High performance green composite from vanillin-based benzoxazine containing phthalonitrile and silane surface modified basalt fibers

Benzoxazine containing phthalonitrile, as one of the most advanced high performance thermosetting resin, has gained a lot of attention in the last decades. Indeed, the combination of the thermally activated ring-opening polymerization of the benzoxazine and the cyano addition reaction of the phthalonitrile allows the development of robust polymeric networks. Following this path, a renewable natural resource, vanillin, was used to develop a new benzoxazine containing phthalonitrile thermosetting system. The newly developed monomers present the advantage of a simple synthesis process along with an autocatalytic polymerization mechanism. The molecular structures of the synthesized monomers were characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (H-1 NMR). The curing behavior was assessed by differential scanning calorimetry (DSC). The newly developed monomers were then reinforced with a silane surface modified basalt fibers (BFs) allowing the preparation of a high performance green composite. The silane surface modification of the BFs was confirmed by FTIR and thermogravimetric analysis (TGA). The tensile and bending tests highlighted the remarkable mechanical properties of the developed green composite. Finally, the scanning electron microscopy (SEM) was used to study the mechanism of stress transfer between the matrix and the fillers. Overall, the developed green composite can be seen as a promising substitute to composites made from glass fibers.