Polyimide: English name Polyimide (PI for short)
Polyimide as a special engineering materials, has been widely used in aviation, aerospace, microelectronics, nano, liquid crystal, separation membrane, laser and other fields. Recently, countries are researching, developing and utilizing polyimide as one of the promising engineering plastics in the 21st century. Polyimide, because of its outstanding features in performance and synthesis, whether as a structural material or as a functional material, its huge application prospects have been fully recognized, known as the “problem solver” (protion solver), and that “there is no polyimide will not have today's microelectronics technology.
Polyimide is a molecular structure containing imide-based chain links of aromatic heterocyclic polymer compounds, the English name Polyimide (referred to as PI), can be divided into benzene-type PI, soluble PI, polyamide-imide (PAI) and polyetherimide (PEI) four categories.
Polyimide PI is currently one of the best varieties of engineering plastics heat resistance, some varieties can withstand long-term high temperature of 290 ℃ for a short period of time to withstand a high temperature of 490 ℃, in addition to mechanical properties, fatigue resistance, flame retardant, dimensional stability, electrical properties are good, molding shrinkage is small, oil, general acid and organic solvents, do not resist alkali, has excellent friction, abrasion performance
Polyimide products Electronic and electrical applications, the electronics industry to do printed circuit boards, insulating materials, heat-resistant cables, terminals, sockets and other fields.
HONY Plastic specializes in the production and processing of polyimide rods, gaskets, and molded injection molding of various polyimide PI shaped products.
Performance of polyimide products
1, All aromatic polyimide according to thermogravimetric analysis, the beginning of decomposition temperature is generally around 500 ℃. Polyimide synthesized by biphenyltetracarboxylic acid dianhydride and p-phenylenediamine, the thermal decomposition temperature of 600 ℃, is so far one of the polymers in the thermal stability of the very high varieties.
2, Polyimide can withstand extremely low temperatures, such as -269 ℃ in the liquid helium will not be brittle.
3, Polyimide products have excellent mechanical properties, unfilled plastic tensile strength are more than 100Mpa, homobenzene-type polyimide film (Kapton) for more than 170Mpa, and biphenyl polyimide (Upilex S) to 400Mpa. as an engineering plastic, the amount of elastic film is usually 3-4Gpa, the fiber can be Reach 200Gpa, according to theoretical calculations, benzene tetracarboxylic acid dianhydride and p-phenylenediamine synthesized fibers up to 500Gpa, second only to carbon fiber.
4, Some varieties of polyimide insoluble in organic solvents, dilute acid stability, general varieties are not very resistant to hydrolysis, this seems to be a disadvantage of the performance of the polyimide is different from other high-performance polymers, a very big feature, that is, the use of alkaline hydrolysis recovery of raw materials, such as dianhydride and diamine, such as for the Kapton film, the recovery rate of up to 80% -90%. Change the structure can also get quite resistant to hydrolysis varieties, such as withstand 120 ℃, 500 hours of boiling.
5, The coefficient of thermal expansion of polyimide products in 2 × 10-5-3 × 10-5 ° C, wide into thermoplastic polyimide 3 × 10-5 ° C, biphenyl type up to 10-6 ° C, individual varieties of 10-7 ° C.
6, Polyimide has a high resistance to irradiation, its film in 5 × 109rad fast electron irradiation strength retention rate of 90%.
7, Polyimide products have good dielectric properties, dielectric constant of 3.4 or so, the introduction of fluorine, or air nanometer size dispersed in polyimide, the dielectric constant can be reduced to about 2.5. Dielectric loss of 10-3, dielectric strength of 100-300KV/mm, Guangcheng thermoplastic polyimide for 300KV/mm, volume resistance of 1017Ω/cm. these properties in a wide range of temperatures and frequency range can still be maintained at a high level.
8, Polyimide is a self-extinguishing polymer, low smoke rate.
9, Polyimide in a very high vacuum under very little outgassing.
10, Polyimide is non-toxic, can be used to manufacture tableware and * utensils, and withstand thousands of times. There are some polyimide also has a very good biocompatibility, for example, in the blood compatibility test for non-hemolytic, in vitro cytotoxicity test for non-toxic.
Application of polyimide products
As a result of the above polyimide in the performance and synthetic chemistry, in the many polymers, it is difficult to find such as polyimide has such a wide range of application aspects, and in each of these aspects have shown extremely outstanding performance.
