Effects of glass bead size and content on the viscoelasticity of filled polypropylene composites

The dynamic mechanical properties of glass bead filled polypropylene (PP) c omposites have been measured over a temperature range from - 150 to 100 deg rees C and at a fixed frequency of 1 Hz, by using a dynamic mechanical anal yzer (DMA), to identify the effects of the size and content of the fillers on these properties of the composites. The results show that the flexural s torage modulus, E'(c), and loss modulus, E "(c), of the composites increase non-linearly with increasing volume fraction of glass beads, phi(f), at 25 degrees C. The dynamic moduli of the PP filled with the biggest glass bead s are higher than those of the smaller bead filled systems at the same test conditions, especially for E "(c). The influences of the filler size and c ontent on the mechanical damping of the composites is insignificant. When p hi(f) is from 5 to 15%, the glassy transition temperature of the composites slightly increases with increasing phi(f), and it reaches maximum at phi(f ) = 15%, then decreases. Also, at 25 degrees C the complex viscosity of the composites, eta(c)*, linearly increases with the increase of phi(f). and t he value of eta(c)* for the PP filled with biggest beads is higher than the other systems at the same concentration. (C) 1999 Elsevier Science Ltd. Al l rights reserved.