Recent trends in recycling and reusing techniques of different plastic polymers and their composite materials

Developing recyclable polymers provides a solution to materials' end-of-life issues and also an approach to establish a circular materials economy. The current practices in the generation and disposal of synthetic polymers are largely unsustainable. As part of the solution, the development of biodegradable polymers, which constitute a class of “green polymers” according to green chemistry principles, has been intensively pursued in the past two decades. However, the degradation of such polymers in Earth's landfills typically leads to no recovery of the materials’ value, and their degradation in the Oceans could create new or unintended environmental consequences. Industrial mechanical recycling always suffers from a significant quality loss. The proposed more sustainable solution is to develop chemically recyclable polymers that not only solve the end-of-life issue of polymers, but also provide a direct approach to establish a circular materials economy. Accordingly, this critical review article captures some selected highlights of the emerging area of recyclable “green polymers” by focusing on the major progress made and the technical and environmental benefits obtained in the development of repurposing and depolymerization processes for chemical recycling of polymers at the end of their useful life.

Both environmental and economic factors have driven the development of recycling routes for the increasing amount of carbon fibre reinforced polymer (CFRP) waste generated. This paper presents a review of the current status and outlook of CFRP recycling operations, focusing on state-of-the-art fibre reclamation and re-manufacturing processes, and on the commercialisation and potential applications of recycled products. It is shown that several recycling and re-manufacturing processes are reaching a mature stage, with implementations at commercial scales in operation, production of recycled CFRPs having competitive structural performances, and demonstrator components having been manufactured. The major challenges for the sound establishment of a CFRP recycling industry and the development of markets for the recyclates are summarised; the potential for introducing recycled CFRPs in structural components is discussed, and likely promising applications are investigated.