Improving thermal and flame retardant properties of sorbitol-based bioepoxy systems by phosphorus-based flame retardants

Abstract

Flame-retarded sorbitol-based bioepoxy resins cured with cycloaliphatic amine hardener and containing different commercially available additive-type flame retardants (FRs) have been prepared. Three different oxidation states of phosphorus, aluminium diethyl phosphinate (AlPi) (+1), phosphonate polyol (+3), ethyl ethylene glycol phosphate and ammonium polyphosphate (APP) (+5), have been studied. The effect of using melamine cyanurate with APP and AlPi has been assessed. The self-extinguishing V-0 rating according to UL-94 flammability standard tests and very good limiting oxygen index for combustion are displayed for most flame-retarded samples at 3 wt% phosphorus content. The flame retardancy effect for the additives was confirmed using cone calorimetry. The samples containing MC with APP at 3%P content showed a dramatic reduction of the total heat release by 60% and reduction of the peak of heat release rate by 70% compared to the reference epoxy matrix. The addition of these FRs together did not decrease the glass transition temperature significantly.