M. Tiwari, R. N. Datta, A. G. Talma, J. W. M. Noordermeer, W. K. Dierkes

Department of Elastomer Technology and Engineering,

University of Twente, 7500 AE Enschede, The Netherlands

W. J. van Ooij

Department of Chemical and Materials Engineering,

University of Cincinnati, Cincinnati, OH 45221-0012, USA

Plasma polymerization of Acetylene and Thiophene onto

Silica - an Alternative to Improve Reinforcement of Silica

in S-SBR and EPDM

ETE – VKRT MeetingUniversity of Twente, Enschede

December 12, 2008

2

Contents

ð Introduction

ð Aim

ð Experimental

ð Results & discussion

ð Summary

ð Acknowledgement

3

Filler reinforcement

Filler dispersion depends onPolymer:

ð Type

ð Molecular weight

Filler:

ð Particle size distribution

ð Structureð Surface activity

Introduction

è Non-uniform dispersion influences the properties

4

Plasma Polymerization

Monomer Plasma-Polymer - highly crosslinked- disordered structure- two-dimensional network- thermally, chemically stable- very adherent- bulk properties preserved

Introduction

5

Plasma reactorIntroduction

- RF (13.56MHz) plasma: very stable and reactive

- Tumbler reactor: 350 g capacity

CarrierGas 1

RF Coils

Flange

Monomer 2Vacuum Pump

Thick Pyrex

MotorVacuumGrease

PressureGauge

RF Source13.56MHz

AC

Probe 1 Probe 3

Plate

Baffles Oil Trap

40cm

20cm

20cm

Throttling Valve

Carrier Gas 2

O-ring

or monomer 1

Probe 2

6

Aim of the work

_ Comparison of the effect of Plasma-thiophene and –acetylene coated silica in terms of their:

…achieved by surface modification by plasma polymerization process

- compatibility

- wettability

- dispersion

with S-SBR and EPDM

7

Polymers: - S-SBR (Buna® VSL 5025-0 HM, Lanxess GmbH):

25 wt% styrene, 75 wt% butadiene

- EPDM (Keltan® 4703, DSM Elastomers B.V.):

9 wt% ethylidene norbornene, 48 wt% ethylene, 43 wt% propylene

Fillers: - Precipitated silica (Ultrasil VN3, Degussa GmbH)

Plasma monomer: -High purity acetylene (C2H2, Wright Brothers, Inc.)

-High purity thiophene (C4H5S, Sigma-Aldrich, Inc.)

Silica coupling agent: Bis-(triethoxysilylpropyl) tetrasulphide, TESPT (Si69, Degussa GmbH)

MaterialsExperimental

8

ExperimentalPlasma polymerization

Monomers: - Acetylene- Thiophene

9053100PA-Silica

9020100PTh-Silica

Time (minutes)

Monomer Pressure

(Pa)

Power(W)

Code

9

ð Thermo-Gravimetric Analysis

(TGA7, Perkin-Elmer; rate of heating 10°C/min.)

ð Time-of-Flight Secondary Ion Mass Spectrometry (ToF- SIMS)

ExperimentalFiller characterization

ðWater penetration measurements

10

ExperimentalCompounding

U: Untreated; PA: Plasma acetylene coated; PTh: Plasma thiophene coated; T: Silanised with TESPT

S: S-SBR; E: EPDM

1.51.51.51.5--------ZBEC

0.80.80.80.8--------TMTD

--------1.51.51.51.5DPG

1.51.51.51.51.51.51.51.5CBS

1.041.51.51.51.041.51.51.5Sulfur

4------4------Silane (TESPT)

2.02.02.02.02.52.52.52.5Stearic acid

55552.52.52.52.5ZnO

5050505050505050Silica

100100100100--------EPDM

--------100100100100S-SBR

phrphrphrphrphrphrphrphr

ETEPThEPAEUSTSPThSPASU

SamplesComponents

11ExperimentalMixing procedure

Load compoundDump

05

Step 2:

Filling of the chamber of the Brabender with gum rubber, lowering of the Plunger.Raising of the plunger and adding ZnO, stearic acid, ½ silica and ½ silane (if the masterbatch preparation was with silane), lowering of the plunger.Raising of the plunger and adding ½ silica and ½silane (if the masterbatch preparation was with silane), lowering of the plunger.SweepDump of the masterbatch

0

1

2

46

ActionTime (mins.)

