Effect of filler network on dynamic viscoelastic properties of uncured polymethylvinylsiloxanes filled with silica and carbon black

Dynamic properties of polymethylvinylsiloxane (PMVS) filled with filler-blends composed of carbon black (CB) and silica (SiO2) were investigated using an advanced rheometric expansion system. A variety of weight fraction of CB to SiO2 were 0/100, 10/90, 30/70, 50/50, 70/30, 90/10, and 100/0, and a bifunctional organsilane, bis(3-triethoxysilylpropyl)tetrasurfane, was used to facilitate the filler dispersion. The results reveal that the incorporation of CB/SiO2 filler-blends into PMVS result in a reduced Payne effect. This effect reaches a minimum when the ratio of CB/SiO2 approaches 1, and then it began to rebound with the ratio increase. Meanwhile, a characteristic Newtonian viscosity plateau appearing in low frequencies also significantly decreases, depending on the amount of CB or SiO2 added. On the basis of a simplified Fowke model, we ascribe this phenomenon to the deteriorated filler network, which is predominantly induced by the totally different surface activity between CB and SiO2. (c) 2006 Wiley Periodicals, Inc.