Summary 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.

A fully waterborne epoxy system was prepared from waterborne sorbitol-based epoxy resin cured with an alkylated polyalkylene polyamine hardener. The flame-retardant property was accomplished by the application of different additive phosphorous flame retardants (FRs). Phosphonate polyol and ethyl ethylene glycol phosphate which are in the liquid phase, and two FRs in the form of fine-grained particles; aluminium diethyl phosphinate (AlPi), ammonium polyphosphate (APP). The flame-retardant epoxy resin blends were prepared at the same levels of phosphorus content. The results are very promising as the self-extinguishing behaviour was observed at 3%P for all the investigated FRs and at 1%P in the case of APP. Limiting oxygen index (LOI) values were practically good for all FRs and extremely improved in the case of APP. LOI was 48% for the APP sample at 3%P content. Furthermore, this blend showed the best results in the forced flaming conditions as the total heat release in cone calorimetry measurements (THR) decreased by 43% and the peak of heat release rate (pHRR) decreased by 65% with more elongated burning compared to the reference SPE matrix. The efficient solid-phase FR effect of APP was confirmed by scanning electron microscopic (SEM) and attenuated total reflection-infrared spectrometry (ATR-IR) analysis of the residual char after cone calorimetry measurements.

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