Polyamide 12 (PA12)/clay nanocomposites fabricated by conventional extrusion and water-assisted extrusion processes

This work aims at comparing the efficiency of three melt compounding methods for preparing polyamide 12 (PA12)/untreated clay composites. Conventional extrusion was compared with two water-assisted extrusion methods previously described in the literature and respectively involving injection of water in the polymer/clay stream or injection of aqueous clay slurry in the polymer stream. The dispersion of the clay in the composites was analyzed at the microscale and at the nanoscale using microscopy (optical and electronic) and wide angle X-ray diffraction (WAXD). The tensile properties of the composites were evaluated. The results showed that injection of aqueous clay slurry in the polymer stream was the most efficient method for preparing PA12/untreated clay composites, although clay particles remained mainly dispersed at the microscale. This method allowed for a drastic size reduction of the microparticles, accompanied by enhancements of ca. +10 % in tensile modulus and tensile strength (compared with equivalent composites obtained by conventional extrusion). The influence of the pH of the aqueous clay slurry was also investigated: neutralization of the clay slurry generated finer dispersions, probably resulting from a better pre-exfoliation of the clay in the water medium. PA12/organophilic clay composites were also prepared as control samples. When an adequate surface treatment was selected, nanoscale dispersion of the clay platelets was easily achieved. In this case, composites prepared by conventional extrusion showed overall similar properties as their equivalents prepared using injection of water in the polymer/clay stream. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1959-1974, 2013