Preparation of daidzein-based bio-benzoxazine/novolac thermosetting blends with low curing temperature and high thermal stability
It is well-established that the oxazine ring in benzoxazine resin generally exhibits good stability at ambient temperature, but undergoes ring-opening polymerization reactions at relatively higher temperatures. To make benzoxazine resin more practical for application, it is crucial to lower its curing temperature. In this study, novel thermosetting systems were prepared by using bio-based benzoxazine derived from daidzein (Dz-fa) blending with commercialized novolac resin. Novolac resin, which contains rich phenolic hydroxyl groups, was utilized as the curing accelerator for Dz-fa. The curing behavior of the thermosetting blends as well as the properties of the resulting thermosets was systematically investigated. The curing kinetics of the bio-based benzoxazine with novolac resin were monitored using differential scanning calorimetry and in situ FTIR spectroscopy. The thermal properties of the cured resins were assessed by thermogravimetric analysis and dynamic mechanical analysis. The flexural strength of materials is tested by universal material testing machine. These results demonstrated that employing the novolac resin effectively reduced the curing temperature of the bio-based benzoxazine without sacrificing too much in terms of the thermal stability and mechanical property. Specifically, the char yield of cured resin (Yc), the glass transition temperature ( T g ) and flexural strength of Dz-fa and novolac resin blends in the ratio of 9:1 were found to be 65.0%, 314 °C and 84.05 MPa, respectively. This study provides a practical approach to lowering the curing temperature of benzoxazine resins. The thermosets with relatively high thermal stability can be achieved through implementable process, thereby potentially reducing overall costs during the production of benzoxazine-based materials.
危险品化学品经营许可证（带存储）