Enhancing Filler-Rubber Compatability of Silica-Reinforced Tire Tread Compounds by using Chemicallt Modified Natural Rubbers

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Reinforced Tire Tread Compounds by using

p

y

g

Chemically Modified Natural Rubbers

K. Sahakaro

1

_{, K. Sengloyluan}

1,2

_{, P. Saramolee}

1

_{, W.K. Dierkes}

2

_,

J.W.M. Noordermeer

2

1

_{Department of Rubber Technology and Polymer Science, Faculty of Science and Technology,}

Prince of Songkla University, Pattani Campus, Thailand

2

_{Elastomer Technology and Engineering, Faculty of Engineering Technology,}

University of Twente, the Netherlands

1

(2)

Since 1967

Faculties @Pattani Campus

Science and Technology

gy

Education

Humanities and Social Science

Communication Science

Surat Thani

Communication Science

Fine and Applied Arts

Political Science

PSU

P tt

i

Phuket

Surat Thani

Pattani

College of Islamic Studies

Graduate School

2 Hat Yai

(3)

Since 1985

Department of Rubber Technology and Polymer Science

ff

B S (R bb

T h

l

)

Since 1985

offers B.Sc. (Rubber Technology)

M.Sc. (Polymer Technology)

Ph.D. (Polymer Technology)

(4)

Introduction

− Tire development

Introduction Tire development

www.asdreports.com A.Blume, F. Thibault-Starzyk. 2017. Rubber Fibres Plastics International 12(3), 152-157

Moving towards more “Green” tire industry

-

More energy-efficient and less CO

₂

emission tires

-

Use of safe compounding ingredients

-

Less dependence on petroleum-based raw materials, but more

4

(5)

Introduction

− Low rolling resistance tires

Introduction Low rolling resistance tires

The basis for low rolling resistance tire treads

g

Enhanced Filler-Elastomer Interactions

A.Blume. Reinforcement. In Elastomer Science and Engineering. University of Twente.

Double network (crosslinking &

coupling) reduces hysteresis,

i e less energy loss during dynamic

5 i.e. less energy loss during dynamic

(6)

Introduction

− Silica/silane technolgy

Introduction Silica/silane technolgy

Si O

O

H

Primary silanization reaction

Silica particle Si Si O O O O H S4 Si OC2H5 OC2H5 OC H Si (CH2)3 (CH2)3 OC2H5 H5C2O OC H +

Based on model compound study,

Si O H O OC2H5 OC2H5 1) Direct condensation 2) Hydrolysis of alkoxy group to form reactive hydroxyl group

• Only isolated and geminal

silanol groups react, and

approx. 25% of the Si-OH

Si O O O H OC H OC₂H₅ form reactive hydroxyl group prior to condensation reaction

groups react with silanes due

to the accessibility;

• Small molecules such as

+ EtOH Silica particle Si Si O O O O S₄ Si OC2H5 OC2H5 OC2H5 Si OC2H5 OC₂H₅ (CH2)3 (CH2)3

alcohols or amines can further

increase the hydrophobation of

the silica surface.

O H

Mixing dump temperature is the key parameter.

6

C. Hayichelaeh et al. Polymers10(6), 584; doi:10.3390/polym1006058

A.Blume, F. Thibault-Starzyk. 2017. Rubber Fibres Plastics International 12(3), 152-157

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I t d

ti

Alt

ti

Introduction − Alternatives

St t

i

t

h

fill

bb

i t

ti

9 Use of silane coupling agents

Strategies to enhance filler-rubber interactions

9 Silica surface modification,e.g. by plasma treatment, silane

pretreatment , admicellar polymerization, grafting of functional

groups

9 Use of polar rubber as compatibilizers

, e.g. CR, NBR, ENR

Natural rubber grafted with 3-octanoylthio-1-propyltriethoxysilane (NR-g-NXT)

Epoxidized natural rubber (ENR)

Epoxidized low molecular weight natural rubber (ELMWNR)

(8)

Preparation of NR-g-NXT

O C CH3 CH3 CH3 or CH3 S CH2 Si OCH2CH3 OCH2CH3 OCH2CH3 3 C H2C H3C O 6

Preparation of NR-g-NXT

Melt mixing

CH3 (I) (II) OCH2CH3 OCH CH O O _CH

Radical from initiator decomposition 3-Octanoylthio-1-propyltriethoxysilane (NXT)

Melt mixing

at 140

°C for 12 mins

Initiator:

1,1′-di(tert-b t l

) 3 3 5

S CH2 Si OCH2CH3 OCH2CH3 OCH2CH3 3 H3C H2C C O 6 C H2C H3C O 6 CH3 or O C CH3 CH3 CH₃

butylperoxy)-3,3,5-trimethylcyclohexane

(Luperox® 231XL40)

H2C C CH H3C CH2 n

NXT 10, 20 phr

Initiator 0.1 phr

H3C H3C CH O O O C CH₃ CH₃ CH₃ O C CH₃ CH₃ CH₃ CH₂ C CH2 CH₂ n C3H6 Si OCH2CH3 OCH2CH3 S H₂C C CH CH n OCH2CH3 S

NR-g-NXT

CH₃ CH₃ CH₃

8

3 6 Si OCH2CH3 OCH2CH3 Si OCH2CH3 OCH2CH3 C3H6

NR g NXT

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Characterization of NR-g-NXT

