Thermo-Oxidative Stability of Polyimide Composite for Aerospace Applications

摘要

Polyimides are increasingly being used in high-temperature structural composites for airframe and engine applications. A basic understanding of the structure-property relationship of polyimides will enable the intelligent selection and formulation of thermally stable matrices. Our approach aims at developing a understanding of the influence of polymer chemistry on composite stability by conducting novel polymer modifications and formulations to provide different polymer structures to minimize thermo-oxidative degradation of polyimides. We showed that the molecular weights of the prepolymers strongly influence the network structures of the polyimide, and the entrapment of unreacted prepolymer molecules in the polymer network will decrease the thermal stability. We also demonstrated that the network structures of bismaleimides can be modified by inserting bulky substituents around the amic linkages. However, thermo-oxidative stability is not improved because of the tendency for the substituents to undergo scission.