Eutectic melting behavior of polyamide 10,T-co-6,T and 12,T-co-6,T copolyterephthalamides

Semi-aromatic polyterephthalamides 10,T and 12,T were synthesized with 0–60 wt-% PA-6,T comonomer by a melt polycondensation process. Molecular weights of the copolymers ranged from 12,000 to 27,000 g/mol and all produced tough melt-pressed films. The substituted aromatic carbon of the 13C NMR spectra revealed that comonomer sequences are statistical; e.g., 50:50 wt-% PA-12,T-co-6,T copolymer had 12,T-12,T:12,T-6,T:6,T-6,T sequence ratios of approximately 1:2:1. Copolymers of both PA-10,T and 12,T exhibited a eutectic melting point at 30 wt-% PA-6,T, with melting points decreasing linearly from 315 and 292 °C to minima of 280 and 272 °C, respectively. Melting enthalpies showed similar minima at ca. 35 wt-% PA-6,T. WAXD and DMA were used to further characterize the eutectic behavior, and a comprehensive analysis of PA-6,T copolymer melting behavior is given.