Determining weathering-induced heterogeneous oxidation profiles of polyethylene, polypropylene and polystyrene using laser-induced breakdown spectroscopy

Abstract

Weathering-induced polymer degradation is typically heterogeneous which plays an integral part in fragmentation. Despite that, the current selection of techniques to investigate such heterogeneities, especially beneath the sample surface, is sparse. We introduce Laser-induced Breakdown Spectroscopy (LIBS) as an analytical tool and evaluate its performance for depth profiling. Three types of polymers were selected (polyethylene, polypropylene, and polystyrene) that were aged under controlled conditions. We demonstrate that LIBS can detect heterogeneous oxidation on the surface and inside the samples. The results reveal that different oxidation behaviors are linked to the sample's lattice structure and the subsequent formation of microcracks. This implies that LIBS is beneficial to give additional insights into the weathering and degradation behavior of environmentally relevant plastics.

Keywords: Amorphous polymers; Depth profile and surface analysis; Heterogeneous plastic degradation; Laser-induced Breakdown Spectroscopy; Semi-crystalline polymers; Weathered plastics.