Microwave-activated oxidation to replicate polyethylene plastic environmental fragmentation and contaminant release...

The environmental degradation of polyethylene (PE) plastic is commonly described as a slow fragmentation process, generated by radical oxidation induced by sunlight, followed by gradual release of additives. Here, we challenge this view by applying a microwave-activated hydrogen peroxide (MW/H₂O₂) system able to reproduce key oxidative signatures observed during polyethylene weathering and allows study of particle release and additive release. We show that micro- and nanoplastics form concurrently, driven by early oxidative embrittlement and the development of surface cracks linked to structural heterogeneity. ATR-FTIR and depth-resolved O-PTIR spectroscopy reveal pronounced chemical transformations at the PE surface (including hydroxyl, and carbonyl groups formation) that trigger crystallinity changes, plastic swelling, and enhanced susceptibility to mechanical fracture. Using multimodal chemical analysis (µ-XRF, ICP-MS), we reveal selective migration of metallic additives (Ti, Cr, Fe, Ca), with surface enrichment directly correlated to the oxidation state of PE. Correlative analysis demonstrates that additive migration is promoted by surface oxidation and microstructural weakening, with Fick law modeling yielding diffusion coefficients up to 1.4 × 10⁻¹¹ m² s⁻¹. These results provide mechanistic insight into how aged plastics act as dynamic vectors for particulate and chemical contaminants, highlighting the need to integrate additive release into environmental risk assessments.