The effects of cork powder loadings on selected physicomechanical, thermal and ablative properties of ethylene propylene diene monomer (EPDM) based thermal insulations were studied in comparison to asbestos filled EPDM thermal insulation. Ethylene propylene diene monomer was compounded with other ingredients, such as fillers, process aid and curing package, and characterised for required properties. It was observed that increasing cork loading up to 33 parts per hundred parts of rubber caused an increase in hardness and tensile strength. Elongation at break, however, decreased with increasing cork percentage in the formulations. Thermal and ablation properties of the thermal insulations were studied by ballistic evaluation motors and oxyacetylene torch. Cork filled vulcanisates had more ablation and better insulative properties than asbestos filled vulcanisates. About 39% reduction in density of the thermal insulation was possible using cork filled insulation instead of asbestos filled insulations.
Ethylene-propylene diene ter-monomer (EPDM) filled with asbestos are widely used as thermal insulation in space vehicles because of its low specific gravity, low temperature flexibility, high ozone and oxygen resistant, superior thermal and ablation characteristics. However, asbestos has been banned worldwide because of its carcinogenic nature. This study was aimed to replace asbestos by environmental friendly and low specific gravity filler, cork in thermal insulation for space vehicles. Various batches of cork filled EPDM were obtained by compounding 0, 10, 20, 40, 50, 60, 70 and 100Phr (parts per hundred parts of rubber) of cork powder with EPDM in Two-roll-mill in presence of other necessary compounding ingredients. The resulted vulcanizates were characterized for mechanical, thermal and ablation performances. It was observed that cork loadings significantly enhanced tensile strength and hardness of EPDM. However, elongation at break of EPDM decreased with the increase of cork concentration. Moreover, no significant reduction in density of EPDM was obtained instead of compounding with lower specific gravity cork powder. Temperatures cures in Thermo-gravimetric analysis shifted to lower temperature with increasing of cork percentage in the formulation. Furthermore, char formation of the EPDM composites decreased with the increase of cork Phr in the composition which was the indication of degrading thermal stability of EPDM by cork powders. It can be concluded that on the basis of mechanical properties asbestos can be replaced by cork powder however, cork filled EPDM exhibited inferior thermal properties as compared to asbestos filled EPDM.
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