Polyimide (PI) is a polymer whose main chain contains acylimino groups (─C─N─C─), and there are two main categories:
Aliphatic (poor utility, non-commercial)
Aromatic (varieties obtained commercially)
Aromatic polyimides are divided into the following categories: homophenylene, mono ether, bis ether anhydride type, polyetherimide (PEI) , polybismaleimide, norbornene diacid-modified polyimide, polyamide imide (PAI). Pure PI is rarely used alone, the application of PI is mostly for its modified and composite varieties:
1, PI + long (carbon fiber, glass fiber, aramid fiber) fiber reinforced resin matrix composites;
2, PI + short cut (carbon fiber, glass fiber, aramid fiber) + (PTFE, graphite, molybdenum disulfide);
3, high temperature polyimide Adhesive;
4, High-temperature-resistant electronic packaging materials;
5, High-temperature-resistant coatings or films. (1) Flame retardant: PI is a self-flame retardant polymer and does not burn at high temperature.
(2) Mechanical properties (small sensitivity to temperature):
a, pure PI mechanical properties are not high, especially the impact strength is relatively low;
b, fiber reinforced will be greatly improved:
Impact strength: from 27J/m to 190J/m, an increase of more than 10 times;
Tensile strength: from 60Mpa to 1200Mpa. Tensile strength: from 60Mpa to 1200Mpa, more than 20 times;
Flexural modulus: from 3.8Gpa to 80Gpa, more than 20 times;
c, high creep resistance;
d, low coefficient of thermal expansion, high dimensional stability;
e, abrasion resistance (VS45# steel): only 0.04g of abrasion at 1000 rpm (can be filled with F4, disulfide composite). Can be filled with F4, molybdenum disulfide to further improve);
f , with self-wetting.
(3) excellent thermal properties:
a, high temperature resistance, low temperature resistance at the same time;
b, long-term use of the temperature: -200 ~ 300 ℃ (the first generation) ~ 371 ℃ (the second generation) ~ 426 ℃ (the third generation);
c, resistance to radiation
(4) outstanding electrical properties:
a, Dielectric constant: can be reduced to below 2.4 by design (ultra-low dielectric constant material with excellent comprehensive performance among super high temperature resistant plastics).
b, dielectric loss factor: 10 ~ 10;
c, arc resistance: 128s ~ 180s;
d, high electrical insulation;
(5) environmental performance (chemical resistance):
a, stable (resistance): acids, esters, ketones, aldehydes, phenols and aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons, etc.;
b, Unstable: chlorinated biphenyls, oxidizing acids, oxidizing agents, concentrated sulfuric acid, concentrated nitric acid, aqua regia, hydrogen peroxide, sodium hypochlorite; high-temperature polyimide super engineering plastics have many other engineering plastics do not have excellent performance: high temperature, low temperature, corrosion resistance, self-lubricating, low abrasion, excellent mechanical properties, good dimensional stability, small coefficient of thermal expansion, high insulation, low thermal conductivity, non-melt, no rust, and can be used to replace metals, ceramics and other materials in many cases. In many cases, it can replace metal, ceramics, PTFE and engineering plastics, etc. It is widely used in petrochemical industry, mining machinery, precision machinery, automotive industry, microelectronic equipment, medical devices and other fields, with a very good performance-price ratio. Widely used in aviation, aerospace, microelectronics, nano, liquid crystal, separation membrane, laser and other fields. Parts with low friction coefficient and wear resistance under high speed and high pressure Parts with excellent creep or plastic deformation resistance Parts with excellent self-lubrication or oil lubrication performance Liquid-sealed parts under high temperature and high pressure Parts with high resistance to bending, stretching and high impact resistance Parts with high resistance to corrosion, radiation, and rust Long-term use temperature exceeding more than 300 ℃, and short-term up to 400 ~ 450 ℃ parts
Typical applications include:
(1) parts with low friction coefficient and wear-resistant performance under high speed and high pressure;
(2) parts with excellent resistance to creep or plastic deformation;
(3) parts with excellent self-lubricating or oil lubrication performance;
(4) parts with liquid sealing under high temperature and high pressure;
(5) High bending, stretching and high impact resistance parts;
(6) corrosion-resistant, radiation-resistant, rust-resistant parts;
(7) long-term use of more than 300 ℃, short-term 400 ~ 450 ℃ parts;
(8) high-temperature (more than 260 ℃) structural adhesives (modified epoxy resin, modified phenolic resin, modified), and other temperature-resistant silicone adhesives. Organosilicon adhesives and other temperature resistance does not exceed 260 ℃ occasions);
(9) microelectronics encapsulation, stress buffer protective coating, multi-layer interconnection structure of the interlayer insulation, dielectric film, chip surface passivation.