Wet grip

Natural mbber was also used extensively in its oil-extended form in winter tires in the 1970s (57). Use of oil-extended natural mbber treads, found to have excellent traction on ice and snow, superseded studded synthetic mbber treads when studs were banned in certain countries and states owing to the damage they cause to partially cleared roads. This concept has been extended into aH-season tires, which account for over 75% of original equipment and replacement tires in the United States. It has been shown (58) that part replacement of styrene—butadiene mbber (SBR) in the formulation of aH-season tire tread compounds with oil-extended natural mbber increases ice and snow traction, reduces rolling resistance, and has no effect on normal wet grip. Also, there is only a minor trade-off in wear performance, because below a tire surface temperature of approximately 32°C, the wear of natural mbber is superior to SBR, whereas above this temperature the reverse is tme (59). Thus, wear of an aH-season tire ultimately depends on the surface temperature of the tread over its annual cycle of temperatures. 

Polybutadiene is produced by solution polymerisation, and one important feature governing the performance of the resultant polymer is the cis 1,4, and 1, 2 vinyl contents. High cis 1,4 polymers (>90%) have a Tg around -90 °C, and hence exhibit excellent low temperature flexibility only exceeded by the phenyl silicones. They also exhibit excellent resilience and abrasion resistance unfortunately the high resilience gives poor wet grip in tyre treads, and hence this rubber finds limited use as the sole base for such compounds. 

Selecting the appropriate glove materials with epoxy resins systems involves matching the characteristics of the glove with the requirements of the production task. Glove resistance characteristics can be classified as either physical or chemical. Physical characteristics of production tasks are dexterity wet grip and cut, tear, puncture, and abrasion resistance. Chemical characteristics are dependent on the aggressiveness of the resins, solvents, and other materials. 

Hi. Applications in tyre manufacturing. Two important properties of tyres are the so-called rolling resistance and the wet grip, which both depend on the physical characteristics... 

For the loss tangent properties, the magnitudes of tan 5 for both CB and SSF composites are similar. The magnitude of tan 5 has practical importance in rubber applications such as tires. A rubber composite that has a smaller tan 5 value tends to have a reduced rolling resistance and save energy, while a larger tan 6 tends to have an improved skid resistance and wet grip. The ability of SSF to absorb some moisture in a wet state tends to reduce G , increase tan 5, and lead to better wet traction. 

Wet grip or traction improves nearly linearly with the increase in compound Fg. 

Figure 9.2 shows the effect of Fg on wet skid. If an increase in wet grip is required with minimum impact on rolling resistance, then a change in Tg is best accomplished via an increase in the vinyl-butadiene level rather than in the bound styrene content. Alternatively, if wear is of higher importance, Fg should be adjusted by a change in the bound styrene level. The optimum... 

Tg could therefore be obtained by adjustment of either the vinyl-butadiene or styrene contents to obtain the required wet grip, rolling resistance, and wear performances. It has been demonstrated (Mezynski and Rodgers, 1989 Saito, 1999 Oberster et al., 1973) that an increase in wear performance would lead to a trade-off in traction performance (Figure 9.3). 

Uses TPE alloy for wet grip overmolding applies, such as grips for hand tools, kitchen utensils, and houseware items Properties BIk. color sp.gr. 0.80 tens. str. 465 psi elong. 552% hardness (Shore A) 55 Versaflow Base [Shamrock Tech.]... 

Foamed coating provides open surface texture to clear liquids from surfaces for firm wet-grip... 

The softening point is the temperature at which a material softens or becomes less viscous beyond some arbitrary softness or viscous. A softening point of the al-kyd resin is preferably at least -40°C or at most 30°C in order to obtain sufficient tackiness and to avoid excessive increase in hardness and rolling resistance which then will further lower its wet grip performance. 

From a viscoelastic point of view, a high-performance tire should have a low tan 8 value at 50 to 80°C to reduce rolling resistance and save energy. The ideal material should also possess high hysteresis from -20 to 0°C, for high skid resistance and wet grip. 

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