Wet Friction: - Rubber News

Paper No. XXX

Effects of SBR Polymer Microstructure on Key Properties in Carbon Black and

Silica Filled Tread Compounds

Glenn Denstaedt*, Bin Chung, Gwen Mouzon, James Holt, Bryan Howell

Maxxis Technology Center

Maxxis/Cheng Shin Tire USA

480 Old Peachtree Road

Suwanee, GA 30024

Presented at the ITEC 2010 International Tire Exposition and Conference

Cleveland, Ohio USA

September 21-23, 2010

*Speaker

Abstract

Effects of polymer microstructure on key tread properties are well known in a given filler

system. This study is designed to compare and contrast effects of carbon black and silica

across a broad range of SBR polymer microstructures. Statistical models will be

discussed which develop insight into performance characteristics relevant to the tread

compound "Magic Triangle" of wear resistance, traction and rolling resistance.

I. Introduction

Polymer and filler selection are key in obtaining desired tread compound performance.

Significant discussion around the effects of this selection centers on optimization

treadwear, traction and rolling resistance of the tread compound. This is also known as

the “Magic Triangle” of tread compound performance (Figure 1). The compounder’s

paradigm is that in a typical system, when performance is optimized for one factor there

is a corresponding negative impact on one or both of the other properties. In essence you

can change the shape of the triangle but not the total area. “Breaking out of the Triangle”

requires techniques that will change the area of the triangle by improving one or more

properties without a loss in the others.

1. Polymer Structure

The largest body of knowledge compares polymer microstructure, macrostructure and

chain end functional groups in carbon black filled systems. Changes in polymer

macrostructure and functional groups are know to have specific effects on compound

hysteresis by either reducing the number of chain ends or modifying the mobility of the

polymer chain ends which contribute to compound hysteresis. Typically changes in

polymer functional groups are targeted specifically to the filler system in the compound.

Changes in chain end functional groups (i.e. Tin coupling) are targeted toward hysteresis

reduction in carbon black filled compounds.1 Polymer backbone functional groups are

targeted toward improving interaction between silica and the polymer through chemical

attachment.2 Polymers with these types of modifications are not studied in this work.

Changes in polymer macrostructure, including average molecular weight and molecular

weight distribution, are also know to effect hysteresis of compounds through changes in

the number of mobile chain ends.3 In this study, polymers were selected to have minimal

variation in macrostructure to eliminate this effect on overall compound performance

compared to the changes in basic microstructure of the polymer.

Modification of styrene butadiene polymer microstructure is well known to have

significant impact on major tread performance properties. Specifically, changes in

styrene content and the amount of vinyl groups (Figure 2) in the butadiene polymer chain

impact the glass transition temperature, Tg, which has a major impact in wet traction

performance. The regression equation of styrene and vinyl content terms to Tg as a

response, based on the polymers selected in this study, is also shown in Figure 2. In

carbon black filled compounds, it is well documented that the optimization of traction

properties comes with the, less optimum, trade offs of increased hysteresis and reduced

abrasion resistance.4,5,6

Effects of SBR polymer microstructure in silica filled systems with coupling agent are

less defined. This study is designed to compare and contrast effects of carbon black and

silica across a broad range of SBR polymer microstructure.

2. Reinforcing Fillers: Carbon Black and Silica

In the absence of coupling agent, carbon black and silica have similar hydrodynamic

reinforcement of polymer through polymer and filler interaction leading to improvements

in tensile and tear properties. The key difference between the fillers is that carbon black

is hydrophobic and more compatible with the non-polar polymers leading to improved

dispersion and increased interaction between the polymer and filler. Silica is hydrophilic

and incompatible with the non polar polymers leading to decreased polymer filler

interaction and the typical poor modulus development in uncoupled silica compounds.

