Conversion-resolved inert and thermo-oxidative degradation kinetics of six Korean single post-consumer thermoplastics by multi-rate thermogravimetric analyzer

This study quantifies how atmosphere changes the thermal degradation behavior of six post-consumer thermoplastics collected in South Korea (PET, HDPE, PVC, LDPE, PP, PS). Thermogravimetric analysis (TGA/DTG) was performed from 100 to 800 °C at 5–30 °C min⁻¹ under pure N₂ & O₂ to isolate inert and oxidative pathways relevant to thermal recycling and thermo-oxidative degradation. Conversion-resolved kinetics were extracted using Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) isoconversional methods, complemented by model-fitting (Coats–Redfern) to identify effective reaction models and derive predictive parameters. A practical operator metric was added by coupling the modeled time to 90% conversion (t 90 ) with a temperature-based energy/cost proxy to compare temperature–atmosphere choices across polymers. Oxygen consistently accelerated mass loss and reduced apparent kinetic barriers. For PET, activation energy decreased from 232 to 74 kJ mol⁻¹ in N 2 and 178–95 kJ mol⁻¹ in O 2 (FWO), while PVC showed a marked reduction from 119 to 41 kJ mol⁻¹ under O₂ at higher conversion. Polyolefins and PS were predominantly described by first-order behavior (F1) across atmospheres, whereas PET and PVC exhibited clearer atmosphere-dependent shifts in effective mechanism (PET: R2/F3 in N 2 and A2 in O 2 ; PVC: F2 two-step in N 2 and F1 in O 2 ). Increasing heating rate generally shifted T max to higher temperatures, while higher operating temperatures shortened the modeled time required to achieve high conversion. From an operational perspective, higher-temperature windows generally minimized the t 90 -based energy proxy and enhanced throughput, with polymer-specific optima. Together, the conversion-resolved kinetic analysis, mechanism mapping, and t 90 -based screening metric provide polymer-specific guidance for selecting optimal thermal treatment conditions.