AbstractDynamic 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 modulusE′ slightly decreases for system G, while it increases rapidly at first and then approaches the limiting value for system M. Primary dispersion temperatureTαincreases with increasing filler concentration. With increasing particle size,Tαdecreases 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 ofTαon particle size and concentration, an equation forTαhas been proposed:documentclass{article}pagestyle{empty}begin{document}$ T_alpha = K_f ln S^ cdot $end{document}whereKfis a constant andSis the specific surface area of filler per gram of polymer. For system G,Tαcan be expressed by the above equation, irrespective of particle size and filler concentration. In the case of system M, it is suggested thatTαis affected also by orientation in addition to the surface area of t
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