Abstract

The experimental results on the abnormal melting of crystallized raw rubber by Wood and Bekkedahl are studied theoretically. The effect can be explained by the fact that the relaxation time for the thermal expansion of crystalline particles differs from that of amorphous particles. At the point where the melting begins, the time interval of observation becomes comparable to the relaxation time of amorphous particles. The point becomes higher as the time rate of heating increases, and also as the relaxation time itself becomes larger. The point at which fusion is complete is determined by the relaxation times of the amorphous and crystallized states, heating rate, and previous history. This effect becomes large at a suitable heating rate, and is larger in natural rubber than in vulcanized rubber.