Sustainable end-of-life strategies for thermoset-based fiber-reinforced composites: advances in recycling and upcycling

Thermoset and fiber-reinforced composites (FRCs) are widely adopted for their exceptional mechanical strength, thermal resistance, and chemical stability that have demonstrated versatile applications across aerospace, automotive, marine, and sport products. Nevertheless, the ever-growing demand of these durable materials comes with an excessive volume of end-of-life waste that are difficult to process using conventional recycling methods. This review summarizes today’s strategies for value retrieval from thermoset and FRC waste including mechanical recycling, fragmentation, thermal treatment, chemical method, vitrimer-based reprocessing, and biological approach. It also presents a comprehensive comparison of their signature mechanisms, technical advantages and limitations, and qualities of the recovered products. The evaluation involves experimental studies conducted worldwide to date, systematically outlining their processing conditions, methodologies and results with particular attention to the characteristics of the recyclates. Beyond technical features and laboratory-metrics, this work uniquely incorporates an analysis of the technology readiness level and the industrial scalability for each method. Via identifying a number of engineering and economic barriers, the most viable routes for effective transitioning from research prototypes to mass industrial operations are thereby highlighted.