Degradation behaviour of natural rubber-aluminium powder composites: effect of heat, ozone and high energy radiation

Properties such as resistance towards heat, ozone and gamma radiation and flame resistance of aluminium powder filled natural rubber composites were studied. Aluminium powder filled natural rubber composites showed better retention of mechanical properties after thermal ageing compared to other fillers like HAF, GPF, silica and acetylene black. Tensile strength of natural rubber (NR)-aluminium powder vulcanizates increased slightly after ageing for 7 days at 70 degreesC due to the slow and continued crosslinking, but on prolonged ageing, chain scission predominated, which decreased the tensile strength. These composites also have better resistance towards ozone exposure. The cracks generated due to ozone exposure are small and discontinuous in aluminium powder filled vulcanizates, whereas the cracks are deeper, wider and continuous for other filler incorporated samples. Effects of various bonding agents namely hexamethylene tetramine-resorcinol system (HR), bis [3-(triethoxysilyl) propyl] tetrasulfide (Si-69), cobalt naphthenate (CoN) and toluene diisocyanate (TDI), on the ageing characteristics of natural rubber-aluminium powder composites were studied and it was found that these composites have better resistance towards heat, ozone, and gamma irradiation. (C) 2002 Elsevier Science Ltd. All rights reserved.