Effect of filler particle size on dynamic mechanical properties of poly(methyl methacrylate)

Dynamic mechanical properties of poly(methyl methacrylate) (PMMA) filled with mica flakes (M) or glass beads (G) were investigated as functions of particle size and filler concentration. With increasing particle size, dynamic modulus E′ slightly decreases for system G, while it increases rapidly at first and then approaches the limiting value for system M. Primary dispersion temperature T_α increases with increasing filler concentration. With increasing particle size, T_α decreases for system G but increases for system M. For the mica-filled system, the effect of particle size on the modulus can be explained in terms of orientation of the filler by comparing the experimental data with Wu's and Padawer and Beecher's predictions of the modulus. In order to explain the dependence of T_α on particle size and concentration, an equation for T_α has been proposed: where K_f is a constant and S is the specific surface area of filler per gram of polymer. For system G, T_α can be expressed by the above equation, irrespective of particle size and filler concentration. In the case of system M, it is suggested that T_α is affected also by orientation in addition to the surface area of the filler.