Examining the Influence of Bisphenol A on the Polymerisation and Network Properties of An Aromatic Benzoxazine

A series of reactive blends, comprising a commercial benzoxazine monomer, 2,2-bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane, and bisphenol A is prepared and characterized. Thermal analysis and dynamic rheology reveal how the introduction of up to 15 wt % bisphenol A lead to a significant increase in reactivity (the exothermic peak maximum of thermal polymerization is reduced from 245 ºC to 215 ºC), with a small penalty in glass transition temperature (reduction of 15 K), but similar thermal stability (onset of degradation = 283 ºC, char yield = 26 %). With higher concentrations of bisphenol A (e.g. 25 wt %), a significantly more reactive blend is produced (exothermic peak maximum = 192 ºC), but with a significantly lower thermal stability (onset of degradation = 265 ºC, char yield = 22 %) and glass transition temperature (128 ºC). Attempts to produce a cured plaque containing 35 wt % bisphenol A were unsuccessful, due to brittleness. Molecular modelling is used to replicate successfully the glass transition temperatures (measured using thermal analysis) of a range of copolymers.