For the assembly of high-voltage devices such as transformers and generators, insulating adhesives based on epoxy resins are frequently used. In this study, adhesives based on bisphenol A diglycidylether BADGE and four model amine hardeners, namely diethylenetriamine DETA, 1-(2-aminoethylamino)-2-propanol AEAP, isophorone diamine IPD, and m-xylylenediamine mXD, were investigated in order to understand the adhesion behavior between the epoxy resin and the cellulose-based transformer board (for use in high-voltage applications) as well as the curing of the resin. BADGE/DETA and BADGE/AEAP resins, which were cured at 60 °C / 2 h, had comparatively high surface energies. After curing at 150 °C for 4 h, they had a similar surface energy like all other resins after curing, namely in the range from 44-49 mN●m-1. The isoelectric points of BADGE/DETA and BADGE/AEAP after curing at 60 °C / 2 h were significantly higher than that of the other two resins, which suggested a higher content of residual amine functionality at the surface. All resins cured at 150 °C had similar isoelectric points (Figure 1). The curing degrees of epoxy resins at a heating rate of 10 K/min (Figure 1) showed that BADGE reacted most quickly with AEAP due to the autocatalytic effect of the hydroxy group. The system BADGE/IPD cured most slowly; complete curing could only be reached at high temperatures due to steric hindrance of the cyclohexane ring. The glass–transition temperatures Tg were determined at different curing temperatures (60-160 °C / 1 h): The systems BADGE/DETA, BADGE/mXD and BADGE/IPD needed to be cured at 160 °C / 1 h to reach the maximal curing degree; BAGDE/AEAP was completely cured at 120 °C / 1 h. Completely cured BADGE/AEAP had a Tg of only 75 °C due to the lower cross-link density (hydroxy group).

Curing behavior & surface characterization of BADGE-based epoxy resins

251st National Meeting (2016)

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