CRYSTALLIZATION BEHAVIOR OF CARBON-FIBER-REINFORCED POLYAMIDES .1. DYNAMIC AND ISOTHERMAL CRYSTALLIZATION

Polyamide (PA) was compounded with carbon fiber (CF) with various cont ents (0, 5, 15, 20 vol.-%) using an elastic extruder. The effect of bo th the carbon fiber contents and the compounding method on thermal beh avior and characteristics of crystallization are studied using differe ntial scanning calorimetry (DSC), scanning electron microscopy (SEM) a nd polarizing optical light microscopy (POL). Thermal investigation wa s carried out under programmed cooling and isothermal conditions. The following results were obtained: (1) The crystallization temperature b ecame higher with the increase of carbon fiber content, while the melt ing temperature and enthalpy were scarcely affected by the carbon fibe r content. (2) The compounding methods affected the thermal behavior o f composite systems. The samples that have been extruded twice have hi gher crystallization and melting temperatures as well as higher meltin g enthalpy. (3) Isothermal crystallization was observed using DSC. Fro m the rate constant k and Avrami's index n, it was found that crystall ization was accelerated by the presence of carbon fiber without changi ng the type of nucleation. (4) The polarizing micrographs showed that the nucleation of PA occurred on the surface or close to the CF.