Viscoelastic behaviour of filled, and unfilled, EPDM elastomer

The viscoelastic behaviour of gum and a highly filled ethylene-propylene te rpolymer (automotive windowseal component) at 138 parts carbon black loadin g was investigated using a dynamic mechanical analyser over a wide range of time, temperature, strain and frequency. The tensile stress relaxation and recovery results of the gum system show time-dependent but strain-invarian t behaviour, whereas the filled system shows both strain and time dependenc e. The relaxation time spectrum of the filled system reveals nonlinear visc oelastic behaviour. The networks of carbon black formed at such a high load ing contribute significantly to the relaxation process. The 3D plot of tens ile modulus as a function of time and temperature for both the systems foll ow a similar trend, and even for short-time testing the highly filled syste m appears to be time-temperature superposable. (C) 2000 Elsevier Science B. V. All rights reserved.