Synthesis and characterization of copolyamides derived from novel aliphatic bio-based diamine

Novel aliphatic nylon 6 (PA6) copolyamides were produced by melt polymerization reaction of our newly synthesized aliphatic bio-based diamine monomer: N¹, N⁶-bis (4-aminobutyl) adipamide (BABA). The pertinent long-chain polyamide salt (BABA/SA) monomer was isolated as white solid, utterly characterized for the first time. The chemical structure of BABA, BABA/SA salt, and copolyamides (PA6-BABA/SA) were investigated by ¹H NMR and FTIR spectroscopy. Depending on the chemical compositions, the viscosity and molecular weight of the copolyamides were in the range of 20 275–12 652 and 2.81–2.12 dL/g. With increasing BABA/SA salt weight content in the synthesized copolyamides, their melting temperatures (T_m) and glass transition temperatures (Tg) decreased from 211.0 to 164.0 °C and 66.6 to 43.5 °C. In addition XRD results were investigated revealing all the copolyamides transferred from α-form to γ-form. Interestingly, the as-synthesized all copolyamides possess nearly similar thermal stability (T_d = 452.2–449.5 °C) as neat PA6. Mechanical testing data revealed that with increasing BABA/SA salt content, the elongation at break of copolyamides are increased (726.19–429.34%), while the tensile strength are decreased.