短時間で消滅する応力緩和挙動

概要

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Stress relaxation behavior of raw rubbers in a Mooney viscometer were investigated for a relatively short time region by using a photo-recording method.It was found for each rubber species that there exists a fast and a slow relaxing mechanisms in a system and their relaxation curves superpose linearly upon each other.Thus we haveML*=f1+f2 (1)Here ML* denotes the measured stress in Mooney unit, and f1 and f2 represent the stresses corresponding to the fast and the slow relaxing mechanisms, respectively.The time dependence of f1 could be approximated by the equation;f1=YLe-t*/τ* (2)irrespective of the species of rubber. Here YL and τ* are the constants independent of time t*.The value of τ* at 100°C appeared to be less than few seconds for each rubber.The stress due to the slow relaxing mechanism, f2, has the following features in its time dependence.f2(t*=0)=ML-YL, (3)f2(t*≅1min)=AL•t*-/2 (3)f(t=∞)=0, (3)where ML is the value of measured stress at t*=0 and AL is a constant independent of t*.The molecular weight, the temperature and the filler content dependences on τ* were found to be the same as those of YL for SBR samples.
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