Synthesis, Characterization, and the Potential for Closed Loop Recycling of Plant Oil-Based PA X.19 Polyamides

We report on plant oil-based linear aliphatic polyamides from 1.19-nonadecanedioic acid and aliphatic diamines of different chain lengths. Their thermal, mechanical, and rheological properties as well as the water uptake and crystalline structures were analyzed. The polyamides were synthesized with high molecular weights of 26 000 to 52 000. All polyamides showed high thermal stability with T5% of >400 °C as well as high crystallinities of ∼50%. Injection molding of the plant-oil-based polyamides was successfully performed to produce tensile test specimens. Chemical recycling of the polyamides was demonstrated by microwave-assisted hydrolysis, with a recovery of 99% for 1.19-nonadecanedioic acid. Melt polycondensation using the recovered monomer was successfully performed to synthesize recycled polyamide in similar quality, which underlines its potential for closed loop recycling.