Rheology and thermal behavior of polyamide reinforced with alumina whiskers

Alumina whiskers were melt-mixed with polyamide 12 to obtain new composites with high performance properties and similar processability of neat polyamide. Three kinds of alumina whiskers were used to prepare composites (purified fibers, ribbon-shaped fibers and silica-coated fibers). The rheology, morphology and thermal behavior of composites were evaluated as function of the type of whisker and its amount in the samples. In terms of rheological properties, modulus and viscosity were enhanced as function of the amount of filler added. Good dispersion of alumina whiskers in PA12 and an optimal filler-matrix interface were observed in morphological tests independently of the kind of fiber used. Studies on crystallization behavior indicated the nucleation action of whiskers, although the most important changes in crystalline state of PA12 were observed with ribbon-shaped and silica-coated fibers. Whiskers improved significantly the thermal stability of polyamide. But kinetics of degradation process studied using Coats-Redfern method indicates that the best behavior wasobtained principally with ribbon-shaped and silica-coated whiskers. POLYM. COMPOS., 2012. (C) 2012 Society of Plastics Engineers