Characterization and curing kinetics of new benzoxazine monomer based on aromatic diamines

A new benzoxazine monomer based on aromatic diamine was synthesized. The influence of the reaction time on the bis[6-benziloxy-3,4-dihydro-2H-1,3-benzoxazinyl] diphenyl methane composition was investigated by 1H NMR, 13C NMR and GPC. Increasing of the reaction time leads to high closed ring content in the benzoxazine monomer. The polymerization behavior of the benzoxazine monomer synthesized at 6 h reaction time was further investigated by FT-IR and differential scanning calorimetry (DSC). Non-isothermal DSC at four different heating rates was performed in order to determine the kinetic parameters and kinetic models of the curing process. Kissinger and Kissinger–Akahira–Sunose methods were used to determine the kinetic parameters. The DSC curves show an overlapping of the polymerization and the degradation processes. The activation energies for the two processes were found to be 122.9 kJ/mol and 132.5 kJ/mol for polymerization and degradation processes respectively. Both reactions are found to be autocatalytic process and the predicted models fit very well the experimental data. The resulting polybenzoxazine was also characterized by TGA and DMA.

► Synthesis of a new benzoxazine monomer at different reaction times.
► Higher reaction time gives an increase of closed benzoxazine ring content.
► The polymerization behavior of the benzoxazine was studied by non-isothermal DSC.
► DSC curves show two maximum assigned to polymerization and degradation processes.
► Polymerization and degradation processes are found to be autocatalytic reactions.