SIMULATIONS ON THE REINFORCEMENT OF POLY(DIMETHYLSILOXANE) ELASTOMERSBY RANDOMLY DISTRIBUTED FILLER PARTICLES

Monte Carlo computer simulations were carried out on filled networks o f poly(dimethylsiloxane) (PDMS), which were modeled as composites of c rosslinked chains and randomly arranged spherical filler particles. Th e primary concern of the investigation was the effect of the excluded volume of these particles on the elastomeric properties of the polymer s. Calculations were carried out for PDMS chains with different molecu lar masses between crosslinks, and for filler particles with different sizes and at various volume percentages. Distributions of end-to-end vectors for both unfilled and filled networks were obtained using Mont e Carlo simulations based on rotational isomeric state (RIS) theory. M ore extended configurations, with a higher end-to-end distance, were o bserved for networks filled with smaller particles. The nominal stress f and the modulus or reduced nominal stress [f*] were calculated fro m the distributions of end-to-end vectors using the Mark-Curro approac h. Relatively small filler particles were found to increase the non-Ga ussian behavior and to increase the normalized moduli above the refere nce value of unity. Temperature effects on the stress were also invest igated. (C) 1996 John Wiley & Sons, Inc.