Synthesis of poly( p ‐diphenylmethylterephthalamide) from recycled monomers

Poly( p ‐diphenylmethylterephthalamide) or PMA was synthesized from the reaction between recycled terephthalic acid (TPA) and recycled 4,4′‐methylenedianiline (MDA) in the presence of pyridine, triphenyl phosphite, and a solubilizing‐aid agent. The reaction conditions used for this polymerization were determined from a model reaction using pure TPA and pure MDA as reactants. It was found that PMA with the highest % yield and molecular weight was obtained when the mixture of lithium chloride (LiCl) and calcium chloride (CaCl 2 ) were used as solubilizing‐aid agents with a reaction time of 4 h. Recycled TPA with 92% purity was obtained from acid hydrolysis of waste PET bottles using sulfuric acid as a catalyst at 150°C for 5 h. Recycled MDA with 99% purity was obtained from aminolysis of rigid polyurethane foam scrap using diethylenetriamine as a degrading agent at 180°C for 70 min. PMAs prepared from recycled monomers exhibited thermal properties, which were comparable to those of PMA prepared from pure monomers. However, due to a possibility of several isomers present in recycled MDA, PMAs prepared from this monomer had lower melting points and thermal decomposition temperatures than those prepared from pure MDA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3723–3729, 2003