Degradation-driven release of microplastics and plasticizers from typical plastics: Implications for environmental risk assessment.

Abstract

The release of microplastics (MPs) and additives during plastic aging poses potential ecological risks, but the mechanistic links between these release processes and polymer degradation remain unclear. In this study, polyethylene (PE), polylactic acid/polybutylene adipate-co-terephthalate (PLA/PBAT), and polyvinyl chloride (PVC) were subjected to ultraviolet (UV) aging to systematically investigate the evolution of molecular structure, surface morphology, and mechanical properties. The release of MPs (10-500 μm) and phthalate esters (PAEs) was subsequently quantified by laser direct infrared (LDIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS), respectively. Results revealed a general degradation pathway of chemical oxidation-structural reconstruction-mechanical failure. Photoaging-induced structural weakening, surface hardening, and material embrittlement not only promoted the generation and detachment of MPs but also facilitated PAE migration and release by increasing diffusion pathways and exposing the internal polymer matrix. The release behaviors of MPs and PAEs exhibited distinct patterns: MP release primarily resulted from matrix fragmentation and followed a power-law model (R2 > 0.99), whereas PAE release was governed by diffusion from a finite internal reservoir and was well described by a first-order kinetic model (R2 > 0.97). The three plastics showed different release preferences. PLA/PBAT and PE exhibited higher risks of MP release, while PVC presented a more prominent risk of PAE release.