10/2/12 Title: to modify choose 'View' then 'Heater and footer'

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CHANCES AND THREATS FOR NATURAL RUBBER

FOR USE IN LOW ROLLING RESISTANCE TYRES

Elastomer Technology and Engineering,

Enschede, the Netherlands

Malaysian Rubber Board

10/2/12 Wolff, Rubber Chem. Technol., 69 (1996) 2

Performance of Silica based NR Tires

50 40 30 20 10 0 phr

phr

Rolling resistance

Treadwear

Wet traction

NR Truck Tires

Carbon Black

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Tire Performance & Silica Technology

Polymer/Rubber type

Silica

Mixing technology

Coupling agent

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Silica-Silane-Rubber Coupling

Silanization: silica and silane reaction

Silanization: Primary & secondary

reaction

Vulcanization

Silane-rubber coupling

H3C

H

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Silica Reinforced Rubber Network

Silica-rubber coupling (silica-coupling agent-rubber bond)

Rubber–rubber bonds (sulphur crosslinks)

Silica

Rubber chain

x

Coupling agent: TESPT

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NR Research topics at UT/ETE

General aim Improving the reactivity of natural rubber (NR) towards silica

in order to make NR / HD silica more efficient for

reinforcement of tire-treads

Focus of the investigations   Optimization of the mixing process of NR-silica compounds

  Influence of proteins on silica reinforcement in NR

  Modification of NR to improve tire properties

  Different types of coupling agents more suited for NR

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Research questions

  Proteins versus silanes: (how) do they interfere?

  Rubber – filler: how do they interact

in a silica-filled NR compound?

  What is the influence of proteins on silica reinforcement in NR?

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Natural Rubber – A strategic green material

Advantages

  Renewable resource

  Converts solar energy to raw

material

  Effective CO2 sequester

  Low energy input

  Low fertilizer demand

  Valuable source of timber Source : Hevea Brasiliensis

Outstanding Properties

  Low hysteresis

  High tensile strength

  High elasticity

  Good resilience

  Low heat build up

  Resistance to abrasion

  Resistance to crack growth

  Flexibility at low temperature

cis -1,4 polyisoprene n

C

CH3

CH2 H2C

H C

Natural Rubber

48%

Synthetic Rubber

52 %

World rubber consumption, 2008

10/2/12 Tanaka et al., Rubber Chem. Technol, 67(1993),74(2001), 81(2008), 82(2009)

Sakdapipanich et al., Kautsch. Gummi Kunst. 3/2005, 10/2008 9

Network of Linear NR Chain (associated with proteins and phospholipids)

proteins Mono- or di- phosphate group

phospholipids

cis trans

C

CH3

CH2

H2C

H C

2 ω -terminal α-terminal

C

CH3

CH3 H2C

H C

n

C

CH3

CH2 H2C

H C C

CH3

CH2 CH2OH

H C ω-terminal

Mono- or di- phosphate group phospholipids

α -terminal (trans)2 (cis)n

H-bond or Mg2+

2 trans-1,4 isoprene units 1000 – 3000 cis-1,4 isoprene units

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Yeang et al., Methods 27 (2002)

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Proteins in Natural Rubber

Rubber phase

C-serum

Bottom fraction

(B-serum)

Protein distribution

25%

43%

32%

Rubber N2 content

Natural Rubber 0.3 – 0.6 %

Deproteinized

NR

0.08 – 0.12%

Skim rubber 1.5 – 2.5 %

Hevea latex : 30- 45% rubber hydrocarbon 3-5% non-rubber constituents water

Removal of non-rubber constituents: •  Enzymatic deproteinisation - protein •  Transesterification - phospolipids •  Saponification - protein + phospolipids

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Experimental: Compound Formulation

Ingredients phr

Natural Rubber, NR (varied) 100*

Silica, Ultrasil 7005 55

Silane, TESPT 5

Zinc Oxide 2.5

Stearic acid 1

Santoflex TMQ 2

TDAE oil 8

DPG 2

Sulphur 1.4

CBS 1.7 2nd stage mixing: two-roll mill

1st stage mixing in Brabender 350S Mixing conditions:

