorporation of CPE could

be inserted into the places between different polybuta-

diene particles. Because CPE particles themselves can be

dispersed in the matrix, this is very beneficial and actually

reduces surface-to-surface interparticle distance. The

stress field between different rubber particles (both poly-

butadiene particles and CPE particles) begins to overlap,

and once the continuum percolation of the stress volume

around the rubber particles are accomplished, the BDT in

impact strength will be achieved simultaneously. The

observed increase in the length of fibrils also corroborates

this assumption. As the CPE content further increases

(higher than 15 phr CPE), the stress field has already been

saturated, so its positive role in the toughness becomes

less. However, the proposed toughening mechanism is

still required to be substantiated by the transmission elec-

tron microscope (TEM) study. On the basis of the SEM

micrographs, we are not able to distinguish either polyeth-

ylene phase or CPE phase, and there is a lack of informa-

tion about whether these two components interact with

each other.

CONCLUSION

PVC/AMS-ABS/CPE with largely improved toughness

ternary blends has been prepared via melt blending. Addi-

tion of CPE exerts little influence on the HDT and

thermal stability of the blends. The glass transition tem-

perature almost remains unchanged over all composition,

indicating CPE is immiscible with PVC/AMS-ABS

matrix. With regard to mechanical properties, super-tough

behavior has been observed for blends containing 15 phr

CPE. Addition of 15 phr CPE results in an increase in

impact strength by about 21.0 times and 8.5 times in

comparison with that of pure PVC (5.0 kJ m22) and that

of PVC/AMS-ABS (70/30) blends, respectively. The

value of the impact strength is even close to the super-

tough nylon. In addition, incorporation of CPE decreases

tensile strength and flexural properties. Both fibrils and

voids are observed in the fractured surface of the ternary

blends, and the length fibrils increase with the increasing

amount of CPE. Based on the morphology, it is suggested

that shear yielding is the main toughening mechanisms,

and the improvement in toughness can be well-explained

by Wu’s model. So far, there exists a limitation of this

work, that is, the existence of polybutadiene is prone to

cause ultraviolet irradiation degradation and thermal oxy-

gen degradation resulting in the destruction of polymer

chains. Ultraviolet absorbent or titanium pigment should

be added so that the weatherability of the blends can be

enhanced. That work is being carried out and will be per-

formed in our future work.

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