Mechanical properties and curing kinetics of biobased benzoxazine-epoxy copolymer for dental fiber post

Biocopolymers based on vanillin/fufurylamine-biobenzoxazine (V-fa) and bioepoxy, epoxide castor oil (ECO), were prepared for fiber post application. The mechanical and thermal properties of the V-fa/ECO biocopolymers were assessed in regard to the influence of ECO contents. The addition of the ECO at amount of 20% by weight into the poly(V-fa) preserved the stiffness, the glass transition temperature and thermal stability nearly to the poly(V-fa). Dynamic differential scanning calorimetry (DSC) was used to examine the curing kinetics of the V-fa/ECO system with different heating rates. In order to determine the activation energy ( E a ), the experimental data were subjected to the isoconversional approaches, namely Flynn-Wall-Ozawa and Friedman. The V-fa/ECO monomer mixture showed averaged E a values of 105 kJ/mol and 94 kJ/mol, corresponding to typical E a of petroleum-based benzoxazine/epoxy. The results derived using the curing reaction model and the experimental data were in good agreement, demonstrating the efficacy of the Flynn-Wall-Ozawa approach for determining the curing kinetics. The simulated mechanical response to external applied loads by finite element analysis of the tooth model restored with glass fiber-reinforced V-fa/ECO biocopolymer post showed a similar stress field with that restored with the commercial glass fiber post. Therefore, the biobased benzoxazine/epoxy copolymer overcomes many of the traditional shortcomings associated with petroleum-based epoxy resins used for dental fiber post, while demonstrating excellent mechanical and thermal properties.