Outdoor natural weathering of bamboo flour/polypropylene foamed composites

Abstract

Color and physico-mechanical properties change from 10 months of natural outdoor weathering for injection molded bamboo flour (BF)/polypropylene (PP) foamed composites were investigated. The composite surface morphology, before and after exposure, was observed by using environmental scanning electron microscopy (ESEM). Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the chemical structures. Natural weathering was shown to cause more discoloration and surface deterioration, while the physico-mechanical properties, rheological behavior, and thermal stability were less negatively affected for composites with higher BF amount ranging from 0 to 35 wt%. The rheological behavior results indicated decreases in the storage and loss moduli and the complex viscosity of weathered composites. Crossover frequency was found to increase and the average molecular weight decreased. The initial thermal decomposition temperature declined in foamed PP by 25℃ and in 35% BF/PP foamed composite by 6℃, indicating a slight decline in thermal stability, as shown by thermogravimetric (TG) analysis. Photodegradation, photooxidation, and matrices chain scission in the composites were confirmed by FTIR and XPS analyses.