Virgin NR NXT 10 phr H2C C C H3C CH n Si OCH2CH3 OCH2CH3 S C3H6 Ha

g

m it ta n c e (a .u .) NXT 20 phr 3270 1125 NXT 20 phr Si OCH2CH3 OCH2CH3 C3H6 a b b Tr a n s 2908 2848 1670 1375 838 565 1010 1035 1075 1125 NXT 10 phr 400 800 1200 1600 2000 2400 2800 3200 3600 4000 Wave number (cm-1₎ 2956 2908 1467 ppm 0 1 2 3 4 5 6 7 8 9 Virgin NR Analysis results Amount of NXT (phr) virgin NR 10 20

R value from ATR-FTIR

R₁₀₇₅=A₁₀₇₅/A₁₃₇₅ 0.31 0.49 0.55 R₁₀₃₅=A₁₀₃₅/A₁₃₇₅ 0.22 0.42 0.49

Mol% of NXTfrom1_{H NMR} _0.00 _0.66 _1.32

Peaks at 1075 and 1035 cm-1 _{are assigned}

to Si-O-C and Si-OSi deformations.

9

Amount of grafted NXT (wt%) - 3.43 6.68 Amount of NXT used (wt%) - 9.09 16.67

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Effect of NR g NXT on silica filled NR compounds

1600 1800 kPa ) _(a) (b) 80 90

Effect of NR-g-NXT on silica-filled NR compounds

Zeosil 1165MP 55

1200 1400 1600 -G ′(1 00 % )] ( k None TESPT NXT NR-g-NXT 60 70 80 0 o C)

Zeosil 1165MP 55

TDAE 8

ZnO 3

Stearic acid 1

TMQ

1

600 800 1000 ct [ G ′(0 .5 6% ) 30 40 50 M L 1+ 4 ( 1 0 0 None

TMQ 1

DPG 1

CBS 1.5

Sulfur 1.5

0 200 400 P ayn e e ff ec 0 10 20 TESPT NXT NR-g-NXT 0 0 2 4 6 8 Silane contents (wt% rel. to silica) 0 0 2 4 6 8 Silane contents (wt% rel. to silica) mixing De‐mixing (fl l ti )

10 agglomerates

aggregates

(flocculation)

(11)

Effect of NR-g-NXT on silica-filled NR vulcanizates

(a) 10 12 a ) 25 30 a ) (a) 30 35 a ) (b)

(b)

(c)

(d)

6 8 o dul us ( M P a 15 20 tre n g th (MP a 15 20 25 tr e ngt h ( M P a

(a)

2 4 300% M o None TESPT NXT ₅ 10 Te ns ile s t None TESPT NXT ₅ 10 15 Tensi le s t None TESPT NXT 0 0 2 4 6 8 Silane contents (wt% rel to silica) NR-g-NXT 0 0 2 4 6 8 Silane contents NR-g-NXT 0 5 20 30 40 50 60

Chemically bound rubber

NR-g-NXT

(wt% rel. to silica) _{(wt% rel. to silica)} C e ca y bou d ubbe

contents (%)

(d)

₎

(c)

(a)

(b)

(a)

(b)

(c)

(d)

11 SEM micrographs of tensile fractured surfaces at 800x

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Effect of NR-g-NXT & sulfur compensation on the properties

Effect of NR g NXT & sulfur compensation on the properties

25 (b) 12 (a) 30 (a) 15 20 e ( d N .m ) ( ) 8 10 (MP a ) 20 25 (MP a ) 10 15 q ue di ff e re n c None 4 6 0 % M odul us 10 15 s ile st re n g th 0 5 Tor q TESPT NR-g-NXT NR-g-NXT+S 0 2 30 0 None TESPT NR-g-NXT NR-g-NXT+S 0 5 Te n s None TESPT NR-g-NXT NR-g-NXT+S 0 0 2 4 6 8 Silane contents (wt% rel. to silica) 0 0 2 4 6 8 Silane contents (wt% rel. to silica) 0 0 2 4 6 8 Silane contents (wt% rel. to silica)

Sulfur compensation for the system having NR-g-NXT by taking the compound

with TESPT as reference results in enhanced modulus and tensile strength.

