Thermal behaviour of bis-benzoxazines derived from renewable feed stock 'vanillin'

Several bis-benzoxazine monomers (Va-BBz)s were synthesized using a naturally occurring phenol: vanillin, different diamines such as ethylene diamine (EDA), diaminodiphenyl sulphone (DDS), diaminodiphenyl ether (DDE), diaminodiphenyl methane (DDM) and 2,2′-bis [4-(4-aminophenoxy)phenyl] propane (BAPP) and paraformaldehyde. The structure of the bis-benzoxazine monomers was characterized by FT-IR, 1H and 13C NMR. The effect of structure on curing behaviour and thermal properties was evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The poly(bis-benzoxazine)s derived from vanillin had high Tg (202-255 °C), high char yield (52-76%) and excellent thermal stability due to highly cross-linked nature of the polymer. Adhesive strength of cured resins (i.e. poly(Va-BBz)s) were also evaluated at 200 °C.