It refers to a material in the heat resistance while maintaining performance available can withstand temperatures. Usually a glass transition temperature TG is represented. As a structural material, the design temperature should be in the following TG 30 ~ 50 ℃. As a non-structural materials, insulating materials, the use of temperature can be higher.
So to answer "How much of this material may be in use?" This question is quite complex This is because you intend to use long time: thousands of hours of continuous use, or require only a few minutes resistance (for example, requires the use of aircraft at a predetermined temperature tens of thousands of hours, minutes and missile capability is enough. Polymer materials currently used for aircraft structural materials at 300 ℃ long-term use is not easy. As for the missiles, it requires the use is possible at 400 ℃. In addition, and use what medium factors.
Therefore, it must explain conditions of use in order to answer this question. For questions answered temperature materials have been used in the past at certain temperature weightlessness material (or changes in other properties) extrapolation. However, for practical applications, the reliability of such data is not sufficient. Especially for important material. Such as structural materials for aircraft, the key parts of the insulation materials. The most reliable method is measurement isothermally aging, the test is carried out before the actual use temperature, to obtain the real design data.
As a class of polyimide heat-resistant molecule, the thermal decomposition and thermal oxidative decomposition of the earliest studies. The main work reports are published in the 1960s and 1970s. Thermal decomposition of soybean thermal gravimetric analysis. With a constant temperature and climate changes in laws mass of the sample was observed. In order to analyze the composition of the decomposition of gas, pyrolysis gas chromatography and mass spectrometry can be used with. But only one temperature to do a surgery is very complicated. This year's re-emergence heat - Chromatography method can give a variety of changes in the quality of the decomposition of the sample and the change in the amount of gas in a heating process, so research is a powerful means of thermal decomposition.