Examining the influence of bisphenol A on the polymerisation and network properties of an aromatic benzoxazine

•First report of copolymers formed from benzoxazines and bisphenol A.•Very good agreement between simulation and empirical thermal data.•Spectral suggests different cured polymer network as the BPA content increases.•Only 5 wt % bisphenol A significantly reduces onset of cure reaction and gel time.

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 °C to 215 °C), with a small penalty in glass transition temperature (reduction of 15 K), but similar thermal stability (onset of degradation = 283 °C, char yield = 26%). With higher concentrations of bisphenol A (e.g. 25 wt %), a significantly more reactive blend is produced (exothermic peak maximum = 192 °C), but with a significantly lower thermal stability (onset of degradation = 265 °C, char yield = 22%) and glass transition temperature (128 °C). 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.

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