Polyimide foams, due to the outstanding combined properties including low dielectric and thermal insulating, acoustic absorbing, high strength-to-weight ratio, cost effectiveness, etc., have been extensively used in many high-tech fields such as the aerospace, aviation, ship, energy and environmental protection, etc., in recent years. There are two types of polyimide foams, the soft one having opened-cell in structures and the rigid one having closed-cell in structures. Polyimide foams are usually produced by thermal foaming of the polyimide precursor, the molecular weight-controlled poly(amic ester) resins, which are prepared by polycondensation of aromatic dianhydride and aromatic diamines. There are obvious effects of chemical structure of the molecular weight-controlled polyimide precursor resins on mechanical and thermal properties of the polyimide foams. The molecular weights of the polyimide precursor resins also have apparent impacts on the foam densities, mechanical and thermal properties. In this paper, the progress of polyimide foams, especially the chemical structures, properties and applications, will be described.
Contents
1 Introduction
2 Soft and opened-cell polyimide foams
2.1 Development
2.2 Typical properties of soft and opened-cell polyimide foams
2.3 Applications of soft and opened-cell polyimide foams
3 Rigid and closed-cell polyimide foams
3.1 Preparation methods
3.2 Relationship of heat treatment temperature of precursor resin and foam structure
3.3 Relationship of main chain structure of resin and foam properties
4 Conclusion