Aminolysis of polyethylene terephthalate waste and utilization of subsequent amido-amine as a curing agent for epoxy coatings

PurposeThe widespread use of polyethylene terephthalate (PET) in disposable products, particularly mineral water bottles, generates significant post-consumer waste, posing a major environmental challenge due to its limited biodegradability. This studdy aims to expands the potential applications of recycled PET while aligning with sustainable practices.Design/methodology/approachThis research investigates a sustainable solution through aminolysis, a chemical depolymerization process that effectively recycles PET waste into a valuable curing agent for epoxy systems. Isophoronediamine (IPDA), with its unique cycloaliphatic structure, is used as the depolymerizing agent and reaction parameters are meticulously optimized to maximize the yield of the recycled product. The oligomer obtained was then rigorously characterized using amine value determination, Fourier transform infrared spectroscopy and 1H-NMR spectroscopy to validate its structure and purity. Furthermore, the research explores the versatility of the recycled product by using it as a curing agent for both conventional diglycidyl ether of bisphenol-A (DGEBPA) and bio-based cardanol-based epoxy systems. A comprehensive evaluation of the cured coatings is conducted, comparing their mechanical, optical, chemical, thermal and anti-corrosive properties to those cured with a commercially available polyamide curing agent.FindingsThe results demonstrate that the aminolysed PET waste effectively cures both epoxy systems, exhibiting performance characteristics comparable to the conventional system.Originality/valueThis research, presents a promising approach to address the environmental concerns associated with PET waste while simultaneously contributing to the development of sustainable materials for various applications.