Strong aggregate structures are also evident due to hydrogen bonding between silanol

groups on the silica filler surface leading to significant difficulty in maintaining good

dispersion. In common silica containing passenger and light truck treads, organosilane

coupling agents improve polymer filler interaction through bonding of the silane to the

silica filler during reactive mixing and direct covalent bonding of the mercaptosilane to

the polymer chain during vulcanization. This leads to improved modulus development

and abrasion resistance. Decreased mobility across the polymer chain would be expected

due the strong chemical bonding with the organosilane modified silica leading to reduced

hysteresis.7,8

II. Experimental

1. Polymers and Formulas

Compound formulas consisted of 100 phr polymer, either 72 phr N234 carbon black or

85 phr of Ultrasil 7000GR silica with 9 phr NEX coupling agent and 37.5 phr oil. Filler

quantities were determined based on an equal volume basis with adjustments made to

compensate for moisture pick up and subsequent loss during mixing for the silica

containing compounds. Additive and curative levels were adjusted based on the filler

system used and industry recommendations (Table 1). Commercially available styrene

butadiene polymers were selected with varied styrene and vinyl content representing Tg’s

ranging from -70 to -20 degrees C (Table 2).

2. Mixing Procedures

Compounds were mixed in a Farrel BR1600 laboratory banbury using the 3 stage mix

procedures shown in Table 3. Differences in mix procedures between carbon black and

silica containing formulas pertain to the added temperature equilibration and 5 minute

hold at 160 degrees C steps to allow for the reaction between the silica filler and silane

coupling agent (silanation) required to achieve optimum properties in silica compounds.

Compound test samples were cured to an approximate 100% state at 160 deg C as

determined by moving die rheometry at the same temperature and sample geometry.

3. Compound Testing

a. Physical Properties

Basic compound testing including Stress-Strain, Hardness and Rebound were conducted

using accepted ASTM methods in triplicate with median values reported. Stress-Strain

properties were measured at room temperature on a United six station tensile tester in

accordance with ASTM D412. The Zwick automated rebound tester was used to

measure resilience at room temperature (DIN 53512/ISO 4662). Hardness was measured

using an automated Shore A2 durometer (ASTM D 2240).

b. Abrasion

The FPS (Field Performance Simulation) Wear Testing System, a modified Lambourn

style abrasion tester manufactured by Ueshima Seisakusho Co, Ltd., was used to generate

wear rate data in millimeters wear per 1000 kilometers of travel. The equipment is

designed to provide variable load (0 – 50N) capability at variable slip ratio (0 – 20%) in

either driving or breaking modes. Talc is applied to the 120M safety walk surface at a

variable rate to prevent material build up and simulate road conditions. Test conditions

were determined based on parametric studies of the equipment.9 Slip ratios were set at 7,

9, 11, 13, and 15% at constant sample wheel speed (driving mode) and 35N load. Models

were developed at 15% slip due to higher discrimination and higher model significance.

c. Wet Friction

A Ueshima Model FR-6050 Outside Drum Friction Tester was used to evaluate the

friction characteristics of the design compounds. The test sample is applied at variable

load (0-300N) to a 1 meter diameter test drum covered with 240 Mesh safety walk

generating a sample speed of between 0 and 50kmph. The test machine can operate

between 10 and 60 degrees C with water flow rates between 0 and 3000 cm3/min

allowing for either wet or dry friction testing. Torque is applied at a breaking rate of 16.7

kmph per second applied to the sample and a resultant friction force curve is generated

from 0 to 90% slip ratio. The maximum coefficient of friction, Mu_P(eak) is determined

and used for analysis of compound performance. Specific conditions for this study

(Load=75N, Speed=30,40,50kmph and water flow rate of 1500cm3/min) were determined

by parametric study to represent typical conditions relevant to tire traction testing.10

d. Dynamic Testing

Dynamic testing was conducted at -10 and 60 degrees C to characterize wet friction and

rolling loss parameters respectively using a Metrovib Model VA3000 viscoanalyzer.

Testing was conducted in shear at both temperatures. At -10 deg. C, strain was set a 1%

with a frequency of 5Hz. Tangent delta and Complex modulus, G*, were included in

comparisons to wet friction results. At 60 deg. C, testing was conducted using a strain

sweep from 0.1 to 12% strain and 10Hz. Maximum tangent delta is used to correlate to

hysteresis related to rolling loss. Delta G’ characterizes the Payne effect (filler-filler

interaction) and is used to assess the effectiveness of the organosilane – silica coupling

reaction.

