Upon continuous stress relaxation of the filled silicone rubber

especially the vulcani-zate filled with octamethylcyclotetrasiloxane-modified silica at 260-300℃

the relative stress decreases first to a minimum and then increases

proportionally with time up to a certain limit. The change can be described approximately by the formula:f(t)/f(0) - A1e-K1e + A2e-K2t + k3t + A3Here the rate constant k2 is ascribed to the degradation of the rubber matrix

k3 to the cros-slinking of the stretched chains

k2 to the cleavage of the linkage connected with filler.