Transient effects in dynamic modulus measurement of silicone elastomers 1. zero mean strain measurements

The strain-dependent dynamic storage modulus of a poly(dimethyl-siloxane- co-methylvinyl-siloxane-co-methylphenyl-siloxane) based silicone elastomer, which is reinforced with fumed silica and crosslinked with peroxide, is investigated. The dependence of the resulting dynamic storage modulus on the duration of cycling at a particular test condition is investigated and compared to static stress relaxation measurements in the same strain range. The dynamic modulus results are shown to depend on the time of cycling at the current test conditions as well as the time of cycling at prior conditions of lower strains. The relaxation is shown to be related to the time of cycling rather than the number of cycles performed. The pattern of behavior of the relaxation of the dynamic modulus with respect to peak strain amplitude is different than that observed in a static stress relaxation test, both of which show significant nonlinear effects in strain. The observed phenomena are interpreted in terms of the role of the polymer phase on the dynamic behavior of the elastomer material.