DYNAMIC STRESS-SOFTENING OF FILLED VULCANIZATES

Dynamic stress-softening was studied under relatively low deformation with a series of vulcanizates filled with silica and carbon blacks. Wh en strain sweeps are repeatedly applied on the samples, G' and G '' ar e substantially reduced and loss tangent and loss compliance are essen tially increased. Almost all stress softening is achieved in the first strain sweep. Upon aging at room temperature, the softening effect ca n be partially recovered. Dynamic stress softening also shows a strong dependence on temperature and frequency as well as on rubber compound ing, filler systems in particular.