Design, Preparation And Study Of Novel Meta-substituted Plyimide Molding Powders

Polyimide has been paid more and more attention because of its outstanding thermal properties and mechanical properties since these years. However, the repeated structure of imide bond in main chain and aromatic structure has led to difficulties in the actual melt processing and high cost of materials. These become the key factors which restricts the rapid development of polyimides. Main goal of develope new thermoplastic polyimides is to reduce the melting temperature (Tm) and maintain the excellent performance of polyimide at the same time. Lower Tm and lower melt viscosity of materials will making them much easier to mold. For the thermoplastic polyimide, to improve the performance of processing, structure design should come first.After studies on the relationship between properties and structures of thermoplastic polyimides, we design a new m-diamine by increasing length of main chain and introducing flexible sulfone group to reduce density of imide ring. The diamine named 4,4'-bis (3 aminophenoxy) diphenyl sulfone (m-BAPS), which has a long chain structure, was polymerized with pyromellitic dianhydride (PMDA), molding powder with several molecular weight were synthesized. Thermal properties, stability, mechanical properties and melt viscosity of the molding powders were studied by DSC, TGA, tensile, rheological studies, respectively.Finally, we designed another diamine which has longer main chain, and contained more flexible ether ketone groups. Which was then polymerized with five commercial dianhydrides, and Molding powders with same molecular weight were synthesized. The properties of molding powders such as thermal properties, stability, mechanical properties and melt viscosity were also investigated by DSC, TGA, tensile, rheological studies. The results indicated that we synthesized a class molding powders of polyimide with low glass transition temperature, low melt viscosity and the excellent performance. Some of these molding powders can be melted processed and may become important engineering materials in the future.