Influences of inorganic fillers on curing reactions of epoxy resins initiated with a boron trifluoride amine complex

Inorganic fillers are widely used for epoxy resins to improve mechanical and thermal properties. However, inorganic fillers may unexpectedly affect the curing reactions of such epoxy resins. In our present study, influences of inorganic fillers on the curing reactions of phenol novolac epoxy resin (EPN) initiated with boron trifluoride ethylamine complex (BF3MEA) are detailed. The gel times of epoxy resins containing alumina (Al2O3) fillers were longer than those of corresponding unfilled epoxy resins, indicating that Al2O3 fillers delayed the curing reactions of epoxy resins. Mechanisms were proposed and influences of aluminum hydroxide (Al(OH)3), silica (SiO2), and aluminum fluoride (AlF3) fillers were also described.