Tailoring thermal and thermomechanical properties of biobased blends by hybridization of difuran benzoxazine with polysiloxane-based benzoxazine and epoxy monomers

A difuran bio-based benzoxazine (SA-dfda) was synthesized by a three-stage process from difurandiamine (DFDA) and 2-hydroxybenzaldehyde with a final yield of 90%. Three copolymer systems were prepared by blending the difuran bio-resin with epoxy resin (DGEBA), conventional benzoxazine (BA-a), and polysiloxane-based benzoxazine precursor [Pr(BA-3aptms)] at different ratios. In order to study the effect of the renewable content on the main characteristics of the materials, thermal, thermomechanical, and morphological analyses were performed. The bio-based benzoxazine/epoxy systems exhibited the lowest polymerization temperature with enhanced processability. However, the incorporation of epoxy slightly decreased the mechanical properties of materials. Bio-based copolymers containing 5 wt%. of polysilsesquioxane precursor showed the highest glass transition temperatures, thermal stability, and char yields. All the copolymers exhibited good flame retardant properties as it was observed by their limiting oxygen index values (>21) and UL-94 tests (V-0 or V-1). The copolymerization of bio-based benzoxazines with different thermoset resins such as epoxy or benzoxazines can be used as a strategy to develop novel materials with tailor-made properties.