Relationship between thermoelasticity and reinforcement in elastomers: Silica filled silicone elastomers

Increases in modulus, tensile strength, and swelling caused by reinforcing silicone rubber with silica filler were correlated with the thermoelastic parameter, fe/f. A new semiempirical equation of state, containing a generalized front factor, was derived to explain the experimental results. While the retractive force in pure gum elastomers is largely entropic in origin, reinforcement in silicone rubber-silica systems appears to arise by greatly augmenting the deformational free energy change stored in energetic modes.