Thermochemical recycling of waste glass fiber-reinforced polymers: A research based on experiments and quantum chemical calculations

The large-scale recycling and resource utilization of waste glass fiber-reinforced polymers (GFRPs) represents a critical challenge constraining the sustainable development of the composite materials industry. In this study, common waste GFRPs, specifically retired wind turbine blades (WTBs), were systematically investigated to elucidate their thermochemical conversion mechanisms and glass fiber regeneration technologies. This approach effectively resolves the existing bottlenecks of low pyrolysis efficiency and unclear reaction mechanisms in current thermal decomposition approaches. Through experimental analysis and density functional theory (DFT) calculations, this study reveals the degradation characteristics of retired WTBs: weight loss occurs between 290 and 500°C with an average apparent activation energy of approximately 170 kJ·mol⁻¹ . A synergistic pyrolysis-oxidation process was developed, achieving 89.5 % pyrolysis efficiency under optimal parameters (pyrolysis temperature: 500°C, pyrolysis time: 80 min, carrier gas flow rate: 50 mL·min⁻¹). Surface-clean glass fibers were successfully obtained via subsequent oxidative treatment (500°C for 80 min), achieving an organic component removal efficiency exceeding 98 %. Mechanistic studies demonstrate that epoxy resin pyrolysis follows a free radical-dominated degradation pathway: initial homolytic cleavage of C-O bonds generates various radical intermediates, which subsequently recombine to form characteristic products including bisphenol A, ethylene oxide, propylene oxide, and propylene. Notably, the presence of glass fibers (SiO₂) significantly reduces C-O bond orders, thereby accelerating resin matrix dissociation. This research provides both theoretical foundations and technical pathways for GFRPs valorization, demonstrating substantial industrial application potential.