What is PI plastic?
Polyimide (PI for short) is one of the most heat-resistant and fire-resistant polymers currently available. Its low wear rate, ability to work without lubrication, and high pV rate make it an ideal material for high friction and wear applications, extending service life and reducing maintenance costs.
As a special engineering material, polyimide has been widely used in aviation, aerospace, microelectronics, nano, liquid crystal, separation membrane, laser and other fields. In the 1960s, countries were listing the research, development and utilization of polyimide as one of the most promising engineering plastics in the 21st century.
Key Features
High heat resistance
Excellent chemical resistance
High mechanical strength
Good dielectric properties
Applications
A. Film: One of the earliest products of polyimide, used for slot insulation of motors and cable wrapping materials. Transparent polyimide film can be used as a soft solar cell base plate.
B. Coating: Used as insulating paint for electromagnetic wires, or as high-temperature resistant coatings.
C. Advanced composite materials: Used in aerospace, aircraft and rocket components. It is one of the most high-temperature resistant structural materials. For example, the speed designed for the US supersonic passenger aircraft plan is 2.4M, the surface temperature during flight is 177℃, and the required service life is 60,000h. It is reported that 50% of the structural materials have been determined to be carbon fiber reinforced composite materials with thermoplastic polyimide as the matrix resin, and the amount used for each aircraft is about 30t.
D. Fiber: The elastic modulus is second only to carbon fiber, and it is used as a filter material for high-temperature media and radioactive substances, and bulletproof and fireproof fabrics.
E. Foam plastics: Used as high-temperature resistant insulation materials.
F. Engineering plastics: There are thermosetting and thermoplastic types. Thermoplastic types can be molded or injection molded or transfer molded. Mainly used for lubrication, sealing, insulation and structural materials. Guangcheng polyimide materials have begun to be used in mechanical parts such as compressor vanes, piston rings and special pump seals.
G. Adhesives: used as high-temperature structural adhesives. Guangcheng polyimide adhesives have been produced as high-insulation potting materials for electronic components.
H. Separation membranes: used for the separation of various gas pairs, such as hydrogen/nitrogen, nitrogen/oxygen, carbon dioxide/nitrogen or methane, and to remove moisture from hydrocarbon raw gas and alcohols in the air. It can also be used as a pervaporation membrane and ultrafiltration membrane. Due to the heat resistance and organic solvent resistance of polyimide, it is particularly important in the separation of organic gases and liquids.
M. Photoresist: There are negative and positive photoresists, and the resolution can reach submicron level. It can be used in combination with pigments or dyes for color filter films, which can greatly simplify the processing process.
I. Application in microelectronic devices: used as a dielectric layer for interlayer insulation, and as a buffer layer to reduce stress and improve the yield rate. As a protective layer, it can reduce the impact of the environment on the device, and can also shield the a-particles, reducing or eliminating the soft error of the device.
N. Orientation agent for liquid crystal display: Polyimide plays a very important role in the orientation agent materials of TN-LCD, STN-LCD, TFT-LCD and future ferroelectric liquid crystal displays.
K. Electro-optical materials: used as passive or active waveguide materials, optical switch materials, etc., fluorine-containing polyimide is transparent in the communication wavelength range, and polyimide as the matrix of the chromophore can improve the stability of the material.
J. Humidity-sensitive materials: It can be used to make humidity sensors based on the principle of its linear expansion due to moisture absorption.
Recycling of Polyimide
Physical recycling usually involves crushing and sorting the discarded polyetherimide to obtain recycled materials.
Chemical recycling is to decompose polyetherimide through chemical reactions to obtain raw materials or oligomers, and then polymerize them.
Challenges of recycling
Although the recycling of polyetherimide is of great significance, it still faces some challenges in actual operation. The chemical stability of polyetherimide is strong, so the decomposition and treatment technology in its recycling process needs to be further improved. The market acceptance and demand for recycled polyetherimide have not yet been fully formed, resulting in a low reuse rate after recycling. The lack of unified recycling standards and specifications also makes recycling work face certain difficulties.
