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Views: 32 Author: Site Editor Publish Time: 2021-07-19 Origin: Site
In this paper, the main uses of PI materials are introduced:
(1) Film: one of the earliest products of polyimide, used for slot insulation of motor and cable wrapping material. The main products are Kapton of DuPont, upilex series produced by Yubu and apical of Zhong Yuan. Transparent polyimide film can be used as a soft solar cell substrate. A recent example is for this new type of LED lamp: innovative LED lamp
(2) Coating: used as insulating paint for electromagnetic wire, or as high temperature resistant coating.
(3) Advanced composite materials: used in aerospace, aircraft and rocket parts. It is one of the most heat-resistant structural materials. For example, the supersonic airliner program of the United States is designed with a speed of 2.4m, a surface temperature of 177 ℃ during flight, and a service life of 600000 h. It is reported that 50% of the structural materials are carbon fiber reinforced composites with thermoplastic polyimide as matrix resin, and the consumption of each aircraft is about 30t.
(4) Fiber: strength up to 5-6gpa, elastic modulus up to 250-300gpa, compared with T700 Carbon fiber, it can be used as reinforcing agent of advanced composite materials, high temperature medium, filter material of radioactive substances and bulletproof and fireproof fabric.
The properties of common fiber materials are as follows:
| Fibre | Density, g/cm | Modulus, MPa | Strength, MPa |
| Aramid-49 | 1.44 | 124 | 2.92 |
| PBT | 1.58 | 300 | 3.0 |
| PBO | 1.5 | 340 | 3.4 |
| Polyimide | 1.3-1.4 | 250－300 | 5.2 |
| Carbon Fibre | 1.77-1.96 | 822 | 5.3 |
Comparison of polyimide fiber and Kevlar fiber:
| Water absorptionperformance | PI fiber | Kevlar |
| modulus | 1400g/d | <1000g/d |
| Thermal oxidation stability | Keep the strength in air at 300 ℃ for 90% | Strength in air at 300 ℃ kept 60% |
| Water absorption | 0.65% | 4.56% |
| In water vapor at 200 ° C | Strength maintained 60% for 12 hours | 8 hours strength maintained 35% |
| Water resistance of 40% sulfuric acid at 85 ℃ | 250 hours strength maintained 93% | 40 hours strength maintained 60% |
| Water resistance in 10% NaOH at 85 ℃ | Strength drop 40% in 1 hour | 50 hour strength down 50% |
| Ultraviolet irradiation at 80-100 ℃ | 24 hours strength maintained 90% | 8 hours strength to keep 20% |
| Treatment of spinning liquid | The polymerization solution can be spun directly | After polymerization, it should be washed thoroughly before spinning solution is made |
(5) foam plastic: used as high temperature resistant thermal insulation material.
(6) Engineering Plastics: thermosetting and thermoplastic, can be molded, also can be injection molding or transfer molding. Mainly used for self lubrication, sealing, insulation and structural materials.
(7) Adhesive: used as high temperature structural adhesive.
(8) Separation membrane: used for the separation of various gas pairs, such as hydrogen / nitrogen, nitrogen / oxygen, carbon dioxide / nitrogen or methane, to remove water from air, hydrocarbon feed gas and alcohols. It can also be used as pervaporation membrane and ultrafiltration membrane. Polyimide is of great importance in the separation of organic liquids and gases due to its heat and solvent resistance.
(9) Photoresist: there are negative and positive photoresist, resolution up to submicron level. It can be used in color filter film with pigment or dye, which can greatly simplify the processing procedure.
(10) Application in microelectronic devices: as dielectric layer for interlayer insulation, as buffer layer can reduce stress and improve yield. As a protective layer, it can reduce the influence of environment on the device and shield a-particles to reduce or eliminate the soft error of the device.
(11) Polyimide as alignment agent for liquid crystal display plays an important role in TN-LCD, STN-LCD, TFT-LCD and future ferroelectric liquid crystal display.
(12) Electro optical materials: used as passive or active waveguide materials, optical switch materials, etc. the fluorinated polyimide is transparent in the communication wavelength range; The stability of the material can be improved by using polyimide as chromophore.
