It is known that the hysteresis component of friction greatly contributes to the wet traction of tires, because the lubricant film prevents the tires from contacting the road. There are a lot of studies that have compared the wet skid resistance and the hysteresis loss of rubber. However the adhesion component of friction should also be evaluated.
In this paper, the friction forces are measured when rubbers are rubbed against the lubricated metal gauze. The variations of the friction force with the sliding speed are different from the hysteresis loss of the rubbers. At the low sliding speed region, the rubber specimens partially contact with the metal gauze and the contact area decreases with increasing sliding speed. At that time, the friction forces also include the adhesion component together with the hysteresis component.
The adhesion component of friction for rubbers rubbed against the wet metal gauze depends on the directly contacted area on to the metal gauze and shear strengths of the rubbers. Especially silica-filled SBRs have an effect to raise the adhesion component of friction at low sliding speed.

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Methacrylic acid(MA) was used to modify the surface of polyurethane elastomer(PUE)by an electrophoresis method. Thermal properties, morphology, and abrasion resistance of the modified PUE were studied by means of DSC, polarizing microscope, swelling test, dynamic mechanical test, and abrasion test. The glass transition temperature of the modified PUE shifted towards the higher temperature range. Results of the microphotographs showed that aggregation structure of the hard segments(spherulite) of the PUE was destroyed by the PMA. The surface of the modified PUE containing high PMA content had a broader main transition peak with a small shoulder in temperature dependence of tanδ and the main peak shifted towards higher temperature, indicating the phase separation to some extent. The modified PUE exhibited higher abrasion resistance compared with the unmodified PUE.

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Temperature dependence of storage modulus was studied as a function of structural changes of black filled rubber systems. Above 10°C, the storage modulus (E') of black filled rubber systems decreased with increasing a temperature. The change was dependent on the content and grade of carbon black in the filled rubber systems. NMR results revealed that black filled rubber system had a multi-component system depending on the mobility of rubber molecules, which was a function of temperature. The amount of less mobile rubber component decreased with increasing the temperature without noticeable changes in the mobility. The temperature dependence of the E' was affected by the amount of less mobile rubber molecules which was primarily determined by the specific surface area of carbon black. The relation between occluded rubber structure and less mobile rubber component was also discussed. Based on the results, the structural changes of occluded rubber with temperature were proposed.

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