4. Statistical Modeling

Modeling was conducted for the key applications properties using Stat-Eaze® Design

Expert® 7 statistical design software. Responses were modeled against polymer Tg as

well as polymer microstructure (% styrene and % vinyl content). Additionally, low

temperature dynamic properties were modeled against Wet Friction responses.

III. Results and Discussion

1. Compound Physical Properties

a. Hardness

In both carbon black and silica containing compounds hardness increased with increasing

polymer Tg (Figure 3). Silica compounds exhibited lower overall hardness levels in all

polymers studied than the corresponding carbon black containing compounds.

b. Stress Strain

The modulus of the compounds increases with increasing polymer Tg. Modulus values

at 300% are shown in Figure 4. At lower polymer Tg levels, the silica containing

compounds exhibited lower modulus levels than corresponding carbon black containing

compounds. Modulus values of the silica compounds were equivalent to the carbon black

compounds at the high polymer Tg levels.

No specific correlation is evident between polymer Tg and tensile values (Figure 5).

Carbon black containing compounds trend to lower tensile with increases in polymer Tg.

Tensile values of the silica compounds were typically lower that the carbon black

compounds at the low to medium polymer Tg levels which is expected in compounds that

use coupling agents with silica. At high polymer Tg, tensile levels of the silica

containing compounds approached those of the carbon black compounds.

c. Rebound

Rebound results are shown in Figure 6. Significant reductions in resilience were

observed as polymer Tg increased in both silica and carbon black containing compounds.

At all polymer Tg levels, the silica containing compounds exhibited higher resilience

than the corresponding carbon black compounds.

2. Abrasion

A head to head comparison of carbon black and silica filled compound abrasion at 15%

slip, across the polymer range, is shown in figure 7. Linear wear rate in mm/1000km

increases with both reinforcing fillers as polymer Tg increases. While overall trends

were similar, the silica compounds demonstrated slightly improved performance, lower

linear wear rate, than the carbon black compounds. This is also indicative of effective

coupling of the silica compounds. The lack of chemical interaction between the filler and

polymer in uncoupled silica compounds would lead to high linear wear rates. Figure 8

illustrates abrasion performance across the range of slip ratios, from 7% to 15%.

For both carbon black and silica compounds, common trends of increasing wear rate with

increasing polymer Tg are exhibited at all but the lowest, least sensitive, slip ratios.

Comparisons of linear wear rate at each slip ratio indicated strong correlation to polymer

Tg across the entire range of polymers used with no cross over between slip ratios.

Polymer microstructure (Styrene and Vinyl content of the polymers) was modeled against

linear wear rate at 15% slip ratio using stepwise linear regression of linear, interaction

and quadratic terms (Figure 9). Models of polymer microstructure were highly

significant in both Carbon Black and Silica containing compounds.

Carbon Black Compounds: Linear Wear Rate (mm/1000km) = 4.7 (%vinyl) + 300

R2 = 0.94

Silica Compounds: Linear Wear Rate (mm/1000km) = 3.5 (%vinyl) + 265

R2 = 0.96

Models indicate increased linear wear rate (poorer abrasion resistance) with increasing

vinyl content in both carbon black and silica containing compounds. Styrene content was

an insignificant term in both filler systems.

3. Wet Friction

Wet friction results at 50kmph are shown in Figure 10 for carbon black and silica

containing compounds. Expected increases in wet friction with increased polymer Tg are

evident. The carbon black and silica compounds were equivalent through the mid range

in polymer Tg with carbon black exhibiting higher levels in the high Tg polymers.

Friction results with varied speed (Figure 11) illustrate the typical response of increased

wet friction with reduced speed. In the carbon black containing compounds, results show

consistent increases in wet friction, and strong correlation, with increased polymer Tg at

all speeds. The silica containing compound response is similar to carbon black at

50kmph, but flattens out at lower speeds. At 30kmph, there is little change with

increasing polymer Tg and wet friction of the silica filled compounds is higher than

carbon black in the lower Tg polymers. Comparative modeling of polymer

microstructure (vinyl and styrene content) between carbon black and silica

filled compounds was conducted at the higher 50kmph speed.

