Furfuralcahol (from furan extracted from biomass) reacted with polyphosphazene is tested as plasticising PIN FR in epoxy. Furfuralcohol has a heat-resistant oxygen heterocycle structure and a reactive hydroxyl group. In this study, it was reacted via the commercially available intermediate HCCP (hexachlorocyclo-triphosphazene) to produce a polyphosphazene (PFMP = polybis (2-furanmethanol) phosphazene) consisting of linked identical monomers (P=N)-(furfuralcohol)2. 15% PFMP in DGEBA epoxy increased LOI from 25 to 33, decreased peak heat release rate by more than 50% and enabled UL 94 V-0 (thickness not specified). The PFMP is considered to act in both solid phase, catalysing thermally stable char formation, and gas phase, by releasing PO. and PO2. radicals. PFMP also improves the mechanical performance of the epoxy, transforming brittle fracture to ductile fracture. 15% PFMP increases impact strength (+12%), tensile strength (+40%) and elongation at break (+35%).
“Biomass-derived polyphosphazene toward simultaneously enhancing the flame retardancy and mechanical properties of epoxy resins”, Y. Xiao et al., Chemosphere 311 (2023) 137058 https://doi.org/10.1016/j.chemosphere.2022.137058
Molecule of furan: Wikimedia