Quantification of microplastics formed during weathering from wood-plastic composites

Accumulation of microplastics (MPs) and the potential risks that they bring causes justified concerns. Plastic-based materials are widely used in various applications. The materials are presumed to be inert and safe. However, the formation of potential MPs has introduced some doubts. Wood-plastic composites (WPCs) are among the materials suggested to be environmentally friendly. However, they may release MPs due to weathering as WPCs are widely used in outdoor applications. The objective of the study was to collect, quantify, and compare MPs' release during artificial weathering from WPCs and evaluate the effect of composition. In the study, four experimental and four commercial WPCs were analysed. Recycled polypropylene (rPP) was used as a reference. The results showed that WPCs can be a source of MPs, and that their composition significantly affects their formation. Wood particles in WPCs facilitate erosion, causing MPs to be released at a rate of 5.6 g/m2, whereas the release from rPP was 0.1 g/m2 after one month of accelerated weathering. For commercial products, MPs formation depends on the product type, with no MPs released for WPC decking but a significant release of up to 58.9 g/m2 for the flowerpot after 2 months of accelerated weathering.