Carbon Black Compounds: Mu_P (50kmph) = 0.014 (%vinyl) + 0.67 R2 = 0.99

Silica Compounds: Mu_P (50kmph) = 0.011 (%vinyl) + 0.75 R2 = 0.99

As with abrasion, friction effects were solely related to the vinyl content in the polymers

(Figure 12). Increased vinyl content in the polymer lead to increased wet friction in both

filler systems.

It is generally accepted that both low temperature hysteresis (tangent delta) and

compound stiffness can be predictors of wet friction performance.

Models were developed for wet friction evaluating all relevant low temperature (-10

degrees Celsius) dynamic properties. Consistent with general knowledge, tangent delta

and dynamic modulus were the most significant terms in models generated. Carbon

black and silica containing compound models of low temperature properties as predictors

of wet friction performance are shown in Figure 13. In the carbon black system, strong

correlation between the combination of low temperature tangent delta and dynamic

modulus, G*, are exhibited.

Carbon Black: Mu_P (50kmph) = 0.606 (tangent delta) + 0.0021 (G*) + 0.925

R2 = 0.98

Wet friction increases with increasing tangent delta and increasing dynamic modulus. In

the silica system, dynamic modulus was the only significant factor in predicting wet

friction.

Silica Compounds: Mu_P (50kmph) = 0.021 (G*) + 0.81 R2 = 0.95

As with carbon black, increased wet friction results were evident with increasing

dynamic modulus.

4. Hysteresis

Compound hysteresis related to tire rolling resistance was evaluated using previously

discussed dynamic properties at 60 degrees Celsius. Tangent delta values comparing the

carbon black and silica filled compounds are shown in Figures 15 and 16. The expected

increase of tangent delta with increasing polymer Tg is evident in the carbon black

containing compounds. The silica compounds did not exhibit a significant hysteresis

trend with increasing polymer Tg, however; hysteresis was lower in the high Tg polymers

than in polymers at lower Tg levels. All silica compounds are at significantly lower

hysteresis levels than the carbon black containing compounds. The change in storage

modulus from low to high strain (Delta G’) is illustrated in Figure 14. The carbon black

compounds show typically high Delta G’ values due to high levels of filler-filler

interaction at low strain (Payne effect). The silica compounds have very low delta G’

indicating effective coupling with the polymer and increased dispersion throughout the

polymer matrix leading to low filler-filler interaction. It is likely that the good dispersion

and covalent bonding of the filler to the polymer chain are limiting the mobility of

polymer consistently across the entire chain leading to the reduced hysteresis levels.

Models of dynamic properties vs styrene and vinyl content are shown in Figure 16. At

60 deg C, both vinyl and styrene content increases increased hysteresis in the carbon

black filled compounds.

Carbon Black: Tangent Delta = 0.0069 (%styrene) – 0.0011 (%vinyl) + 0.134

R2 = 0.99

While correlation of hysteresis to Tg shows little sensitivity in the silica filled system, a

reasonable model was generated with the separate components of vinyl and styrene

content.

Silica Compounds: Tangent Delta = 0.011 (%styrene) – 0.0033 (%vinyl) + 0.032

R2 = 0.86

As with carbon black, hysteresis increased with increasing styrene content. Neither filler

would have strong interaction with the chemically stable styrene units. The opposite

effect was shown with reduced hysteresis of silica compounds at higher vinyl content.

While reaction rates and chemical bonding were not studied, it can be inferred that

carbon black would have relatively low interaction with the polymer vinyl groups and the

silica-organosilane complex would readily react with the accessible vinyl group through

covalent bonding.