Mixing time: 14 minutes Rotor speed: 60 rpm Fill factor: 0.7 Dump temp. varied from 110°C till 170°C

Rubber types Nitrogen

content

( wt. % )

Protein

content

( wt. % )**

Deproteinized NR

(DPNR)

0.07 0.44

NR (SMR 20) 0.21 1.31

Skim Rubber* 2.06 12.88

**Conversion factor: 6.25

* Adjustment in Skim rubber formulation : 112 phr

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Processability: Mooney viscosity

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Rheological Properties

Time

Torq

ue

Flocculation

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Rheological Properties at 150oC

Filler-Filler Interaction: Payne Effect

Log strain

She

ar m

odul

us G

* Silica

Silica + silane

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Payne Effect versus Temperature

DPNR-no silane

NR-no silane

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Payne Effect versus Protein Content

0

0,1

0,2

0,3

0,4

0,5

0,1 1 10 100

Protein content in NR, wt %

G' at

0.56

% - G

' at 1

00%

, MPa

Silane

No silane

DPNR NR Skim Rubber

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Dispersion: Wolff Filler Structure Parameter

Wolff αf

DPNR

DPNR-no silane

NR-no silane NR

pmfm

f1ominDo

maxDminDmaxD

α=−−

−

Wolff, Kautsch. Gummi Kunst. 34, (1981)

SkimR- no silane

SkimR

Torq

ue

Temperature

0

10

20

30

40

50

60

70

80

90

100

110 120 130 140 150 160 170

Phys

ical

BRC

, %

Dump Temperature, °C

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Filler-Polymer Interaction: Bound Rubber Content

0

10

20

30

40

50

60

70

80

90

100

110 120 130 140 150 160 170

Che

mic

al B

RC

, %

Dump Temperature, °C

Silica compound NO SILANE

Chem.BRC (%)

Phys. BRC (%)

NR 0 57

DPNR 0 45

Skim R 0 51

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TEM Network Visualization (without silane)

NR-silica-no silane DPNR-silica-no silane

Silica

NR Network

Vacuole Vacuole

Silica

DPNR Network

Strong interface Weak interface Formation of vacuoles

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TEM Network Visualization (with silane)

NR-silica-silane DPNR-silica-silane

Silica

NR Network

No vacuoles

Silica

DPNR Network

Strong rubber to filler bonding

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AFM of silica vulcanizates

NR - no silane DPNR - no silane

1 x1μm

NR - silane DPNR - silane

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Tensile Properties

NR-no silane

DPNR- no silane

SkimR- no silane

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Reinforcing Index

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Dynamic Properties (Tan delta at 60°C)

0

0.05

0.1

0.15

0.2

100 120 140 160 180

Tan δ

at 6

0°C

Dump Temperature, °C

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Summary   Proteins coupling agent: antagonistic effect in silica reinforcement of NR

  Silane: enhances the properties of compound and vulcanizate in the

presence and absence of proteins

  Effect of proteins: most pronounced when no silane is used

  High amounts of proteins: disrupt the silica-silica network and improve silica

dispersion

  ….reduce the temperature sensitivity of the material

  …but do not improve final properties due to missing filler-polymer coupling

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Purification of NR

Tanaka et al., Rubber Chem. Technol, 82 (2009)

Removal of non-rubber constituents from NR • Enzymatic deproteinisation – protein • Transesterification - phospolipids • Saponification - protein + phospolipids

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Modification of NR

C CH

H2C

OO O

CH2 H2C

C CH

H3C

CH2 H2C

O

CH CH

H3C

CH2 H2C

CH2

CH3C C O CH3

O

Epoxidized Natural Rubber (ENR)

Maleated Natural Rubber (MNR) NR - methyl methacrylate graft copolymer

(NR-g-PMMA)

C CH

H3C

CH2 H2CNR

Modifications

grafting Graft copolymerization

Epoxidation

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Summary of Properties