Effect of Fiber Orientation Angle on Thermal Degradation and Ablative Properties of Short-Fiber Reinforced EPDM/NBR Rubber Composites

A series of short aramid fibers reinforced ethylene-propylene-diene terpolymer (EPDM)/acrylonitrile-buta-diene rubber (NBR) composites with designed fiber orientation angle (beta) between the short fibers orientation and the ablative surface have been prepared in this work. The influence of beta on the thermal degradation and ablation resistance properties of the composites under the oxyacetylene flame is carefully discussed. With the increasing of beta, the porosity of the char layer is reduced, whereas its hardness is improved. As a result, the pyrolysis rate (R-p) and the carbonization rate (R-c) are accelerated since the thermal conductivity of the char layer is enlarged after the composites were carbonized. The acceleration of the thermal degradation results in an increasing mass loss during the pyrolysis reaction. However, the erosion rate (R-L), mainly caused by the mechanical ablation of the high speed heat flux, is reduced gradually as beta increases due to the improved hardness of the char layer. Dominated by the two kinds of ablation methods oppositely as beta increases, the mass loss rates (R-m) decreases firstly and then increases gradually. POLYM. COMPOS., 31:1223-1231, 2010. (C) 2009 Society of Plastics Engineers