IV. Summary

In carbon black filled compounds, published trends are confirmed. Polymer Tg and

measured properties were well correlated. As polymer Tg in the compound increased so

did hardness, modulus, hysteresis (at all temperatures) and wet friction results. Abrasion

resistance decreased (linear wear rate increased) with increasing polymer Tg. Similar

trends for physical properties, wet friction and abrasion were also noted for the silica

containing compounds. Statistical modeling of polymer microstructure (styrene and

vinyl content) indicated that the key factor in both wet friction and abrasion was the vinyl

content. Increases in vinyl content increased wet friction and reduced abrasion

resistance. This was consistent in both carbon black and silica containing compounds.

Key differences were noted between the reinforcing fillers for high temperature

hysteresis properties. Carbon black containing compounds exhibited the typical effect of

increasing hysteresis with increasing polymer microstructure. As both styrene and vinyl

groups in the polymer increased so did hysteresis indicative of lower interaction between

the polymer and carbon black in regions containing these groups. The silica compounds

exhibited lower hysteresis across the polymer Tg range than carbon black. The hysteresis

of the silica containing compounds increased with increases in the chemically stable

styrene unit. As the vinyl content of the polymer increased, hysteresis decreased.

Increased efficiency of covalent bonding with increased vinyl content is attributed to

reductions in polymer mobility and reduced hysteresis.

The “Magic Triangle” of the key performance properties of abrasion (treadwear), Friction

(Traction) and hysteresis (Rolling Resistance), is shown in Figure 17. The carbon black

triangle illustrates the typical level of expected properties. Any movement in one

parameter will be to the detriment of one or both of the other properties. Breaking out of

the triangle is illustrated in the silica containing compounds where Abrasion and Wet

Friction levels can be maintained equivalent to the carbon black compounds but

significant hysteresis advantages can be gained.

V. Future Work

Instead of pure polymer compounds, future work will evaluate the more practical

compound approach of using 2 and 3 polymer blends to modify performance of key tread

properties. Evaluations will include blends of high Tg SSBR, low Tg SSBR and BR

polymers as well as extend studies to Natural Rubber containing compounds.

Performance changes will be compared to changes in the blend Tg to determine if the

relationships of Tg to performance hold with blends of polymers as opposed to single

polymer compounds.

Acknowledgements

The authors wish to acknowledge and thank their colleagues at the Maxxis Technology

Center for their effort and assistance in conducting this study. Special thanks are

extended to Maxxis/Cheng Shin Rubber for permission to publish this paper.

References

1. F. Tsutsumi, M. Sakakibara, and N. Oshima, “Structure and Dynamic Properties of Solution SBR Coupled with Tin Compounds”, Rubber Chem.Technol., 63, 8, (1990).

2. J. Hannay, “New Solution SBRs to Meet Future Performance Demands”,

International Tire Expo and Conference, September 2008, Paper 11A

3. D. Moore, G. Day, “Comparison of Emulsion vs Solution SBR on Tire

Performance, ACS Rubber Division meeting, Washington DC, 1985, Paper 49

4. Science and Technology of Rubber, Second Edition, edited by J. Mark, B. Erman, and F. Eirich, W. Barbin and M. Rodgers, 1994

5. W. Kern, S. Futamura, “Effect of Tread Polymer Structure on Tire Performance”,

Polymer, Vol. 29 n. 10, 1801, (1988)

6. G. Day, S. Futamura, “A Comparison of Styrene and Vinyl Butadiene in Tire Tread Performance, Kauch Gummi Kunstat, Vol 40, 39, (1987)

7. Rubber Technology, edited by John S. Dick, W. Waddell and L. Evans, 2001

8. M.-J. Wang, Y. Kutsovsky, “Effect of Fillers on Wet Skid Resistance of Tires,

ACS Rubber Division meeting, Cleveland, OH, 2007, Paper 27.

9. B. Holwell, B. Chung, G. Denstaedt, R. Lou, “A Parametric Study on Abrasion Wear of Rubber Compounds using Ueshima’s FPS Abrasion Tester”, International Tire Expo and Conference, September 2010

10. J. Holt, B. Chung, G. Denstaedt, ”A Parametric Study on Rubber Friction”,

International Tire Expo and Conference, September 2010

Figures and Tables

Figure 1: “Magic Triangle of Tread Compound Performance.

