Heat resistance index is the glass transition temperature, to meet the high temperature, the basic point is to have a high glass transition temperature. Requirements for engineering plastics can be injection molded, TG should be at 250 ℃, another high TG, will enable the processing temperature exceeds 400 ℃. This is regardless of the polymer and the processing equipment is unacceptable. Because organic polymer material begins to decompose or be cross-linked at 400 ℃ and down. Even a very low speed, it is difficult to maintain a constant production without affecting the quality of the product. In addition, in more than 400 ℃ long-term work also makes molding equipment is difficult to maintain precision.
Engineering plastics injection molding processing methods mainly because of the high efficiency of this method of processing, high precision. However, as described above, the material used to limit the temperature of receiving processing equipment can be injection-molded resin melt viscosity should be less than 10000P. If thermoforming, it would limit the breadth of the TG. In principle, as long as having a measurable TG can be hot pressing. As TG up to 360 ℃ linear polyimide can get hot less complex shape parts. As thermosetting polyimide, pressing is the main processing methods. Recent developments show that the transfer plastic film or a casting method may be able to become a major processing methods. Because in addition to high efficiency, you can also get hot parts of complex shape is difficult to meet the law.