Tire Treadwear—The Joint Influence of Compound Properties and Environmental Factors

Abstract

Abstract The wear rate of tire tread compounds depends jointly on the properties of the compound and on certain tire use or environmental factors. A previous publication clearly demonstrated the influence of rubber glass transition temperature (Tg) and carbon black (reinforcement) level under varying seasonal conditions (summer vs. winter testing) for several test courses with varying levels of pavement microtexture or abrasiveness. The variations in treadwear performance were interpreted in terms of two mechanisms of wear: (1) a highly elastic rupture deformation mechanism, rubber element vs. pavement asperity, called E-wear and (2) a highly viscous or plastic deformation mechanism (abrasive wear), called P-wear. The work of the previous publication has been extended by the use of the compound loss modulus (at 0 °C) as a single property to characterize tread compounds, that is superior to other typical properties (hardness, fatigue flex life, rupture energy). The varied dependence of wear on loss modulus (negative, zero, positive dependence) is explained on the basis of the two mechanisms. Thus an increase in loss modulus may have beneficial or detrimental effects on wear rate depending on the loss modulus level and certain environmental factors. The loss modulus is dependent on Tg, the carbon black level and morphology, the process oil content, as well as certain polymer microstructure properties such as cis/trans ratio and block (polymer) characteristics. The measured loss modulus is capable of being expressed in terms of components attributable to the above properties. The use of these components opens up the possibility of accurately characterizing tread compounds for their treadwear performance under selected environmental conditions and thus improve on the largely trial and error process of tread compound development.