Figure 2: SBR Polymer Microstructure: Tg vs Styrene and Vinyl content.

Tg = 1.11(%Styrene) + 0.97(%Vinyl) – 101 R2 = 0.99

% Styrene % Vinyl

Carbon Hydrogen

Treadwear(Abrasion)

Wet Traction(Wet Friction)

Rolling Resistance(Hysteresis)

Magic Triangle

Treadwear(Abrasion)

Wet Traction(Wet Friction)


Magic Triangle

Table 1: Compound Formulas

Table 2: Polymers used in study.

Duradene®: Firestone Polymers Buna VSL®: Lanxess

% Styrene % Vinyl Tg (Deg C)Duradene® 711 18 11 -70Duradene® 750 18 14 -70SBR1712 23.5 20 -55Buna VSL® 2525-0 25 25 -49Buna VSL® 5025-1 25 50 -24Buna VSL® 5228-2 28 52 -20

Materials 1 2Polymer 100 100

Carbon Black N234 72Silica Ultrasil 7000GR 85

Coupling Agent 9Oil 37.5 37.5

Processing Aid 2 3Zinc Oxide 4 3

Stearic Acid 2 1.56PPD 2 2WAX 1.5 1.5CBS 1.5 1.7DPG 0.3 2

Sulfur 2 1.5

Formula PHR

Table 3: Mixing Procedure

Carbon Black Mix Procedure Silica Mix Procedure

StageTime (min)

Temp (Deg C) Action Stage

Time (min)

Temp (Deg C) Action

1-MB 0 60 Add Polymer 1-MB 0 60 Add Polymer(77 rpm) 0.5 80 Add Carbon Black (115 rpm) 0.5 80 Add ½ Silica, Coupling Agent

1.5 90 Add ZnO, SA, AO, Wax, PA 1 90 Add ½ Silica, Oil2 110 Sweep 1.5 110 Sweep3 120 Add Oil 2 120 Add ZnO, SA, AO, Wax, PA

4.5 160 Dump 2.5 130 Sweep, increase RPM50 mill, sheet off 3 160 Hold at temp 5min

8 160 Dump50 mill, sheet off

2-Remill 0 60 Add Stage 1 MB 2-Remill 0 60 Add Stage 1 MB(115 rpm) 1 120 Sweep (115 rpm) 1 120 Sweep

3 150 Dump 3 150 Dump50 mill, sheet off 50 mill, sheet off

3-Final 0 50 Add polymer and curative 3-Final 0 50 Add polymer and curative(77 rpm) 1.5 90 Sweep, RPM to 50 (77 rpm) 1.5 90 Sweep, RPM to 50

3.5 110 Dump 3.5 110 Dump50 mill, sheet off 50 mill, sheet off

Figure 3: Physical property results: Hardness. SBR Polymer Microstructure: CB vs Silica

Hardness

40.00

45.00

50.00

55.00

60.00

65.00

70.00

75.00

SSBR(18/11)-70C SSBR(18/14)-70C ESBR(23/20)-55C SSBR(25/25)-49C SSBR(25/50)-24C SSBR(28/52)-20C

Polymer (Styrene/Vinyl%) Tg

Shor

e A

Carbon Black Silica

Figure 4: 300% Modulus results.

SBR Polymer Microstructure: CB vs SilicaPhysical Properties: Modulus

0.00

2.00

4.00

6.00

8.00

10.00

12.00



M30

0 (M

Pa)

Carbon Black Silica

Figure 5: Physical Property results: Tensile SBR Polymer Microstructure: CB vs Silica

Physical Properties: Tensile

5.00

7.00

9.00

11.00

13.00

15.00

17.00

19.00

21.00

23.00

25.00



Tens

ile (M

Pa)

