Novel Combination of Vinyl Benzoxazine and Its Copolymerizable Diluent with Outstanding Processability for Preparing a Bio-Based Thermoset
Zizhao Qian, Yujia Lou, Qing Li, Lujie Wang, Feiya Fu, Xiangdong Liu
Abstract
The application of polybenzoxazine resin still remains a puzzling problem in processability due to the high melting temperature of benzoxazine. Here, a bio-based reactive diluent, 4-vinyl guaiacol acetate (AC4VG), and a bio-based benzoxazine monomer, 4VG-fu, were synthesized using the diluent-based strategy for improving the poor processability of benzoxazine. 4VG-fu and AC4VG show good miscibility, and their mixture solutions exhibit a very low viscosity. When the mixtures are heated, free radical copolymerization of 4VG-fu and AC4VG takes place at a low temperature range (120–140 °C), and ring-opening polymerization of the benzoxazine groups pendant to the copolymer chains occurs at a higher temperature range (140–220 °C). The last polymerization induces microphase separation in the cured resin, and the AC4VG/4VG-fu molar ratio exerts an important effect on the degree. The AC4VG/4VG-fu solutions also show good suitability with cotton fabrics for preparing composite materials, resulting in satisfactorily thermal and dynamic mechanical properties. These results suggest an effective strategy for improving the processability of benzoxazines, opening a way to develop fully bio-based polybenzoxazine resins with high performance.