What are the production processes of polyimide film
The production process of polyimide film mainly includes the following types:
1. One step method
Process: The raw materials such as dianhydride and diamine are directly polymerized in a solvent, and an appropriate amount of additives are added. Then, the reacted solution is made into a thin film through methods such as casting or extrusion, and then dried and cured to form a polyimide film
The production process of polyimide film mainly includes the following types:
1. One step method
Process: The raw materials such as dianhydride and diamine are directly polymerized in a solvent, and an appropriate amount of additives are added. Then, the reacted solution is made into a thin film through methods such as casting or extrusion, and then dried and cured to form a polyimide film.
Features: The process flow is relatively simple, the production cycle is short, and the cost is low. But high purity and reaction conditions are required for the raw materials, otherwise it is difficult to control the progress of the reaction and the performance of the products.
2. Two step method
process
Step 1: First, the dianhydride and diamine are subjected to a condensation reaction in a polar solvent at low temperature to generate a solution of polyamic acid (PAA).
Step 2: After the PAA solution is cast or extruded into a film, it is then subjected to high-temperature imidization treatment to convert PAA into a polyimide film. The imidization process can be thermal imidization, which involves dehydrating and cyclizing PAA molecules through heating; It can also be chemical imidization, using dehydrating agents and catalysts to promote the imidization reaction of PAA.
Characteristics: The two-step method is beneficial for controlling the reaction process and can obtain polyimide films with high molecular weight and stable performance. The thin film produced by thermal imidization method has good performance, but it requires high equipment and consumes a lot of energy; The reaction conditions of chemical imidization method are relatively mild, but impurities may be introduced and require subsequent treatment.
3. Casting method
Process: The polyimide resin solution is uniformly cast onto a continuously running stainless steel strip or other smooth carrier. By controlling the casting speed, solution concentration, and drying conditions, the solvent evaporates to form a uniform film, which is then peeled off from the carrier and further cured and treated to obtain the polyimide film.
Features: It can prepare high-quality films with uniform thickness and smooth surface, suitable for producing various specifications of polyimide films, especially ultra-thin films. But the production efficiency is relatively low and the equipment investment is large.
4. Extrusion method
Process: After heating and melting the polyimide resin particles, they are extruded through the screw of an extruder to form a thin film. The film is then cooled and shaped on a cooling roller, and then subjected to processes such as traction and stretching to obtain a polyimide film.
Features: High production efficiency, suitable for large-scale production. It is possible to prepare films with certain tensile properties and orientation, and the thickness and properties of the films can be controlled by adjusting the extrusion process parameters. However, high requirements are placed on the fluidity and thermal stability of the resin, and the processing accuracy and process control of the equipment are difficult.
5. Blow molding method
Process: Heat the polyimide resin to a molten state, extrude it into a tube shape through an extruder, and then introduce compressed air into the tube to inflate the tubular film into a bubble shape. Under the action of a cooling air ring, it is cooled and shaped, and then the polyimide film is obtained through processes such as traction and winding.
Features: It can produce films with biaxial tensile properties, improving the mechanical and barrier properties of the films. The equipment is relatively simple and the investment cost is low. However, controlling the thickness uniformity of the film is difficult, and it is necessary to correctly control parameters such as inflation ratio and traction speed during the production process.
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