A flame-retardant phosphate and cyclotriphosphazene-containing epoxy resin: Synthesis and properties

A novel flame-retardant epoxy resin, (4-diethoxyphosphoryloxyphenoxy)(4-glycidoxyphenoxy)cyclotriphosphazene (PPCTP), was prepared by the reaction of epichlorohydrin with (4-diethoxyphosphoryloxyphenoxy) (4-hydroxyphenoxy) cyclotriphosphazene and was characterized by Fourier transform infrared, P-31 NMR, and H-1 NMR analyses. The epoxy resin was further cured with diamine curing agents, 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenylsulfone (DDS), dicyanodiamide (DICY), and 3,4'-oxydianiline (ODA), to obtain the corresponding epoxy polymers. The curing reactions of the PPCTP resin with the diamines were studied by differential scanning calorimetry. The reactivities of the four curing agents toward PPCTP were in the following order: DDM > ODA > DICY > DDS. In addition, the thermal properties of the cured epoxy polymers were studied by thermogravimetric analysis, and the flame retardancies were estimated by measurement of the limiting oxygen index (LOI). Compared to a corresponding Epon 828-based epoxy polymer, the PPCTP-based epoxy polymers showed lower weight-loss temperatures, higher char yields, and higher LOI values, indicating that the epoxy resin prepared could be useful as a flame retardant. (C) 2000 John Wiley & Sons, Inc.