12

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1.2 (b) 1.2 (b) 0.8 1.0 (b) 0.8 1 (b) 0.6 0.8

Ta

n

δ

0.6 0.8

Ta

n

δ

NR-g-NXT+S 0.2 0.4 _None TESPT 0.2 0.4 TESPT None 0.0 -80 -60 -40 -20 0 20 40 60 80 Temperature (o_C) NR-g-NXT 0 -80 -60 -40 -20 0 20 40 60 80 Temperature (o_C) NR-g-NXT

Compatibilizer types

T

g

(

o

_C)

Values of Tan δ

at 5

o

_C

_{at 60}

o

_C

Without

-47

0.09

0.11 TESPT

-45

0.10

0.07 NR g NXT

44 0 08

0 05

13 NR-g-NXT

-44

0.08

0.05 NR-g-NXT + sulfur

-42

0.08

0.06

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U

f ENR

ibili

Use of ENR as compatibilizer

Si OH Si O HO O H OH O H O H Si OH

14

K. Sengloyluan et al. 2014. European Polymer Journal. 51, 69-79.

(15)

U

f ENR

tibili

TESPT

lf

ti

35

Use of ENR as compatibilizer + TESPT + sulfur compensation

ENR-51 7.5 phr + TESPT

_{ENR-51 7.5 phr + TESPT+S}

25 30

M

Pa

)

15 20

s

tr

e

n

g

th

(

M

5 10

T

e

n

s

ile

s

ENR+TESPT ENR+TESPT+S TESPT 0 0 2 4 6 8

TESPT contents

None

(wt% rel. to silica)

TESPT 8.6 wt% rel.to silica

Without

With only half or smaller amount of TESPT is needed when ENR 51 is

15 With only half or smaller amount of TESPT is needed when ENR-51 is

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1.0 None TESPT

(b)

0.14 0.16 (a) 0 12 0.14 (b) 0 6 0.8 0.10 0.12 5 oC 0.08 0.10 0.12 6 0 o C 0.4 0.6

Ta

n

δ

ENR+TESPT+S None 0 04 0.06 0.08 Ta n δ at ENR+TESPT 0.04 0.06 0.08 Ta n δ at 6 ENR+TESPT 0.2 ENR ENR+TESPT ENR TESPT S 0.00 0.02 0.04 _ENR+TESPT+S TESPT None 0.00 0.02 ENR+TESPT+S TESPT None 0.0 -80 -60 -40 -20 0 20 40 60 80

Temperature (

o

_C)

TESPT 0 2 4 6 8 TESPT contents (wt% rel. to silica) 0 2 4 6 8 TESPT contents (wt% rel. to silica)

Temperature (

o

_C)

From the perspective of the “Magic Triangle of Tire Technology”, when the wet

skid resistance needs to be boosted e g for “Winter Tires” the combination of

16 skid resistance needs to be boosted, e.g. for Winter Tires , the combination of

ENR-51, TESPT and sulfur compensation presents itself as a better option.

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Use of ELMWNR as compatibilizer

600 700 a ) silica/TESPT non-compatibilizer LMWNR (a) 1 0 1.2 non-compatibilizer silica/TESPT 400 500 600 ul us , G ' ( M P a LMWNR ELMWNR-12 ELMWNR-28 ELMWNR-51 0.8 1.0 p ELMWNR-12 200 300 400 e sh ear m o d 0.4 0.6 Ta n δ 0 100 200 St o ra g e 0.2 ELMWNR-28 ELMWNR-51

ELMWNR

M

_w 0 0.1 1 10 100 1000 Strain (% ) 0.0 -100 -80 -60 -40 -20 0 20 40 60 80 100 Temperature (oC)

ELMWNR

M

_w

(mole% epoxide)

(g/mol)

0 65,000

12 55,000

28 49 000

With 10 phr of low molecular weight rubber

17

28 49,000

51*

N/A

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Use of ELMWNR as compatibilizer

ll

t f TESPT

+small amount of TESPT

120 140 No compatibilizer (b) 30 35 TESPT only 10 phr ELMWNR-28 + TESPT (c) 0.9 1.0 TESPT only 10 phr ELMWNR-28 + TESPT (b) 80 100 0 0 o C 20 25 30 th ( M P a ) no compatibilizer ELMWNR-28 0 6 0.7 0.8 )] M P a p tibili 60 80 M L (1 + 4 )1 0 TESPT 15 20 s ile s tr e n g t 0.4 0.5 0.6 G '( 0.56) -G '( 100 ) _{no compatibilizer} ELMWNR-28 20 40 ELMWNR-12 ELMWNR-28 5 10 Te n 0.1 0.2 0.3 [G

18

0 0 5 10 15 20

Low MW rubber content (phr)

00 0 0.0 1.5 3.0 4.5 TESPT content (phr) 0.0 0.0 1.5 3.0 4.5 TESPT content (phr)

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Conclusions

NR-g-NXT, ENR and ELMWNR show their potential to be used

tibili

f

ili

i f

d

bb

d

Conclusions

as compatibilizers for silica-reinforced rubber compounds as

observed by the improved processability and enhanced

mechanical & dynamic properties compared to the system

without compatibilizer.

The use of state-of-the-art TESPT at its optimum loading

remains superior but the application of these modified rubbers

with a small amount of TESPT and sulfur compensation results

in properties that close to the levels obtained with TESPT.

NR-based compatibilizer/TESPT combinations provide

environmental benefits from the use of renewable

material and a reduced amount of ethanol emitted from

TESPT silane coupling agent during processing.

19

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Acknowledgement

Department of Rubber Technology and Polymer Science

p

gy

y

Prince of Songkla University, Pattani Campus, Thailand

Department of Elastomer Technology and Engineering

University of Twente, Enschede, the Netherlands

Rubber Stichting

(The Dutch Natural Rubber Foundation)

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