Wood Modification Effects on Weathering of HDPE-Based Wood Plastic Composites

The effects of weathering on the constituents of wood and polymer matrix behavior in wood plastic composites (WPCs) were investigated. WPCs were produced from pine, extractives-free pine, and pine holocellulose fibers (60%) together with HDPE (40%). These composites were subjected to xenon-arc accelerated and outside weathering for a total of 1200 h and 120 days, respectively. The color and chemical changes that occurred on the surface of the WPCs were analyzed using a set of analytical techniques. For pine and extractive-free pine filled composites, the results showed that the total color change, lightness, and oxidation increased, while the lignin content decreased. In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) of extracted HDPE decreased with an increase in exposure time of the composites. However, HDPE crystallinity increased with longer exposure time. Lightness of holocellulose-based WPC changed the least while the change in its HDPE crystallinity was not significant compared to the other composite types. Therefore, holocellulose-based WPC may be preferred for applications where color stability is of high priority.