Radiation Technology in Polymer Waste Recycling and Upcycling: Mechanisms, Applications, and Prospects

Polymer waste represents a persistent environmental challenge, as conventional recycling methods often yield low-quality products and remain energy-intensive. Ionizing radiation, applied through gamma rays, electron beams, or X-rays, offers an alternative pathway for reprocessing and upcycling polymers. Radiation induces free radical formation, leading to two competing molecular transformations: chain scission, which lowers molecular weight and improves reprocessability, and cross-linking, which enhances mechanical strength and thermal stability. The outcome depends strongly on absorbed dose, dose rate, and irradiation conditions. Beyond molecular restructuring, irradiation can modify surface charge and polarity, enabling more effective sorting of mixed polymer streams. Reported applications include enhanced durability in rubber and polyethylene, improvements in food packaging films, and the production of wood–plastic composites with higher performance and market value. Comparative analyses indicate that, under optimized conditions, radiation-assisted recycling can match or surpass certain chemical methods in efficiency while delivering upcycled materials with extended service life. Current barriers include facility safety requirements, uniform treatment of heterogeneous waste, and integration into industrial recycling infrastructures. Future progress depends on pilot-scale demonstrations, dose–response optimization for common polymers, and comprehensive life-cycle assessments. These developments position radiation processing as a viable contribution to sustainable polymer waste management and the circular economy.