Polyimide

1. Introduction to polyimide
Polyimide refers to a class of aromatic heterocyclic polymers containing imide groups in the backbone of macromolecules, abbreviated as PI in English.
There are many kinds of PI, and there are more than 20 kinds of industrial production, but there are mainly 4 commonly used: thermoplastic ether anhydride type and polyamide type PI, thermosetting homobenzene type and maleic anhydride type PI, among which thermoplastic ether anhydride type PI is the most commonly used, which can account for about 60~70% of the total amount.
The outstanding feature of PI is that it has good heat resistance, and the heat resistance temperature of thermosetting PI is as high as 360 °C, and the heat resistance temperature of thermoplastic PI can also reach more than 240 °C, which is a rare heat-resistant variety among plastics. In addition to this, the mechanical and electrical properties of PI are also very good.
2. Performance and processing applications
performance
(1) General performance PI is a flame-retardant variety, and the oxygen index can reach 36. PI has good gas barrier and low water absorption.
(2) Mechanical properties PI has good mechanical properties, especially excellent tensile strength, creep resistance, wear resistance and friction, and does not change much with temperature.
(3) Thermal performance PI has high heat resistance temperature, and the heat deflection temperature of benzene type PI is as high as 360 °C, and it can be used for a long time at 260 °C. Long-term use temperatures up to 300°C in the absence of oxygen. PI has a low coefficient of linear expansion.
(4) Electrical properties PI molecules contain polar groups, but due to the symmetry and rigidity of the structure, which affects the activities of the matrix groups, PI still has very good electrical properties. It has outstanding corona resistance and is one of the few corona resistant materials, with high dielectric strength and little influence of electrical properties by frequency.
(5) Environmental performance PI has excellent oil resistance and solvent resistance, but not alkali resistance, PI has good radiation resistance, and the strength decreases very little after being irradiated by 4.28×107GY cobalt 60 rays.
Processing method
Thermoplastic PI can be molded by injection molding and extrusion, while thermoset PI can be molded by molding, laminating, impregnation and casting.
Scope of application
(1) Electronic and electrical PI is especially suitable for the manufacture of high-temperature insulating materials, of which H and C grades are the mainstay, specifically: high-temperature sockets, printed circuit boards, computer hard disks, integrated circuit chip carriers and cables, etc.
(2) Auto parts are mainly used for pistons, speed control gears, propulsion rods and spring bases of automobiles.
(3) Mechanical parts such as bearings, bushings, piston rings, gears, cams, sealing materials, friction materials and guide wheels, etc.
(4) Aerospace engine tail nozzle and fish scales, spacecraft parts, etc.