Polimery 1998, No 11-12, 704
Zinc salt of mercaptobenzimidazole (MBI-Zn) as a solute in poly(diethylene glycol maleate) (polyester P-3) was found to be a thermally effective latent curing agent for low-molecular-weight epoxy resins based on bisphenol A (Epidian 5). The time of life of Epidian 5-based compositions A, В and C containing 2.79—7.14% MBI-Zn and 6.98—17.85% of poliester P-3, was found to be stable for at least 1 year at room temperature. DSC thermograms were run to study the curing process and the effect of process parameters on the temperature of glass transition of the cured compositions. The data allowed to select Composition В for further studies (Table 1). The initial curing temperature of Composition B, determined by the use of an Ares rheometer, was 173.1°C; the onset of thermal decomposition, established by differential thermogravimetry, was 310°C. The highest temperature of Glass transition, 124°C, was found to occur for Composition В cured at 180°C for 1.5 h. DMTA applied to this composition showed Tg = 121.7°C (Fig. 5). To check the usefulness of the cured Composition В for making insulation materials, transverse resistivity was measured and found to be 5.1012 W/cm (Table 4).
Keywords: zinc benzimidazomercaptide as latent curing agent for epoxy resins, temperature of glass transition, thermal resistance, curing of epoxide compositions