Thermal and electrical studies on irradiated silica-ethylene-propylene diene monomer (SiO2/EPDM) composites

Ethylene propylene diene monomer (EPDM) was mixed with a concentration of (40 phr) of three types of silica (SiO2) with different surface areas. The obtained vulcanizates were subjected to thermal properties measurements (thermal conductivity, lambda, thermal diffusivity, a, and specific heat capacity, C-p using the flash method technique in the temperature range (30-150 degrees C). The addition of polar SiO2 was found to increase the thermal diffusivity, whilst it decreases upon the addition of non-polar SiO2. Radiation sensitizer was found to decrease the value of the specific heat for all composites. The addition of EGDM as coagent increases the value of lambda for EPDM containing non-polar SiO2. Degradation is found to be the predominant process for all EPDM loaded samples at gamma-irradiation dose greater than or equal to 15 kGy. Moreover, the effective thermal conductivity was calculated using a simple model. The addition of EGDM as coagent increases the value of the dielectric constant (epsilon') for EPDM containing non-point SiO2 (type A-972) whilst, it decreases epsilon' for the other white fillers. (C) 1998 Elsevier Science Ltd All rights reserved.