Epoxypolymers: effect of the elastomer in the kinetics of polymerization

The polymerization kinetics of three epoxy adhesives HX-205, HX-206 and F-185 was defined by means of thermal analysis techniques (DSC and TMA). It was found that the liquid carboxy-terminated butadiene acrylonitriles (CTBN) and the solid rubber elastomer present in HX-206 and F-185 do not affect the phenomenological kinetics of the isothermal cure process by comparison with HX-205, which contains the same epoxy but no elastomer. It was also found that the isothermal (373 K) cure of these adhesives follows a two-range behaviour, i.e., the phenomelogical order of the cure kinetics is close to zero before and close to one after a "critical" time of cure. The trend of the glass transition temperature Tg vs the cure degree α for HX-206 and F-185 was always below that for HX-205. Tg did not approach the temperature of cure tc for α = 1 for elastomer-added adhesives, whereas HX-205 displayed an almost liear trend, with e.g. Tg = 87° C for α. = 85%.