Filler reinforcement of silicone rubber

Abstract Modulus and swelling measurements were made on silicone rubber samples compounded with five different fillers. The data were at variance with the predictions of the theory of modulus reinforcement by Weiss, Rehner, Smallwood, and Guth. The results, when analyzed using a modification of the kinetic theory of elasticity proposed by the author, indicate that the increase in modulus and decrease in swelling are due primarily to polymer‐filler attachments. The areas per attachment were found to be of the order of a few square angstroms and to vary with the filler. With some fillers the same area values were obtained from modulus and swelling measurements. With others, the swelling liquid apparently displaces polymer from the filler surfaces.