Chitooligosaccharide-glucose Schiff composite polylactic acid with enhancement of flame retardancy, hydrophobicity,...

Bio-based plastics have emerged as the primary research focus in the development of advanced polymeric materials, attributed to their inherent sustainability. Polylactic acid (PLA) represents a sustainable biomaterial inherently characterized by flammability. To enhance the flame retardancy of PLA, a novel Schiff base flame retardant, COS-Glu, was synthesized from chitosan-oligosaccharide and glucose. Incorporation of 7 wt% COS-Glu yielded simultaneous enhancements in flame retardancy (20% peak heat release rate reduction, UL-V1, LOI 26.8%) and surface hydrophobicity (Water contact angle climbed to 98.84°). Furthermore, the E_α associated with the condensed-phase flame retardant mechanism increased by 33.4%. Combustion analysis indicated the formation of more stable and uniform carbon residues, attributed to cross-linking reactions between imino bonds and sugar chains in the COS-Glu structure. The addition of COS-Glu, reduced the seven-day degradation residual rate of the composite polylactic acid from 82% to 37% under the catalysis of protease-K. Simultaneously, the optimal material group exhibited a 5.8% reduction in tensile modulus and a 17.8% enhancement in tensile strength. This research presents the fabrication of a novel flame-retardant PLA composite, which unveils an avenue for designing entirely bio-derived flame-retardant systems tailored for sustainable polymeric materials applications.