EFFECTS OF MOLECULAR-WEIGHT OF NYLON-6 ON THE STRUCTURE AND PROPERTIES OF NYLON-6/POLY(P-PHENYLENETEREPHTHALAMIDE) MOLECULAR COMPOSITES

The effects of molecular weight of nylon 6 on the phase separation of nylon 6 in the molecular composites of nylon 6/poly(p-phenyleneterephthalamide) (PPTA) kept at 240-degrees-C and their mechanical properties related to molecular dispersity of PPTA have been studied on the coagulated and hot-pressed film. Crystallization of nylon 6 in the composites was studied by infrared spectroscopy, differential scanning calorimetry and X-ray diffraction. The crystallinity of nylon 6 was lost in the presence of PPTA when the PPTA content exceeds 50 wt% through all the range of molecular weight of nylon 6. The N-H stretching bands characteristic of PPTA and nylon 6 united to show a sharp single peak for the hot-pressed molecular composite for nylon 6 with MW = 2.6 x 10(5), indicating the interruption of aggregation of PPTA molecules. The tensile modulus and strength were monotonously increased with increasing molecular weight of nylon 6 and weight fraction of PPTA in the composites. The improved dispersity of PPTA molecules gives outstanding mechanical properties to the molecular composite. The film strength was 170 MPa and the modulus was 12 GPa for the hot-pressed composite film of 10 wt% nylon 6 using its highest molecular weight.