1, Film: polyimide * one of the early commodities, used for motor slot insulation and cable winding materials. The main products are DuPont Kapton, UBE's Upilex series, and Jongbuchi Apical. transparent polyimide film can be used as a flexible solar cell backing plate.
2. Coatings: Used as insulating varnish for electromagnetic wires, or as high temperature resistant coatings.
3. Composites: Used in aerospace, aircraft and rocket components. It is one of the * high temperature resistant structural materials. For example, the United States of America's supersonic airliner program designed for the speed of 2.4M, the flight surface temperature of 177 ℃, the requirements of the service life of 60,000h, it is reported that has been determined that 50% of the structure of the material for the thermoplastic polyimide as a matrix resin carbon fiber reinforced composite materials, the amount of each aircraft is about 30t.
4. Fiber: modulus of elasticity second only to carbon fiber, as a high-temperature media and radioactive material filtering materials and bulletproof, fireproof fabrics.
6. Engineering plastics: thermosetting and thermoplastic, thermoplastic can be molded or injection molding or transfer molding. Mainly used for self-lubricating, sealing, insulation and structural materials. Guangcheng polyimide materials have begun to be used in compressor rotor blades, piston rings and special pump seals and other mechanical parts.
7. Adhesive: Used as high temperature structural adhesive. Guangcheng polyimide adhesive has been produced as high insulation potting material for electronic components.
8. Separation membrane: Used for the separation of various gas pairs, such as hydrogen/nitrogen, nitrogen/oxygen, carbon dioxide/nitrogen or methane, etc., and the removal of water from air hydrocarbon raw gas and alcohols. Also used as permeation evaporation membranes and ultrafiltration membranes. Due to polyimide heat and organic solvent resistance, in the separation of organic gases and liquids is of particular importance.
9. Photoresist: there are negative and positive adhesive, the resolution can reach submicron level. With pigments or dyes can be used for color filter film, can greatly simplify the processing procedures.
10. Application in microelectronic devices: used as a dielectric layer for interlayer insulation, as a buffer layer can reduce stress, improve yield. As a protective layer, it can reduce the impact of the environment on the device, and can also play a shielding role for a-particles, reducing or eliminating the soft error of the device.
11. Liquid crystal display with the orientation of the alignment agent: polyimide in the TN-LCD, SHN-LCD, TFT-CD and the future of the ferroelectric liquid crystal display of the orientation of the agent material are occupying a very important position.
12. Electricity - optical materials: used as passive or active waveguide materials optical switching materials, etc., fluorine-containing polyimide in the range of communication wavelengths for the transparent, polyimide as a chromophore matrix can improve the stability of the material.
In summary, it is not difficult to see the reason why polyimide can emerge from the 60s and 70s, many of the aromatic heterocyclic polymers stand out, * finally become an important class of polymer materials.
The role of polyimide gaskets in detail
Polyimide gasket is a high-performance plastic gasket made of polyimide material. This gasket plays an important role in industrial production, mainly reflected in the following aspects:
First, the role of sealing
Polyimide gaskets are often used as sealing materials because of their good elasticity and corrosion resistance. In the pipeline, valves, pumps and other equipment connections, the use of polyimide gaskets can effectively prevent gas or liquid leakage, to ensure the normal operation of the system.
Second, the role of insulation
Due to the excellent electrical insulation properties of polyimide materials, so polyimide gaskets are often used as insulating gaskets for electrical equipment. It can effectively isolate the circuit, prevent current leakage or short circuit, thus improving the safety and stability of electrical equipment.
Third, buffer effect
In mechanical equipment, many parts in operation will produce vibration and impact. Polyimide gasket because of its good elasticity and wear resistance, can play a buffer between these parts, reduce wear and noise, extend the service life of the equipment.
Fourth, chemical corrosion resistance
Polyimide materials have excellent chemical resistance, can resist a variety of acids, alkalis, organic solvents and other chemical substances. Therefore, in the chemical and pharmaceutical industries, polyimide gaskets are widely used in various pipelines, reactors and other equipment sealing and insulation.
In summary, polyimide gaskets play multiple key roles in industrial production. Its excellent high temperature resistance, corrosion resistance, wear resistance and good elasticity and electrical insulation properties, making it an indispensable part in a variety of machinery and equipment. Whether in the sealing, insulation, cushioning or chemical resistance, polyimide gaskets have shown excellent performance.
