The effect of curing temperatures on the thermal behaviour of new polybenzoxazine-modified epoxy resin

In this study, hydroxyl end functional group benzoxazine monomer (BZ-OH) was synthesized from ethanolamine, bisphenol-A and paraformaldehyde. The monomer was analysed and confirmed by Fourier transform infrared, and (¹H and ¹³C) nuclear magnetic resonance techniques, respectively. The benzoxazine (10% by weight) was incorporated into a (50:50) weight ratio of epoxy resin and its hardener. This mixture was first cured at room temperature for 24 h and then post-cured at temperatures; 90, 120, 150, 180, 200 and 220 °C, respectively. Thermal gravimetric analysis was employed to study the effect of the different curing temperatures on the thermal properties of the benzoxazine/epoxy mixture. The results showed an overall improvement in the thermal stability of the samples as the curing temperature is increased. However, the product cured at 220 °C depicted a better thermal behaviour, with a decomposition temperature in the range of 258–532 °C.