Synthesis of Biobased Benzoxazines Suitable for Vacuum-Assisted Resin Transfer Molding Process via Introduction of Soft Silicon Segment

A series of biobased benzoxazine oligomers suitable for vacuum-assisted resin transfer molding (RTM) were prepared from eugenol derivatives, furfurylamine, diamine, and paraformaldehyde. After the structures of these oligomers were identified by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR), their curing behaviors and processability were evaluated by differential scanning calorimetry, FT-IR, and rheological tests. Results showed that the oligomers had stable viscosity lower than 1 Pa·s in the temperature range from 60 to 190 °C, and their processing window was found to be wider than 160 °C. The cured resins exhibited excellent thermal properties (10% thermal weight loss at 406 °C and glass transition temperature greater than 110 °C), good hydrophobic performance, and low moisture absorption. The benzoxazine oligomers reported here demonstrated great potential in the fabrication of composites, especially the green composites via more efficient processes, such as RTM.