A triazine-based hyperbranched char-forming agent for efficient intumescent flame retardant Poly(lactic acid) composites

It still remains a challenge to address the issues of high flammability, severe dripping and toxicants emission of poly(lactic acid) (PLA) under fire conditions, restricting its widespread usage. In this work, a triazine-based hyperbranched charring agent (TBHCA) was synthesized via the polymerization of A2 + B3 type reaction, and further incorporated into PLA matrix in combination with ammonia polyphosphate (APP) for achieving fire hazard suppression. The resultant PLA/APP/TBHCA composites exhibited superior fire safety, including low heat release, reduced carbon monoxide (CO) emission and anti-dripping behavior, as proved by the results of limiting oxygen index (LOI) and cone calorimeter tests. With the incorporation of 13.33 wt% TBHCA and 6.67 wt% APP into PLA matrix, the LOI value of PLA composite reached 29% and passed UL-94 V0 rating in vertical burning test. Additionally, significant reductions in peak heat release rate (by 54.7%), peak CO production (by 60.2%) and anti-dripping performance can be acquired, resulting from the synergistic effect between the phosphoruscontaining flame retardant and triazine-based hyperbranched char-forming agent. This work provides a simple approach to the construction of phosphorus-containing and triazine-based intumescent flame retardant systems for polymeric materials.