Search

A fully biobased waterborne flame‐retarded epoxy system was prepared using sorbitol polyglycidyl ether epoxy resin (SPE) and phytic acid (PA) as a reactive flame retardant (FR). The flame‐retardant efficiency was evaluated by comparing the reference SPE‐PA system with solventborne and waterborne SPE systems. Additional enhancement of intumescence and reduction of flammability was achieved by incorporating ammonium polyphosphate (APP) and melamine (MEL) into the SPE–PA system. PA, serving as a curing agent, contributed approximately 1% phosphorous content, resulting in an increased limiting oxygen index (LOI). UL‐94 flammability tests demonstrated improved FR properties with PA, and the addition of 2% phosphorous from APP to SPE‐PA achieved a self‐extinguishing V0 UL‐94 rating. Thermogravimetric analysis (TGA) revealed enhanced thermal stability and higher char yield with PA compared with other curing agents. Mass loss calorimetry (MLC) confirmed the superior charring effect of PA compared with other curing agents. The thermal insulation properties of the residual char were assessed by measuring the temperature on the back surface (Tb) of coated steel plates exposed to a 25 kW/m2 heat flux for 1 h. The PA sample containing 3%P of APP exhibited a Tb decrease of 130°C compared with the solventborne reference sample. Scanning electron microscopy analysis of the char morphology supported these findings, indicating the effectiveness of the intumescent FR system. Infrared spectra of the char residues and pyrolysis gaseous products were obtained to gain insights into the flame‐retardant mechanism of the different systems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A water-soluble sorbitol polyglycidyl ether (SPE) epoxy monomer was cured with a waterborne polyamine hardener to prepare a fully waterborne epoxy system. Aluminum diethyl phosphinate (AlPi) and melamine cyanurate (MC) flame retardants (FRs) were utilized to develop the flame retardancy of this epoxy matrix. The effect of loading different weights of MC with only 1%P-content from AlPi was discussed to investigate the possible cooperative effect of these two FRs. The best results were obtained at 5% MC loading with 1%P of AlPi as the self-extinguishing behavior was observed with a good limiting oxygen index (LOI). Furthermore, under forced flaming conditions in cone calorimetry measurements, the peak of heat release rate (pHRR) decreased by 27.4%, and the total heat release (THR) decreased by 14.5% compared to the reference epoxy system. This enhancement of flame retardant properties might indicate the synergistic effect between MC and AlPi in a waterborne system. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]