高伸長下における純ゴムの非エントロピー弾性

Abstract

This research investigates the temperature dependence of pure rubber in a stretched state. The motivation for this investigation is a desire to validate the theory on the reinforcement mechanism of rubber by carbon black which we proposed previously in 1982. The structure model of this reinforcement system is a super-network of stretched molecular chains. The reinforcement effect is represented by a separated term, called the γ term, in a strain energy density function (W function) and it has been observed that this γ term has no temperature dependence. The classical rubber elasticity theory, however, predicts that the molecular chains display entropy elasticity even in the nongaussian region, when in a highly extended state. This implies that the γ term must be temperature dependent. In order to clarify this problem, we have determined a W function for isoprene rubber that is highly stretched from the measured results by the strip-biaxial extension method. Then we have the conclusion that the W function in the highly extended state is not temperature dependent, because the temperature dependence of ∂W/∂I1 becomes very small for the extension ratio greater than 6.5(I1=43).