Effect of silane coupling agent on the ultraviolet weathering behavior of polylactic acid based composites

Polylactic acid (PLA) is a promising material due to its biodegradability and compatibility. However, the limited resistance to ultraviolet (UV) degradation of PLA composites hinders their use in automotive interior materials. In our previous work, we successfully prepared 3D printed filaments by combining KH550-treated micro-nano rice husk (MNRH) fibers with KH570-treated PLA, which exhibited favorable performance. This study aimed to investigate the effects of silane coupling agents, MNRH, and accelerated UV weathering time on the photodegradation behavior of 3D printed PLA-matrix composites reinforced with MNRH. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were utilized to characterize the 3D printed PLA-matrix composites. Furthermore, an exponential equation between tensile strength and UV weathering time was established, providing theoretical guidance for predicting the service life of automotive interior materials based on PLA composites. The morphological characterization experimental results indicate that with prolonged UV aging time, both PLA and RH6-KH550/KH570 composite materials transitioned from transparency to translucency. This transition can be attributed to the rupture of polylactic acid molecular chains and chemical bonds during the UV aging process. FTIR test results revealed the formation of carboxylic acid in the composite, and the reduction of C=O absorption intensity indicated that MNRH and silane coupling agents exhibited a stabilizing effect on the UV durability of the RH6-KH550/KH570 composite. TGA and DSC results indicated that KH550 and KH570 delayed the photodegradation rate of PLA-matrix composites.