Synthesis and properties of nylon 6 modified with various aromatic polyamides

Abstract In this study, flexible nylon 6 was reinforced by the following rigid‐chain aromatic polyamides: poly ( m ‐phenylene isophthalamide) (PmIA), poly(4,4′‐diphenylsulfone terephthalamide) (PSA), poly( p ‐diphenyloxide terephthalamide) (POA), and poly( p ‐diphenylmethane terephthalamide) (PMA). Various high‐molecular‐weight block copolyamides were synthesized by solution polymerization using p ‐aminophenylacetic acid ( p ‐APA) as a coupling agent. Their thermal properties have shown that the block copolyamides exhibit higher T g and T m and better thermal stability than those of nylon 6, especially PmIA‐modified nylon 6. The order of their thermal properties of aromatic modified nylon 6 copolyamides is PmIA > PMA > POA > PSA. Besides, the T g and T m of multiblock copolyamides are higher than those of triblock copolyamides. From the wide‐angle X‐ray diffraction pattern, it is found that the triblock copolyamides have two diffraction peaks (i.e., 2θ = 20.5 and 24°). However, the multiblock has only one at 2θ = 20°, indicating a different crystal structure for multiblock copolyamides. This can be further confirmed from scanning electron microscopy. It shows that the triblock copolyamides are a dispersed phase structure, although the multiblock copolyamides exhibit a homogeneous texture rather than an aggregated one. For the mechanical properties, it is found that the multiblock copolyamides have a more significant reinforcing effect than the triblock copolyamides. Also, the order of their physical properties of aromatic modified nylon 6 copolyamides, such as tensile strength, is PmIA > PMA > POA > PSA; but for the elongation, the order is PSA > POA > PMA > PmIA. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1031–1043, 1998