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

A novel flame-retardant epoxy resin, (4-diethoxyphosphoryloxyphenoxy)(4-gly cidoxyphenoxy)cyclotriphosphazene (PPCTP), was prepared by the reaction of epichlorohydrin with (4-diethoxyphosphoryloxyphenoxy) (4-hydroxyphenoxy) cy clotriphosphazene 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'-diaminodiphenylsulfo ne (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 reacti vities of the four curing agents toward PPCTP were in the following order: DDM > ODA > DICY > DDS. In addition, the thermal properties of the cured ep oxy polymers were studied by thermogravimetric analysis, and the flame reta rdancies were estimated by measurement of the limiting oxygen index (LOI). Compared to a corresponding Epon 828-based epoxy polymer, the PPCTP-based e poxy polymers showed lower weight-loss temperatures, higher char yields, an d higher LOI values, indicating that the epoxy resin prepared could be usef ul as a flame retardant. (C) 2000 John Wiley & Sons, Inc.