Viscoelastic Properties of Model Networks with Known Concentration of Defects

L.E. ROTH; D.A. VEGA; E.M. VALLÉS; M.A. VILLAR

Valencia, España

Simposio; IX Simposio Latinoamericano de Polímeros, SLAP04 y VII Congreso Ibero-americano de Polímeros, CIP04; 2004

Model poly(dimethylsiloxane) networks were obtained by the hydrosylilation reaction, based on the addition of hydrogen silanes from the cross-linker molecules to end vinyl groups present in the prepolymer molecules. Viscoelastic properties of the networks were found to be a function of type of defect and of both the concentration and molecular weight of either free or pendant chains. An increase in the concentration of either free or pendant chains decreases the elastic modulus due, fundamentally, to the reduction in the concentration of elastically active chains in the resulting networks. On the other hand, an increase in loss properties is observed. At low frequencies loss modulus of networks containing pendant chains is at least one order of magnitude higher than values obtained for networks with free chains with the some molecular weight. All these experimental results are in good agreement with the theoretical predictions of the tube model.