Curing of epoxy resins with 1-[di(2-chloroethoxyphosphinyl) methyl]-2,4-and -2,6-diaminobenzene

Abstract

Fire-resistant compositions were prepared using 1-[di(2-chloroethoxyphosphinyl)methyl]-2,4- and -2,6-diaminobenzene (DCEPD) as a curing agent for typical epoxy resins such as EPON 828 (Shell), XD 7342 (Dow), and MY 720 (Ciba Geigy). In addition, compositions of these three epoxy resins with common curing agents such as m-phenylenediamine (MPD) or 4,4′-diaminodiphenyl-sulfone (DDS) were studied to compare their reactions with those of DCEPD. The reactivity of the three curing agents toward the epoxy resins, measured by differential scanning calorimetry (DSC), was of the order MPD > DCEPD > DDS. The relatively lower reactivity of DCEPD toward epoxy resins was attributed to electronic effects. It was shown that the heat of polymerization (ΔHpol) increases with increasing epoxy functionality of the resin. The polymers obtained were characterized by DSC, thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and Fourier-transform infrared (FT-IR). The polymers of DCEPD showed a relatively lower polymer decomposition temperature (PDT) and a higher char yield than the polymers of the common curing agents. Furthermore, it was shown that the thermal characteristics of the compositions were dependent upon the ratio of the reactants. The fire resistance of the polymers was evaluated by determining their limiting oxygen index (LOI) value. The DCEPD polymers, especially those with polyfunctional epoxy resins, showed a significantly higher fire resistance as compared with those polymers of common curing agents.