Development of high-performance and sustainable polylactic acid/recycled polyolefin blends: Regulation of functionalized polyolefin content and performance optimization.

With the increasing severity of the "white pollution" problem caused by the excessive use of plastic products, the application of biodegradable materials and the recycling of plastic waste can help alleviate environmental burdens. In this study, a series of polylactic acid/functionalized recycled polyolefin blends (PLA/(R-LLDPE/POE)-g-(GMA-co-St), abbreviated as PLA/RPGS) were prepared via free-radical melt grafting. The effects of RPGS content on the crystallinity, rheological behavior, optical properties, thermal and mechanical properties, as well as the microstructure of the PLA/RPGS blends were systematically investigated. The results indicate that the prepared RPGS exhibits excellent toughening effects on PLA resin. The introduction of glycidyl methacrylate (GMA) and styrene (St) significantly enhances the compatibility between PLA and recycled LLDPE/POE (hereinafter referred to as RP), thereby markedly improving the thermal performance and flexibility of the PLA/RPGS blends while maintaining excellent optical properties. With increasing RPGS content, the entanglement within the blend system becomes more compact, resulting in gradual increases in G', G", and η, while the thermal stability first improves and then tends to stabilize. A more complex three-dimensional network crosslinked structure is formed within the blend system, which restricts the mobility of PLA chains, leading to a gradual decrease in the degree of crystallinity (X) of the blends. The notched impact strength and elongation at break of the blends progressively increase, with more pronounced ductile fracture features observed on the impact fracture surfaces, indicating a transition from brittle to ductile fracture behavior. When the RPGS content reaches 20 wt%, the haze of the blend decreases to 28.3 %, while the transmittance, T, T, and Vicat softening temperature increase to 92.2 %, 339.97 °C, 368.12 °C, and 78.2 °C, respectively. At this composition, the notched impact strength and elongation at break reach 10,182.4 J/m and 231.75 %, respectively, representing the optimal overall performance of the blends.