Rubber Contact Phenomena

Research on rubber wiper blades led to the establishment of the now widely used JKR equilibrium equation that determines the strength of adhesion between surfaces. The equation was adapted to allow for the viscoelasticity of rubber, leading to explanations of how adhesion can impact on tack, rebound resilience, and rolling, static and sliding friction. The adhesion of rubber to ice was found to depend on salt concentration in the ice thus providing insight into winter tire performance. The development of optical techniques has greatly aided studies, particularly for measuring the thickness of thin liquid films sandwiched between contact surfaces. Measurements on water films squeezed between rubber and glass revealed the action of repulsive forces that can reduce adhesion and hence friction. The efficacy of water lubrication depends upon whether surfactants are present, and upon the acidity or alkalinity of the water. Improved understanding of adhesion and friction mechanisms offers design guidance for a range of rubber articles.