Abstract
The viscosity of a difunctional benzoxazine resin is reduced by use of a monofunctional benzoxazine monomer or a difunctional epoxy monomer as reactive diluents to further improve processability. With only 25 inole% reactive diluent modification, the viscosity is reduced to 20% of that of the neat resin. The influence of the monofunctional benzoxazine on the thermal and dynamic mechanical properties of the modified polybenzoxazine is examined as a function of composition. Glassy state properties, such as stiffness at room temperature, are unaffected by the incorporation of the monofunctional benzoxazine. Thermal stability of the monofunctional modified polybenzoxazine below 200°C is not significantly affected. Properties sensitive to network structure, however, are affected by the presence of the monofunctional benzoxazine. The incorporation of the monofunctional benzoxazine reduces crosslink density and produces a looser network structure, while the difunctional epoxy increases crosslink density and produces a more connected network structure. A combined composition of the monofunctional benzoxazine and difunctional epoxy with the difunctional benzoxazine is also evaluated by dynamic mechanical analysis to investigate the two opposing network structural influences.