Step 1:

Curatives: added on a two roll mill

Curing: Wickert laboratory press WLP 1600/5*4/3 at

160°C, 100 bar

Mixing: Brabender 350S

12

ð Payne effect (RPA 2000, Alpha Technologies)

ð Bound rubber content

ð Cure characteristics (RPA 2000, Alpha Technologies)

ð Reinforcement parameter (αF)

ð Tensile properties (Zwick Z020)

ð Relative ranking of cross-link density (1/Q)

ExperimentalCompounds testing

13

Plasma polymerization of acetylene and

thiophene onto silica fillers

14Results & discussion

0 2 4 6 8 10 12 14 160,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0

0 2 4 6 8 10 12 14 160,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0W

eigh

t of w

ater

pen

etra

tion

(g)

Time (mins.)

Untreated silica PA-silica PTh-silica

Hydrophobicity: penetration

15Results & discussion

100 200 300 400 500 60088

90

92

94

96

98

100

100 200 300 400 500 60088

90

92

94

96

98

100

100 200 300 400 500 60088

90

92

94

96

98

100W

eigh

t (%

)

Temperature oC

Untreated silica

PTh-silica PA-silica

Weight loss (TGA)

16

Untreated

Results & discussionChemical composition of the surface: ToF-SIMS

PA-treatedC2H3

PA-clusters

C10H10

17

Untreated

Results & discussionChemical composition of surface: ToF-SIMS

C10H10

C2H3NaH

PTh-treated

PTh-clusters

18

Plasma-acetylene and -thiophene silica

reinforced S-SBR and EPDM

19Results & discussionPayne effect (Filler-filler interactions)

SU SPA SPTh ST EU EPA EPTh ET0.0

0.4

0.8

1.2

1.6G

'(0.5

6%) -

G'(1

00.0

4%) [

MP

a]

Sample code

20Results & discussionBound rubber content

SU SPA SPTh ST EU EPA EPTh ET0

10

20

30

40

50

60

70

Bou

nd ru

bber

con

tent

(%)

Sample code

21Results & discussionReinforcement parameter

SU SPA SPTh ST EU EPA EPTh ET0

2

4

6

8

10R

einf

orce

men

t par

amet

er (α

F)

Sample

22Results & discussionStress-strain behavior: S-SBR

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

Strain (%)

Stre

ss (M

Pa)

SU

ST

SPA SPTh

SU

SPAST

SPTh

23Results & discussionStress-strain behavior: EPDM

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

Strain (%)

Stre

ss (M

Pa)

EU

ET

EPA EPTH

EU

EPAET

EPTh

24Results & discussionRelative ranking of cross-link density

SU SPA SPTh ST EU EPA EPTh ET0.0

0.1

0.2

0.3

0.4

0.5

0.6R

elat

ive

rank

ing

of c

ross

link

dens

ity (1

/Q)

Sample code

25

Summary

Acetylene and thiophene plasma coating:_ Silica is coated successfully by plasma acetylene- and thiophene-treatment

_ Reduced polarity of the silica due to plasma coating

Comparison of acetylene and thiophene plasma treatment in S-SBR:

_ Higher reduction in filler-filler interaction (Payne effect) due to PA-silica

_ PTh-silica shows highest bound rubber content

_ Dispersion is improved in the case of PA-silica

_ Compared to PA-silica, PTh-silica shows the best tensile properties whichcorrelates with the relative ranking of cross-link density

26

Summary

Comparison of acetylene and thiophene plasma treatment in EPDM:

_ PTh-silica shows higher reduction in filler-filler interaction (Payne effect)

_ Bound rubber content is highest in PA-silica

_ PTh-silica shows the best dispersion

_ PA- and PTh-silica shows improved tensile properties but PA-silica shows

higher moduli at 100% and 300%

_ Tensile properties are in correlation with the relative ranking of cross-link

density

_ PA-silica shows improved compatibility and interaction of fillers with

EPDM

27

Acknowledgements