Studies on thermal degradation of short melamine fibre reinforced EPDM, maleated EPDM and nitrile rubber composites

摘要

This paper reports the results of studies on the thermal and ablative properties of the vulcanizates based on EPDM, maleated EPDM and nitrile rubber reinforced with melamine fibre, one of the recent generation high performance fibres. The thermogravi-metric studies of the composites show that the presence of melamine fibre in the vulcanizates reduces the rate of decomposition and the effect is pronounced in the presence of the dry bonding system consisting of resorcinol, hexamethylene tetramine and silica. The first degradation step of the vulcanizate is controlled by the fibre, whereas the fibre as well as the matrix contributes to the second degradation step. An increase in fibre loading decreases the rate of degradation and weight loss in the second degradation step. The rate of decomposition of NBR vulcanizates is lower than those based on EPDM and maleated EPDM rubbers. The activation energy of decomposition of the vulcanizates is increased, if fibre is properly adhered to the matrix in the presence of the dry bonding system. The crosslinking system also affects the activation energy of decomposition, especially for the second degradation step. Melamine fibre causes significant reduction in the thermal erosion rate of the vulcanizates. The fibre filled composites, in the presence of the dry bonding system, display a lower thermal erosion rate compared to those containing no dry bonding system, showing that proper adhesion between the fibre and the matrix is important to achieve improved ablative properties. Among the three matrices, the vulcanizates based on nitrile rubber display the lowest thermal erosion rate.