Fig. 1. (a) Normalized residual mass of epoxy sample in catalyst–EG solutions using different catalysts. (b) The pictures showing the dissolution solution after immersing epoxy resin in different catalyst–EG solutions at 180 °C for 30 min. (c) Normalized residual mass of epoxy sample in 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD)–ethylene glycol (EG) solution with different catalyst concentrations as a function of heating time at 180 °C (and 170 °C). (d) The dissolution rate constant derived from eqn (1)versus catalyst concentration.