Modified carboxymethyl cellulose for simultaneously enhancing fire-proofing, crystallizability, UV-barrier and hydrophilicity performances of bio-based poly(L-lactic acid)

The poly(L-lactic acid) (PLA) is a biodegradable, biocompatible, and mechanically robust biological macromolecule that has been widely applied in various fields. However, the PLA is highly flammable and prone to dripping during combustion, posing potential fire safety risk. Moreover, it exhibits an extremely poor crystallizability. In this work, a halogen-free flame retardant (C-DPPC) was synthesized from a bio-based carboxymethyl cellulose (CMC), and a novel flame-retardant PLA composite (PLA/C-DPPC) was developed. The PLA/5 %C-DPPC achieved a limiting oxygen index (LOI) of 38.2 % and increased by 91.0 %, reaching the highest UL-94 vertical burning rating of V-0 with a self-extinguishing property. The peak heat release rate (pHRR), total heat release (THR), and carbon dioxide production (CO 2 P) decreased by 41.7 %, 53.7 %, and 53.6 %, respectively, demonstrating excellent flame retardancy and fire safety performance. The excellent fire-proofing effect is attributed to the condensed-phase (continuous, compact and dense char layer) and gaseous-phase (quenching effect of phosphorus–oxygen radicals on oxygen radicals) flame retardant mechanisms. In addition, the composite exhibited improved crystallization rate, significantly enhanced UV-shielding capability and hydrophilicity. This work provides a new strategy for the development of green multifunctional materials and offers a promising example for expanding the potential applications of the PLA-based composites.