Fully bio-based benzoxazines are attractive thermosetting resins, but the limited variety of raw materials is a serious challenge for their further development. Herein, a new sustainable hyperbranched benzoxazine (HB), namely HB-Ra, was first designed and synthesized via the A₂ + B₃ method using resveratrol, paraformaldehyde and 5,5′-methylenedifurfurylamine (DFDA) derived from furfurylamine. The weight-average molecular weight (M_w) and polydispersity (PDI) of HB-Ra with good solubility were 17 000 Da and 2.26, respectively. Poly(HB-Ra) exhibited good thermal stability at high temperature at a 5% weight loss (T₅) of 374 °C and a glass transition temperature (T_g) of 348 °C. Remarkably, the ultralow coefficient of thermal expansion (CTE) for poly(HB-Ra) was only 8.4 ppm °C⁻¹. The low total heat release (THR) of 7.4 kJ g⁻¹ and heat release capacity (HRC) of 39.6 J g⁻¹ K⁻¹ suggest that poly(HB-Ra) can be used as a potential nonignitable material. Moreover, poly(HB-Ra) exhibited low dielectric constants (k) varying from 2.38 to 2.42 in the range of 2–18 GHz, which may meet the needs of high-frequency microelectronic devices. These good results indicate that this technically simple synthetic strategy is a nice choice to prepare other fully bio-based HBs.

This work studied the structural, morphological, mechanical, and thermal properties of newly designed polymeric materials using high-performance hybrid fibers to reinforce the polybenzoxazine resins. To achieve this goal, hybrid fibers consisting of chopped Kevlar and carbon fibers were subjected to a silane surface treatment, incorporated into the resin matrix in various combinations, and then isothermally cured using the compression molding technique. The mechanical performances of the prepared composites were scrutinized in terms of bending and tensile tests. By way of illustration, the composites holding 20 wt % Kevlar fibers and 20 wt % carbon fibers accomplished a bending strength and modulus of 237.35 MPa and 7.80 GPa, respectively. Additionally, the same composites recorded a tensile stress and toughness of 77 MPa and 0.27 MPa, respectively, indicating an increase of about 234% and 32.8% when compared to the pristine resin’s properties. The thermogravimetric analysis denoted an excellent thermal resistance of the reinforced hybrid composites. Fourier transform infrared spectroscopy proved that the functional groups of the as-used coupling agent were effectively grafted on the external surfaces of the reinforcing systems, and further confirmed that the chemical reaction took place between the treated fibers and the polybenzoxazine matrix, although the scanning electron microscope showed a uniform dispersion and interfacial adhesion of the fibers within the resin matrix. In fact, the incorporation of treated fibers along with their good dispersion/adhesion could explain the progressive enhancement in terms of thermal and mechanical properties that were observed in the hybrid composites.