Synthesis, characterization, thermal and flame retardant properties of novel aryl phosphinate diglycidyl ether cured with anhydride

A novel aryl phosphinate diglycidyl ether, 10-(2′,5′-diglycidyl ether phenyl)-9,10-dihydro-9-oxa-l0-phosphaphenanthrene-10-oxide (DHQEP), was synthesized. The structure of the diglycidyl ether was characterized by elemental analysis, mass, FTIR, 1H, 13C, 31P NMR spectroscopies and X-ray single crystal analysis. In addition, compositions of the diglycidyl ether with three curing agents, e.g. phthalic anhydride (PA), hexahydrophthalic anhydride (HHPA), and aryl phosphinate anhydride (DMSA), were used for making a comparison of its heat and flame retardancy with that of DER331 and DEN438. The resulting aryl phosphinate epoxy-resin composites demonstrated a higher limiting oxygen index (LOT) value as well as a higher char yield, confirming the effectiveness of aryl phosphinate epoxide as a flame retardant for epoxy resins.