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, f e /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.