Study On Thermal Properties For Thermoplastic Polyimide And Modified Materials

Polyimides is an important high-performance polymers used in aircraft, microelectronics, communication fields and so on for their marked thermal-stability, excellent mechanical, electrical and radiation–resistance properties. However, many of these polyimides are insoluable and infusible, leading them impossible to process by the conventional methods, which has confined the widespread use of the polyimides. So the thermoplastic polyimides (TPI) are becoming one of the development directions. TPI preparation research has become popular project in owing to they are not only provided outstanding comprehensive properties, but also can be easily processed, with high production efficiency, and are better than thermosetting polyimides at economic effectiveness and environmental friendly. In order to improve TPI's mechanical or tribological properties, the fibers and or lubricants are filled into the resin; another way is to make TPI blend with other polymers especially for application in high-tech fileds. At present, many research works on TPI composite materials are focused on the mechanical and tribological properties, rarely on the thermal properities. But the thermal properities of TPI, such as glass transition temperature (Tg) and coefficient of thermal expansion (CTE), are considered as the important indexes as TPI is applied in industries.Based on above background, the Tg for TPI were measured in this paper, and the effects on Tg, such as molecular weight, heat treated temperature and heat treated time were also investigated. The results showed that Tg was increased with increase of the molecular weight, meanwhile the Kanig-Ueberreiter equation provided a good fit to Tg and number-average molecule weight. Due to the TPI structure feature which contained the free end group, solid therm-cyclization could be carried out at high temperature. Accordingly, the molecular weight and Tg are also increased with increase of the heat treated temperature and time.In order to extend the TPI application area especially in the rigorous...