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

The dynamic mechanical properties of glass bead filled polypropylene (PP) composites have been measured over a temperature range from - 150 to 100 degrees C and at a fixed frequency of 1 Hz, by using a dynamic mechanical analyzer (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 storage 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 beads 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 content on the mechanical damping of the composites is insignificant. When phi(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 the 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. All rights reserved.