Carbon Black Silica

Figure 6: Physical property results: Zwick Rebound

SBR Polymer Microstructure: CB vs SilicaZwick Rebound

0.0

10.0

20.0

30.0

40.0

50.0

60.0



Reb

ound

%

Carbon Black Silica

Figure 7: FPS Abrasion comparison. SBR Microstructure: CB vs Silica

FPS Abrasion: 15% Slip Ratio

100

150

200

250

300

350

400

450

500

550

600

SSBR(18/11)-70C SSBR(18/14)-70C SBR(23/20)-55C SSBR(25/25)-49C SSBR(25/50)-24C SSBR(28/52)-20C


Line

ar W

ear R

ate

(mm

/100

0km

)

Carbon Black Silica

Figure 8: FPS Abrasion at various slip ratios vs Polymer Tg. SBR Polymer Microstructure: Carbon Black

FPS Abrasion

y = 3.8166x + 617.66R2 = 0.9289

y = 2.2668x + 390.41R2 = 0.9225

y = 1.3199x + 218.02R2 = 0.9355

y = 0.5561x + 97.34R2 = 0.9242

y = 0.1893x + 34.888R2 = 0.9177

0

100

200

300

400

500

600

-80 -70 -60 -50 -40 -30 -20 -10

Polymer Tg (Deg C)

Line

ar W

ear

Rat

e (m

m/1

000k

m)

7% Slip

9% Slip

11% Slip

13% Slip

15% Slip

Linear (15% Slip)

Linear (13% Slip)

Linear (11% Slip)

Linear (9% Slip)

Linear (7% Slip)

SBR Polymer Microstructure: SilicaFPS Abrasion

y = 2.8885x + 503.13R2 = 0.9803

y = 2.4107x + 376.83R2 = 0.9342

y = 1.1116x + 199.16R2 = 0.962

y = 0.2852x + 92.525R2 = 0.6461

y = -0.0086x + 29.388R2 = 0.0603

0

100

200

300

400

500

600

-80 -70 -60 -50 -40 -30 -20 -10

Polymer Tg (Deg C)

Line

ar W

ear R

ate

(mm

/100

0km

)

7% Slip

9% Slip

11% Slip

13% Slip

15% Slip

Linear (15% Slip)

Linear (13% Slip)

Linear (11% Slip)

Linear (9% Slip)

Linear (7% Slip)

Figure 9: Models of FPS Abrasion (linear wear rate) as a function of polymer microstructure.

18.00 20.50 23.00 25.50 28.0011.00

21.25

31.50

41.75

52.00Linear Wear Rate, 15% Slip

A: Stryrene

B: V

inyl

384

416

448

480

512

Carbon Black

LWR 15% (mm/1000km) = 4.7(%vinyl) + 300 R2=0.94

18.00 20.50 23.00 25.50 28.0011.00

21.25

31.50

41.75

52.00Linear Wear Rate, 15% Slip

A: Stryrene

B: V

inyl

327

351

374

398

422

Silica

LWR 15% (mm/1000km) = 3.5(%vinyl) + 265 R2=0.96

Figure 10: Wet Friction comparison at 50kmph.

SBR Polymer Microstructure: CB vs SilicaWet Friction: 50kmph

0.60

0.80

1.00

1.20

1.40

1.60

1.80



Mu_

P

Carbon Black Silica

Figure 11: Wet Friction vs Polymer Tg and various test speeds.

SBR Polymer Microstructure: CB vs SilicaWet Friction: Carbon Black

y = 0.0101x + 1.7614R2 = 0.9711

y = 0.0098x + 1.6325R2 = 0.9909

y = 0.0121x + 1.6718R2 = 0.9858

0.60

0.80

1.00

1.20

1.40

1.60

1.80

-80 -70 -60 -50 -40 -30 -20 -10

Polymer Tg (Deg C)

Mu_

P

CB 30kmph

CB 40kmph

CB 50kmph

Linear (CB 30kmph)

Linear (CB 40kmph)

Linear (CB 50kmph)

SBR Polymer Microstructure: CB vs SilicaWet Friction: Silica

y = 0.0011x + 1.3564R2 = 0.6107

y = 0.0052x + 1.4123R2 = 0.9359

y = 0.0077x + 1.3998R2 = 0.9793

0.60

0.80

1.00

1.20

1.40

1.60

1.80

-80 -70 -60 -50 -40 -30 -20 -10

Polymer Tg (Deg C)

Mu_

P

Silica 30kmph

Silica 40kmph

Silica 50kmph

Linear (Silica 30kmph)



Figure 12: Models of Wet Friction (Mu_P @ 50kmph) as a function of polymer microstructure.

