Nylon 6/TiO2Composites by in situ Anionic Ring-Opening Polymerization of ϵ-Caprolactam: Synthesis, Characterization, and Properties

Two series of nylon 6/TiO2 composites were obtained via anionic ring opening polymerization of ϵ-caprolactam in the presence of untreated and surface-treated TiO2 with 3-aminopropyltriethoxysilane (APTEOS) as coupling agent by the rotational molding technique. The polymerization process was carried out using a system initiator/activator based on sodium dicaprolactamato-bis(2-methoxyethoxo)aluminate and N,N′-[methylene-di(4,4′-phenylene)bis-carbamoyl]bis-ϵ-caprolactam. All tests were performed at the initial polymerization temperature of 160° ± 2°C. The influence of both untreated and treated TiO2 particle concentration on the degree of conversion (DC), intrinsic viscosity [η], weight-average molecular weight , and water absorption of pure nylon 6 and its composite materials was investigated in the range of 0.0 to 8.0 wt.% TiO2. The thermal behavior and crystalline structures of pure nylon 6 and its composites have been studied in correlation with filler concentration by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), and room temperature wide-angle X-ray diffraction (WAXD). The mechanical characteristics, including tensile and flexural properties, elongation at break, and notched Izod impact strength, of nylon 6 and its composites as a function of TiO2 filler content were investigated for all samples. Experimental results revealed that the unmodified and surface-modified TiO2 as fillers had distinct influence on the degree of conversion, weight-average molecular weight, crystallization behavior, thermal stability, mechanical properties, and water absorption of nylon 6 matrix.