Study Of Reactive Diluent Method For Preparation Of Polybenzoxazine Composites And Its Processability

Almost all benzoxazine monomers have high melting point and high viscosity,leading to a very poor processability and limited applications.Inspired by the polymerizable diluent concept that had been applied in unsaturated polyester products,this work attempts to solving the problems of poor fluidity and processability of benzoxazine monomer.We first prepare4-vinylguaiacol(4VG)from ferulic acid via a decarboxylation reaction and synthesize a conjugated double bond benzoxazine monomer(VBZ)together with furfurylamine and paraformaldehyde by a solventless method.DSC and FTIR results show that the conjugated double bond in the benzoxazine monomer has very high reactivity.When the VBZ monomer was diluted by styrene(St)or methyl methacrylate(MMA),the resulting mixture solution shows an extremely low viscosity(<2 mPa·s).After gradually heated at 95~220℃,DMA and SEM analyses confirm the cured resin has certain phase separation,and its T_g is higher than 160℃.When the mixture solution was used to composite with cotton fabric,the fiber reinforced composite exhibits excellent tensile strength of 38.6 MPa and a high T_g more than 160℃,demonstrating a wide application range for preparation of composites.We further synthesize a bio-based reactive diluent AVG via an esterification of 4VG with acetic anhydride.TGA tests show that AVG has a very low volatility(only 9%weight is lost after an evaporation at 40℃ under normal pressure for 3 h).Moreover,solubility of VBZ monomer in AVG at 45℃ is 79 g/100 g,and the viscosity is lower than<5 mPa·s.Polymerization experiments suggest that AVG has high reactivity comparable with St,and the mixture of VBZ/AVG can composite with cotton fabric as well.