Fig. 3. (a) The FTIR spectra of original epoxy resin and reclaimed oligomer after treating in 0.35 M TBD–EG solutions with solid content of 5 wt%. (b) The FTIR spectra showing the ester vibration (v_{C O} = 1730 cm⁻¹) of original and recycled oligomer after treating in 0.35 M TBD–EG solutions with solid content of 5 wt% and 15 wt%, respectively.