Fiber reinforced plastics (FRP) are used for lightweight structures in aerospace and automotive industry. Mostly they are made of thermosets like epoxy, phenolic, bismaleimide and polybenzoxazine resins. Polybenzoxazines are an upcoming class of thermosets, gaining more and more interest in polymer research due to their outstanding characteristics. They offer good mechanical properties as well as chemical and thermal stability which are comparable to epoxy based systems. Furthermore, they feature long shelf life, good flame resistance with high char yields and low water absorption. In comparison to conventional phenolic resins, benzoxazines are able to polymerize without the need of initiators, with near zero shrinkage and without water release leading to a better finish quality of the manufactured parts.
High curing temperatures of typically 160 °C to 220 °C and brittleness of polybenzoxazines, however, limit the field of application. With respect to benzoxazine based FRPs, the high viscosity of neat benzoxazine monomers with more than 1 Pas at room temperature restricts the use of standard manufacturing processes.
Therefore, we present a formulation of thermo-responsive polybenzoxazines with the aim to increase the impact resistance and to reduce the curing temperature. This will be accomplished by non-covalent and covalent incorporation of partially crystalline systems into benzoxazine resins via ring opening polymerization without the need of initiators.
New benzoxazine formulations with improved properties require customized manufacturing processes suitable for high melting monomers and their thermo-responsive polymers. Thus, new manufacturing processes will be developed based on modified vacuum infusion (MVI) and resin transfer moulding (RTM) techniques.
Advances in benzoxazine chemistry and their manufacturing will provide access to FRPs in automotive and aerospace applications by fulfilling the process as well as performance requirements.