Influence of Different Environmental Factors on the Aging of Corn Straw/Polycarbonate (PPC)/Polylactic Acid (PLA) Composite Materials

This study aims to gain a deeper understanding of the effects of different environmental factors on the mechanical properties, surface morphology, and microstructure of corn straw/polycarbonate/poly(lactic acid) composite materials. Three different aging methods, namely wet heat aging, natural aging, and oxidative thermal aging, were used to investigate the effects of high temperature, humidity, and light on the mechanical properties, surface morphology, and microstructure of the composite materials. The surface morphology, chemical, thermal properties, and crystallization behavior of aged samples were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and multifunctional X-ray diffraction, respectively. Research findings reveal the impact of environmental factors as follows: First, elevated-temperature environments induce plastic degradation and activation of polymer molecular chains, significantly reducing the mechanical properties of composite materials. Specifically, the flexural and impact strengths experience reductions of 57.6 and 30.3%, respectively. Second, elevated humidity leads to the infiltration of water molecules, causing changes in the internal structure of composite materials. It, in turn, diminishes the bonding degree between fibers and plastics, induces surface cracks, and adversely affects mechanical properties. Consequently, flexural and impact strengths are reduced by 58.1 and 7.2%, respectively. Third, exposure to light triggers lignin photo-oxidation, causing the surface of composite materials to fade, △E increased by 19.28%.