Synthesis and properties of epoxy resins containing 2-(6-oxid-6H-dibenz(c,e)(1,2) oxaphosphorin-6-yl) 1,4-benzenediol (II)

Advanced epoxy resins containing naphthalene and flame retardant moiety [tetrabromobisphenol-A (TBBA) or cyclicphosphineoxidediol] in the backbone were synthesized. Tgs of epoxy resins containing naphthalene structure are higher than that of the diglycidyl ether of bisphenol-A (DGEBA), and a Tg of 237°C was obtained when the tetrafunctional naphthalene-containing epoxy resin was used. In air, TGA of the phosphorus-containing thermosets displayed 11.5–22.2 wt% char yield at 800°C, while the TBBA-containing network was oxidatively decomposed to nearly zero residue. The efficiency of phosphorus as a flame retardant was found to be much higher than that of bromine. The combination of tetrafunctional naphthalene-containing epoxy resin with cyclic phosphine oxide diol has resulted in high Tg (239°C) and high limited oxygen index (LOI) 35.