A New Approach to Rubber Reinforcement

Abstract

Abstract Hysteresis is an important factor in determining the strength of rubber vulcanizates, and the presence of small particle fillers in a rubber increases the hysteresis in at least two ways, (a) hydrodynamically and (b) viscoelastically. The two contributions are additive, the first remaining substantially constant with strain rate and temperature and the second increasing with decreasing temperature. The viscoelastic contribution is attributed to the region of immobile rubber chains close to the surface of the filler particles and has the effect of changing the viscoelastic response of the rubber network. It plausibly accounts for the observation that the strength behavior of a filler-loaded rubber at one temperature is similar to that of a gum rubber at a lower temperature. This change of viscoelastic behavior in the interphase between the polymer and the filler surface leads to a high level of creep even at low strains when filler or other solid particles are present. In the case of a strain-crystallizing rubber such as gum NR, only regions of high strain contain the necessary particulate inclusions. In this circumstance strength is obtained without serious creep in the bulk phase. Thus well-compounded natural rubber gum vulcanizates meet the requirements of a strong rubber with low creep and good resilience to a remarkable degree.