The boron trifluoride monoethyl amine complex cured epoxy resins

The curing exotherm pattern is affected by the equivalent ratio of curing agent, boron trifluoride monoethylamine complex (BF 3 · MEA), to epoxy resin. The diglycidyl ether of 9,9‐bis(4‐hydroxyphenyl) fluorene (DGEBF) cures more slowly than the diglycidyl ether of bisphenol A (Epon 828). The glass transition temperatures ( T g 's) of BF 3 · MEA cured Epon 828 are increased with inceasing concentration of curing agent (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF 3 · MEA (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF 3 · MEA (0.0450 eq./epoxy eq.) cured Epon 828 and DGEBF are almost equivalent 43 and 44 kcal/mol, respectively. DGEBF when added to DGEBA improves the T g and char yield with the BF 3 · MEA curing system. The T g of both resin systems can be increased by longer post cure, whereas the char yield does not appear to change significantly. No ester group formation is found for the BF 3 · MEA‐cured DGEBF, although this has been previously reported for the DGEBA system. The BF 3 · MEA cure at 120°C is better than at 140°C because of vaporization and degradation of the curing agent at the higher temperature. The rapid gelation of the epoxy resin may be another reason for the lower degree of cure at high temperature.