All-polyamide nanofibrillar composites by in situ fibrillation of aramid fibers

All-polyamide composites containing up to 30 vol% highly dispersed PPTA nanofibrils with diameters in the range 50-500 nm were prepared by melt-compounding polyamide 6,10 (PA610) with chopped poly(p-phenylene terephthalamide) (PPTA) fibers in the temperature range 260-300°C using a twin-screw extruder. Injection moldings prepared from these composites showed not only large increases in tensile strength with respect to the unmodified PA610 matrix at temperatures well below the matrix melting point but also significant increases in melt elasticity. The melt elasticity was further enhanced by high-temperature heat treatments under quiescent conditions. It is suggested that the implied interfacial reinforcement may involve transamidation, which is known to occur extensively in polyamide melts.