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Recently, countries are listing the research, development and utilization of PI as one of the development priorities of
new chemical materials in the 21st century.
Polyimide, because of its outstanding characteristics in performance and synthesis, whether as a structural material or as a functional material, has great application prospects
.
Polyimide is known as the top material of the polymer material pyramid, also known as the "master of problem solving", and even some people in the industry believe that "without polyimide there would be no microelectronics technology
today.
"
Polymer material pyramid
.
Polyimide is versatile
with a wide range of applications and has shown outstanding performance in every application.
Below, Xiaobian will take you to understand the main uses
of various varieties of polyimide.
1.
Engineering plastics
, and have their own uses
in different fields.
PMMI heat distortion temperature of 360 °C under load of 1.
8MPa, excellent electrical properties, can be used for precision parts under special conditions, high temperature resistant self-lubricating bearings, sealing rings, blower impellers, etc.
, can also be used for valve parts in contact with liquid ammonia, jet engine fuel supply system parts
.
PEI has excellent mechanical properties, electrical insulation properties, radiation resistance, high temperature resistance and wear resistance, good melting fluidity, molding shrinkage of 0.
5% ~ 0.
7%, can be used injection and extrusion molding, post-treatment is easier, can also be combined with other materials by welding method, widely used
in electronic appliances, aviation, automobiles, medical equipment and other industries.
The strength of PAI is the highest among current non-reinforced plastics, with tensile strength of 190MPa, bending strength of 250MPa, and heat deflection temperature of up to 274°C
under 1.
8MPa load.
PAI has good ablation resistance and electromagnetic properties at high temperature and high frequency, and has good adhesion properties to metals and other materials, mainly used in gears, bearings and copiers separating claws, etc.
, and can also be used for ablative materials, permeable materials and structural materials
of aircraft.
2.
Polyimide fiber
organic synthetic fiber.
With the continuous development of high-tech fields, its requirements for the physical and chemical properties of PI products are getting higher and higher, traditional PI materials in mechanics, heat and optical, electrical, magnetic and other aspects of performance can not meet the special requirements of materials in the field of modern science and technology, PI high-performance fiber with its superior mechanical properties, thermal stability, radiation resistance and other characteristics will become a typical representative of
the next generation of high-performance fiber.
Polyimide fibers
3.
Photosensitive polyimide (PSPI)
with both imine rings and photosensitive genes on the polymer chain, integrating excellent thermal stability, good mechanical properties, chemical and photosensitive properties.
Photosensitive polyimide in the electronic field mainly has two major roles of photoresist and electronic packaging, in the photosensitive polyimide added sensitizer, stabilizer, etc.
can obtain "polyimide photoresist"
.
Compared with traditional photoresist, because polyimide itself has good dielectric properties, there is no need to apply a light blocker that acts as a working medium when using, which can greatly shorten the process and improve production efficiency
.
Limited by backward production technology, China's polyimide industry is still stable with low-end products such as films, photosensitive polyimide production is small, and market demand depends on imports
.
With the support of the "Made in China 2025" policy, China's industry, machinery, electronics and other fields have entered the stage of domestic substitution, and domestic enterprises have continued to deepen PSPI, and some enterprises have mastered production technology
.
Polyimide is used in photoresists
4.
Polyimide foam
。 Polyimide foam can be divided into three categories: (1) the same as general polyimide, using imide as the main chain foam material, the use temperature reaches 300 °C or more (PI foam) (2) the imide ring exists in the lateral group mode of foam material (PMI foam) (3) the thermal unstable fat chain segment is introduced into the polyimide and cracked at high temperature to obtain the nanofoam material
。 Polyimide foam materials are advanced functional materials, which have been increasingly used in key materials
such as heat insulation, vibration and noise reduction and insulation in high-tech fields such as aerospace, ocean transportation, national defense and microelectronics.
At present, the most important application of PI foam is the heat insulation and noise reduction materials for ships, and the Chinese navy is currently at the climax of the third ship building, PI foam as the preferred heat insulation and noise reduction material in new warships, the demand is rapidly increasing
.
Polymethacrylimide foam (PMI), which is a new type of polymer structure foam material with the best comprehensive performance, is a high-performance composite foam core material with high specific strength, high specific modulus, high closed cell rate and high heat resistance, which has the characteristics of
light weight, high strength, high / low temperature resistance.
In addition, PMI foam, as the most excellent structural foam core material, is widely used in wind turbine blades, helicopter blades, aerospace and other fields, and its replacement trend for PET foam is clear and the market space is broad
.
PI foam has strong heat resistance, good flame retardancy, no harmful gases, easy to install, and is a widely used heat insulation and noise reduction material
.
At present, the US Navy has used PI foam as a thermal and sound insulation material for all surface ships and submarines, and the SOLIMIDE foam produced by INSPEC has been developed by more than 15 countries for the insulation system of naval ships, in addition, PI foam is also widely used
in civilian ships such as luxury cruise ships, speedboats, and LNG ships.
Similar to PI foam, PMI foam is also widely
used.
Typical applications of PMI foam include: (1) structural foam core material: excellent high temperature compression resistance, making it widely used as a core material in wind turbine blades, aviation, aerospace, ships, transportation equipment, medical equipment and other fields; (2) Broadband transmission materials: low dielectric constant and loss make them widely used in radar, antennas and other fields; (3) Heat and sound insulation materials: high-speed locomotives, tires, audio, etc
.
5.
Polyimide coating
in coatings.
Enameled wire insulation coating mainly impregnates the outer layer of bare copper wire, alloy wire and glass wire clad wire of various types of wire diameters such as round wire and flat wire to improve and stabilize the outer layer
of enameled wire.
