Accelerated Ultraviolet Weathering of Recycled Polypropylene—Sawdust Composites

Abstract

Accelerated ultraviolet (UV) weathering of hot-press molded recycled polypropylene (rPP)—sawdust composites was investigated with combinative UV radiation and water spray testing to assess the durability performance. The water absorption and thickness swelling of the composites were increased after accelerated weathering. The surface of the composites underwent significant color changes (ΔE) and lightening (ΔL*) after weathering. The Young’s modulus and flexural strength were decreased after weathering. Microstructural observations revealed a decrease in interfacial bonding between the wood flour and polymer matrix with increased exposure to weathering. The crystallinity and melting temperature of the PP—wood flour composites were decreased while neat rPP showed a 6% increase in the crystallinity after weathering. The crystallinity of rPP in the control composites without maleic anhydride polypropylene (MAPP) was slightly lower than for neat rPP, while MAPP-containing composites showed an increase in the crystallinity of rPP.