Chapter 28 - Polybenzoxazine/Fiber Composites

Abstract

Polybenzoxazines are obtained by a ring-opening reaction at elevated temperatures, and no byproducts are released, which lowers porosity in the composites. The hydrogen bonding interaction and the molecular chain rigidity of polybenzoxazines result in excellent heat-resistant and mechanical properties. The N atoms in the structures of polybenzoxazines greatly enhance their flame retardancy, making them suitable for the fabrication of flame-retardant composites. Moreover, the composites with benzoxazine resins as matrix can be used in the electrical insulation industry because of their good electrical insulation properties. Benzoxazine precursors can be dissolved in toluene, acetone, methyl ethyl ketone, and other common solvents. During the ring-opening polymerization of benzoxazine precursors, there is no volatile released and near zero shrinkage can be obtained, making this resin suitable for the fabrication of fiber-reinforced composites. At present, benzoxazine resin is used in lamination, RTM, winding, and mold pressing methods according to different requirements. Polybenzoxazine/fiber composites have a wide potential application for heat-resistant, insulating, and structural materials due to their excellent thermal, mechanical, and electrical properties. The polybenzoxazine/fiber composites have individual properties and need suitable process methods. The mechanical, thermal, and electrical properties of these composites have been evaluated comprehensively. Some polybenzoxazines have higher char yield; the composites based on polybenzoxazine can be used for ablative material such as thermal protection in rockets, strategic and tactical missile warheads, and engine nozzles.