One of the important indicators of insulation coatings is the heat resistance grade, according to the ICE-85 thermal stability grading standard for motor and electrical insulation materials in use formulated by the International Electrotechnical Association in 1954, the insulation materials are divided into 7 heat resistance grades
.
The characteristics of the insulation material that meets the requirements of industrial technology development are that the insulation system should be able to work for a long time at 180-200 °C or even higher temperatures, but there is no significant weight loss and electrical strength reduction, and it maintains good elasticity, moisture resistance, ozone resistance, arc resistance and other properties
.
Polyimide materials can well meet this use requirement to prepare insulating coatings of F class and above heat resistance, polyimide can be used as insulating paint for electromagnetic wires, or as high temperature resistant
coatings.
6.
Polyimide adhesive
of low upper limit heat resistance temperature of other organic adhesives.
7.
Polyimide film
.
This time, Chang'e-4 successfully brought the national flag to the far side of the moon and marked the "China logo"
for space.
It is reported that the national flag of the probe is not made
of common chemical fiber fabrics, silk, cotton cloth and other textiles.
As we all know, the space environment is very special, there is no atmosphere on the surface of the moon, and when the vacuum receives sunlight, the maximum temperature on the lunar surface during the day can reach 123 °C
.
At night, outside the lunar module, the temperature on the moon plummets to minus 233 degrees Celsius
.
Such a temperature difference, ordinary materials are unbearable, and the ultraviolet rays produced by the sun are very strong, and there are also cosmic rays and high-energy particle radiation, which has a strong destructive effect
on materials.
The national flag material entrusted with the heavy responsibility is the polyimide organic polymer film, which is completely different from the common national flag on the ground, it can resist the harsh lunar surface environment, does not fade, does not deform.
In addition to being used as the "coat" of spacecraft and military applications, polyimide films can be seen in microelectronics, nano, liquid crystals, separation membranes, lasers, new energy fields and other fields
.
For example, transparent polyimide films can be used as flexible solar cell substrates; PI can be used as a next-generation separator material for lithium-ion batteries, etc
.
In recent years, with the development of the electronics industry, high-performance polyimide films have become the key materials for microelectronics manufacturing and packaging, which are widely used in the manufacture of VLSI circuits, automatic bonding carrier tapes, flexible packaging substrates, flexible connection strips and wires, etc
.
In addition, polyimide is an ideal material
for gas separation membranes with high temperature resistance due to its high heat resistance and good comprehensive properties.
At present, a very small number of polyimide varieties are used in high-temperature gas separation membrane materials, which are used for the separation of various gas pairs (such as hydrogen / nitrogen, nitrogen / oxygen, carbon dioxide / nitrogen, carbon dioxide / methane, etc.
), remove water from air, hydrocarbon raw gas and alcohols, and can also be used as pervaporation membranes and ultrafiltration membranes
.
However, conventional polyimide resins are difficult to dissolve and melt, thus limiting their wide industrial application possibilities
.
8.
Polyimide aerogel Polyimide aerogel (PIA) is an interlinked three-dimensional porous material composed of polymer molecular chains, combining the excellent properties of polyimide and aerogel, which not only has the excellent properties of polyimide, but also has the outstanding characteristics of aerogel, such as light ultra-low density, high specific surface area, low thermal conductivity, low acoustic impedance, environmental durability and low dielectric constant.
These special properties make polyimide aerogel materials have excellent application prospects
in thermal, electrical, mechanical, acoustic and other fields.
Polyimide aerogel
。 In addition to the aerospace field, polyimide aerogel materials have good application prospects
in electronic communications, thermal insulation and flame retardant materials, adsorption cleaning, sound insulation and sound absorption, catalytic carriers, wire/cable insulation layers and other fields.
9.
Polyimide matrix composites
used.
Polyimide resin matrix composites have the characteristics of high heat resistance, excellent mechanical properties, dielectric properties, solvent resistance, etc.
, and are currently the highest temperature resin matrix composites, which have been widely used
in aviation (especially aero-engines), aerospace and other fields.
After nearly 40 years of development, polyimide high-temperature resin matrix composites have developed four generations of composite materials, the use temperature has been continuously improved, and the most advanced fourth-generation polyimide resin matrix composites can be used
for a long time at 450°C.
At present, the application and research and development of polyimide composite materials in China are still catching up, and AVIC Composite Materials Company and other enterprises have been able to produce third-generation resin products
.
In addition, with the gradual maturity of the carbon fiber industry, the demand for carbon fiber reinforced composite materials has increased significantly, and the combination of polyimide + carbon fiber, as one of the most excellent composite material combinations, has obvious
advantages in seizing the high-end market.
epilogue
Polyimide includes almost all kinds of polymer materials, including high-performance films, engineering plastics, foams, chemical fibers, adhesives, resin matrix, insulating materials, functional materials, composite materials, etc.
The performance of polyimide is strongly dependent on its chemical structure, and polyimide with different structures can be selected or synthesized according to the use, and can also be modified by copolymerization, blending, filling, and enhancement
.
The development of new polyimide is inseparable from the development of new monomers, special structure of diamine and dianhydride monomer is the necessary guarantee for the development of new varieties of polyimide, reducing the cost of monomers is the key
to reducing polyimide.
Due to the irreplaceable role of polyimide-related materials in sensitive fields such as aerospace, military, and high-end electronics, most of the foreign polyimide raw materials, technologies and products are strictly blocked
in China.
Although domestic enterprises are already trying to catch up, there is still a big gap
between our domestic and mass-produced high-end products and foreign advanced levels.
Therefore, it is urgent to vigorously develop polyimide related products, and the task is arduous!
.
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.
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