Accelerated Weathering of Recycled Polypropylene Packaging Bag Composites Reinforced with Wheat Straw Fibers

In this study, there were two kinds of recycled polypropylene (RPP) packaging bags, RPP disposable packaging bags (RPP-DB) and RPP woven bags (RPP-WB), used as matrix reinforced with wheat straw fiber (WSF). The aim of this study was to investigate the relative degradation behavior of WSF/RPP composites with two RPP matrices under weathering conditions. The RPP packaging bags were blended with WSF by a two-roll mill mixer and then molded by a compression molding machine. The effects of accelerated weathering on the surface morphology, surface color, surface chemistry, thermal properties, and mechanical properties were evaluated after distinct periods; the total time of exposure of the composites in a QUV-accelerated weathering tester was 1,200 hours. The weathering degradation process of WS/RPP-DB was gradual from surface to interior, whereas the internal collapse aggravated the performance reduction of WS/RPP-WB. The weathering resulted in significant discoloration. The photobleaching of WS/RPP-DB was faster than of WS/RPP-WB. The Fourier transform infrared spectrum suggested that the color change was closely related to the formation of carbonyl groups and degradation of lignin. After weathering, the thermal properties of WS/RPP-DB and WS/RPP-WB were both decreased. The flexural strength and modulus of WS/RPP strongly decreased with exposure time and was related to the surface crack of composites. The utilization of RPP packaging bags as matrix could be a good candidate of wood plastic composites for applications in the future.