Fire Retardancy of Poly(ethylene 2,5-furandicarboxylate-co-ethylene terephthalate) Regulated by Phosphinate

A flame retardant containing two phosphonate structures (DOPO–DP) was synthesized by applying diphenylphosphinic chloride and 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphazephenanthrene-10-oxide. The DOPO–DP was used to modify the flame retardancy of poly(ethylene 2,5-furandicarboxylate-co-ethylene terephthalate) containing (PEFT). DOPO–DP has a high flame-retardant efficiency in PEFT. The UL-94 V0 level is obtained by adding 7 wt % DOPO–DP into PEFT. The fire-retardant mode of action is melting away, which is induced by the plasticizing effect of DOPO–DP mainly. In addition, two chain extenders triglycidyl isocyanurate (TGIC) and 2,2′-(1,3-phenylene)-dioxazoline were applied to enhance the mechanical properties of PEFT. DOPO–DP deteriorates the mechanical properties of PEFT while coupling agents improve the bending and impact strength. While the chain expansion effect of TGIC competes with the plasticizing effect of DOPO–DP, excessive TGIC deteriorates the UL-94 rating of PEFT.