Upcycling waste polyamide into sustainable plastics by catalyst-free and solvent-free melt polycondensation

Abstract

Polyamide 66 (PA66), a nearly non-biodegradable polymer, has caused significant environmental damage, especially through marine debris accumulation, threatening marine ecosystems and biodiversity. Current recycling methodologies universally necessitate the use of metal catalysts and involve complex recycling procedures. This study has successfully developed an innovative catalyst-free and solvent-free carboxyl-amide exchange method based on the melt polycondensation process for the upcycling of waste PA66 into a sustainable plastic. The plastic demonstrates a broad spectrum of functionalities tailored to meet the specific requirements of various fields. It also exhibits superior mechanical properties, enhanced thermal stability and closed-loop recyclability in comparison to commercial plastics. More significantly, the in-situ formation of an anhydride linkage, serving as a labile bond, confers biodegradability on the plastic without necessitating the addition of extra monomers or additional processing steps. This study employs the conventional large-scale synthesis method, which is compatible with existing industrial equipment and holds promise for extensive industrial application. Additionally, the concept of generating easily breakable bonds in-situ offers valuable insights for the design of novel degradable materials.