Flame-retardant and tough poly(lactic acid) with well-preserved mechanical strength via reactive blending with bio-plasticizer and phosphorus derivative

With sustainable development, advanced poly(lactic acid) (PLA) with superior toughness and flame retardancy is highly demanded in various industries, but the current design strategies often fail to achieve such bioplastics. In this work, flame-retardant and tough PLA bioplastics with well-preserved thermal stability and mechanical strength and enhanced UV resistance and soil degradation are prepared by solvent-free, reactive blending of PLA, bio-based epoxidized soyabean oil (ESO) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO). With the introduction of 10.0 wt% ESO and 3.0 wt% DOPO, the resultant PLA/10E/3D bioplastic has a high tensile strength of 52.8 MPa, with 26.3 times and 67.5 % increases in elongation at break and impact strength compared to those of PLA due to the toughening effect of ESO and the rigid structure of DOPO. The superior toughness of PLA/10E/3D enables it to outperform previous flame-retardant PLA counterparts. PLA/10E/3D achieves a vertical burning (UL-94) V-0 classification and a limiting oxygen index (LOI) of 27.5 %, indicative of satisfactory flame retardancy. Compared with PLA, PLA/10E/3D maintains high thermal stability and shows significantly enhanced UV-protecting and soil degradation properties. Therefore, this work delivers a green and scalable reactive processing method to create flame-retardant, tough yet strong bioplastics with improved soil decomposition and UV resistance, which contributes to sustainable development. • The PLA/ESO/DOPO bioplastics feature significantly improved toughness. • The PLA/ESO/DOPO bioplastics maintain great thermal stability. • The PLA/ESO/DOPO bioplastics show superior UV-shielding ability. • The addition of ESO and DOPO accelerates the degradation of PLA in soil. • The PLA/ESO/DOPO bioplastics exhibits great flame retardancy.