18.00 20.50 23.00 25.50 28.0011.00

21.25

31.50

41.75

52.00Wet Friction, 50kmph

A: Stryrene

B: V

inyl

0.935

1.03

1.13

1.23

1.33

Carbon Black

Mu_P(50kmph) = 0.014(%vinyl) + 0.67 R2=0.99

18.00 20.50 23.00 25.50 28.0011.00

21.25

31.50

41.75

52.00Wet Friction, 50kmph

A: Stryrene

B: V

inyl

0.931

1

1.08

1.15

1.23

Silica

Mu_P(50kmph) = 0.011(%vinyl) + 0.74 R2=0.99

Figure 13: Models of Wet Friction (Mu_P @ 50kmph) as a function of low temperature dynamic properties (G* and Tangent Delta).

0.25 0.36 0.47 0.58 0.6912.06

50.47

88.87

127.28

165.69Mu_P 50kmph

A: TanD -10C

B: G

* -10

C

1.2

1.3

1.4

1.49

1.59

Carbon Black

Mu_P(50kmph) = 0.606(tand) + 0.0021(G*) + 0.925 R2 = 0.98

0.22 0.40 0.58 0.76 0.944.30

9.01

13.73

18.44

23.16Mu_P 50kmph

A: TanD -10C

B: G

* -10

C

0.972

1.04

1.11

1.17

1.24

Silica

Mu_P(50kmph) = 0.021(G*) + 0.81 R2 = 0.95

Figure 14: Comparison of dynamic properties at 60oC, Delta G’.

SBR Polymer Microstructure: CB vs SilicaDynamic Properties: 60C, 0.1 to 12% Strain, 10Hz

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0


Polymer (Styrene/Vinyl) Tg

Del

ta G

' (M

Pa)

Carbon Black Silica Figure 15: Comparison of dynamic properties at 60oC, Tangent Delta.

SBR Polymer Microstructure: CB vs SilicaDynamic Properties: 60C, 0.1-12% Strain, 10Hz

0.10

0.15

0.20

0.25

0.30

0.35

0.40



Max

Tan

gent

Del

ta

Carbon Black Silica

Figure 16: Compound Hysteresis (60oC tangent delta) vs polymer Tg.

SBR Polymer Microstructure: CB vs SilicaTanD vs Tg, 60C

y = 0.0021x + 0.4185R2 = 0.9334

0.10

0.15

0.20

0.25

0.30

0.35

0.40

-80 -70 -60 -50 -40 -30 -20 -10

Polymer Tg (Deg C)

Tang

ent D

elta

Carbon Black

Silica

Linear (Carbon Black)

Figure 17: Models of Hysteresis (tangent delta @ 60oC) as a function of polymer microstructure.

18.00 20.50 23.00 25.50 28.0011.00

21.25

31.50

41.75

52.00TanD 60C Max

A: Stryrene

B: V

inyl

0.289

0.3080.327

0.346

0.365

Carbon Black

Tand max 60C = 0.0069(%styrene) + 0.0011(%vinyl) + 0.134 R2=0.99

18.00 20.50 23.00 25.50 28.0011.00

21.25

31.50

41.75

52.00TanD 60C Max

A: Stryrene

B: V

inyl

0.101

0.141

0.182

0.222

0.263

Silica

Tand max 60C = 0.011(%styrene) – 0.0033(%vinyl) + 0.032 R2=0.86

Figure 18: “Breaking out of the Triangle.”

Magic Triangle

Carbon Black Silica


Traction(Friction)

Treadwear(Abrasion)


Traction(Friction)

Treadwear(Abrasion)

Wet Friction: - Rubber News

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