Strong, tough, and UV-resistant polylactic acid composites by incorporating doped carbon dots

The application of polylactic acid (PLA) is still restricted due to its suboptimal mechanical and thermal properties, as well as its vulnerability to oxidative degradation under ultraviolet light (UV). To enhance these properties, fluorine, nitrogen, sulfur-doped carbon dots (FNS-CDs) were fabricated in this study and further employed as nano-reinforcing materials for PLA. Here, FNS-CDs were obtained via the solvothermal method, with citric acid and 3-fluoroaniline serving as carbon, fluorine, and nitrogen sources, while dimethylsulfoxide functioned as the solvent and sulfur source. Subsequently, PLA-based composites were produced by the melt blending technique through blending FNS-CDs with PLA. With the optimal loading of FNS-CDs, the resulting PLA-based composites exhibited remarkable strength and toughness, excellent thermal stability, and efficient UV resistance. Compared with pure PLA, the tensile strength and tensile toughness of PLA-based composites containing 1.5 wt% FNS-CDs increased by 81.4 % and 147.6 % respectively, the crystallinity rose by 25.5 %, and the UV-resistance value was also significantly enhanced. This research demonstrates the considerable potential applications of doped carbon dots in the field of high performance and multi-functional polymer composites.