Friction Properties and Mechanism of TPU/HVSSBR Composites under Different Interface Conditions

Thermoplastic polyurethane (TPU) has been widely used due to its wear resistance, hydrolysis resistance, tear resistance, bending resistance and other characteristics. As a sole material, the most prominent problem is the lack of skid resistance. In this study, high vinyl solution polymerized styrene butadiene rubber (HVSSBR) was blended with TPU to improve the skid resistance of TPU materials. The LAT-100 machine was used to test the changes of friction coefficients of TPU/HVSSBR composites with different blending ratios on dry or wet surfaces and at different ice surface temperatures (−20, −10 and −5 ℃) under constant surface pressure. The results showed that the incorporation of HVSSBR phases can improve the dry friction coefficients f_D, wet friction coefficients f_W and ice friction coefficients f_I of TPU. In which the f_D, f_W of TPU/HVSSBR=60/40 increased respectively by 35% and 13%, and the f_I at different ice surface temperatures (−20, −10 and −5 ℃) increased respectively by 59%, 89% and 116%. Also, combined with the tribological theory, the skid-resistant mechanism under different interface conditions of the composites was analyzed by fitting the f_D, f_W, f_I with the influence parameters of loss factor tan δ and hardness H. It was found that f_D, f_W, f_I had a linear positive correlation with tanδ/H, the correlation was: wet friction > ice friction > dry friction. It indicated that the mechanism of wet friction and ice friction conformed to the adhesion friction model, and the dry friction was the result of the joint action of adhesion friction and hysteresis friction.