Copolyamides of poly(terephthaloyl hexylenediamine) synthesis: a comparative study of mechanical and thermal properties

Semi-aromatic polyamides have excellent comprehensive properties and can effectively adjust thermodynamic properties through monomer composition and ratio to meet different application requirements. Therefore, in this study, two copolyamides (PA6T/66 and PA6T/610) were synthesized by one-pot method and their thermal and mechanical properties were subsequently analyzed and compared. Firstly, the chemical compositions and microstructures of the two copolyamides were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectroscopy (¹H NMR), wide-field X-ray diffraction (XRD) and polarized ophthalmic microscopy (POM), and the viscosities [η] of the specimens were tested. Secondly, the heat resistance of the two copolyamides was analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Subsequently, the mechanical strength of the two copolyamides was evaluated. The FTIR, NMR and XRD results show that the molecular structure and crystal morphology of the two copolyamides are highly similar, which may prove the success of the target products. The TG results show that the heat resistance of the two copolyamides is very good, with the extrapolated initial decomposition temperature above 430 °C, and PA6T/66 has better heat resistance. The DSC results show that PA6T/66 has a higher melting and glass transition temperature. The mechanical test results show that PA6T/66 has greater tensile and flexural strengths of 70 MPa and 110 MPa, respectively, while PA6T/610 has better impact toughness. The above comparative results can be extended to determine the differences in performance between long-chain and short-chain polyamides, which can provide a reference for future related research.

Graphical abstract