Study on curing behaviors of epoxy acrylates by UV with and without aromatic component

Abstract

Two kinds of epoxy acrylates, aromatic BAGEDA (bisphenol A diglycidyl ether diacrylate) and aliphatic BDGEDA (1,4-butanediol diglycidyl ether diacrylate), were prepared from BADGE (bisphenol A diglycidyl ether) and BDDGE (1,4-butanediol diglycidyl ether) respectively by reacting with acrylic acid. Synthesis and change in functional groups were confirmed by FTIR spectra. In the studies of UV curing behaviors by Photo-DSC (differential photocalorimetry), rate constants and conversions under isothermal conditions (T cure =30-80 °C) were determined by exothermic heat flows. Thus, maximum reaction rates of BAGEDA and BDGEDA were 4.06×10-2 s-1 and 5.01×10-2 s-1 respectively. UV curing behaviors were confirmed to follow Kamal equation model. Activation energies were 23.5 kJ/mol (E a1) and 12.0 kJ/mol (E a2) for BAGEDA, and 25.0 kJ/mol (E a1) and 11.3 kJ/mol (E a2) for BDGEDA. In the UV curing reaction of BAGEDA, the maximum reaction rate constants and conversions were increased by increasing reaction temperatures (T cure ), while in that of BDGEDA those were increased until 60 °C followed by a gradual decrease above 60 °C. These phenomena were understood by Gillham’s time-temperature-transformation (TTT) diagram in which curing behavior was determined by the glass transition temperature (T g ) of cured material at each reaction temperature.