Rational Design of a Cross-Linked Fully Biobased Flame Retardant for High-Efficiency Fire Safety and Multifunctional Enhancement in Polylactic Acid Composites

Developing fully biobased green flame retardants to comprehensively enhance the performance of polylactic acid (PLA) has always been a significant challenge. In this study, a novel fully biobased flame retardant, CQEA, was successfully prepared by constructing a cross-linked network using three biobased materials: chitosan, phytic acid, and quercetin. Experimental results demonstrated that incorporating 6 wt % CQEA into PLA increased the limiting oxygen index (LOI) of the composite to 26.9%, successfully meeting the UL-94 V-0 testing standard. Moreover, the peak heat release rate (pHRR) was significantly reduced from 428 to 303 kW/m2, representing a decrease of 29.3%. Additionally, CQEA not only enhanced the flame retardancy of PLA but also promoted its crystallization process and endowed the material with excellent antibacterial properties, thereby comprehensively improving the functional characteristics of PLA. This study proposed an efficient and environmentally friendly method for modifying PLA, providing a new avenue for the development of high-performance, sustainable polymer materials. Through this approach, it is possible to address both environmental concerns and the need for advanced material functionalities simultaneously.