Phosphatidylcholine toughed phenolic foam with highly improved toughness and fire safety

Abstract

Phenolic foams (PF) are pivotal materials for insulation applications but are plagued by high friability. Achieving mechanical toughening and smoke suppression without sacrificing its inherent flame retardancy advantages remains a great challenge. In this work, we demonstrate the high efficiency of phosphate- and ammonium-containing phosphatidylcholine (L) in simultaneously imparting PF with excellent mechanical toughness, flame retardancy, and smoke suppression. By employing long flexible alkyl chains, ionic group-mediated interactions, and in situ-formed nanopores, remarkable enhancements in displacement (+32.7 %) and impact toughness (+49.6 %) are achieved, where the porous structures remain intact even after mechanical tests. Notably, the addition of L does not destroy but greatly improves the thermal insulation and fire safety of PF. Upon exposure to fire, phosphate and ammonium groups degrade into abundant noncombustible gases and phosphorus species to dilute flammable gases, terminate radicals, and form intact physical protective barriers, synergistically improving fire safety. The resulting L1-PF exhibited a highly improved limiting oxygen index of 44 %, UL-94 V0 rating, heat release decrease of 27.8 %, and fire spread rate decrease of 47.7 % at a low L loading of 1 wt%. Moreover, a remarkable decrease of 53.1 % in smoke density over that of pure PF is achieved upon further increase in L, collectively revealing its high efficiency and multifunctional integration on improving toughness and fire safety. This work presents an efficient way to address the pressing issue of PF to simultaneously achieve toughness enhancement and smoke suppression without sacrificing its inherent flame retardancy.