Influence of glass fiber amount,natural ageing,UV ageing and aged/reprocessed ratios on mechanical,rheological and morphological properties of polycarbonate

In the current research, the influence of reprocessing for aged glass fiber reinforced polycarbonate (PC) composites having different glass fiber amount was investigated on the mechanical properties (tensile, impact, flexural), melt flow index and morphology. Samples were subjected to two environments, namely artificial accelerated aging in a QUV chamber (simulating outdoor weathering with alternating cycles of ultraviolet (UV) light and moisture at controlled elevated temperature) for up to 336 h and natural aging in Gebze (Türkiye) for up to 1 year between August 2017 and August 2018. After these aging stages, naturally and UV aged samples were ground and the ground samples were blended with virgin glass fiber reinforced PC at different ratios (25%, 50% and 75% by weight). Natural aging caused moderate reductions in tensile strength, reaching 2.61%, 7.29%, and 7.82% decreases for 10%, 20%, and 30% glass fiber reinforced composites after 12 months, respectively. Under UV aging, tensile strength remained relatively stable, whereas elongation at break decreased up to 27% depending on fiber content and exposure duration. Flexural strength decreased by up to 13.60% after natural aging, while impact strength reductions reached approximately 20% after prolonged UV exposure. Melt flow index (MFI) values increased significantly after aging and reprocessing, indicating dominant chain scission mechanisms. In particular, 20% glass fiber reinforced exhibited a 122.82% increase in MFI after 9 months of natural aging. Reprocessed aged composites showed further MFI increases and partial recovery in some mechanical properties with virgin material addition; however, the original mechanical performance could not be fully restored. SEM observations revealed increased fiber–matrix debonding, surface cracks, and interfacial gaps after aging and reprocessing. Overall, higher glass fiber contents improved the dimensional and mechanical stability of PC composites against environmental aging, while reprocessing introduced additional degradation associated with fiber shortening and matrix deterioration.