Conductive plastics are functional polymer materials that are mixed with resins and conductive materials and processed with plastic processing methods. Mainly used in electronics, integrated circuit packaging, electromagnetic shielding and other fields.
Conductive plastics have not only been used in antistatic additives, computer anti-electromagnetic screens and smart windows, but also have a wide range of applications in light emitting diodes, solar cells, mobile phones, micro-TV screens and even life science research. In addition, the combination of conductive plastics and nanotechnology will also promote the rapid development of molecular electronics. In the future, humans can not only greatly increase the computing speed of computers, but also reduce the size of computers. Therefore, it was predicted that future laptops could be loaded into watches.
First, the main use of conductive plastics (1) in the field of electronics, electrical appliances, integrated circuits, wafers, sensor jackets and other precision electronic components used in the production process of anti-static turnover box, IC and LCD trays, IC packaging, wafer carrier, Film bags and so on.
(2) Shells and structural parts of explosion-proof products, such as shells and structural parts of electrical products used in coal mines, oil tankers, oil fields, dusts, and combustible gases.
(3) Semi-conductive shielding materials used in medium and high voltage cables.
(4) EMI shielding enclosures for electrical products in fields such as telecommunications, computers, automation systems, industrial electronic products, consumer electronics, and automotive electronics.
Second, the state of development of conductive plastics at home and abroad 1, antistatic agent Filled antistatic agent Filled product has the advantage of product coloring is not limited, which low molecular antistatic agent has little effect on product performance, the surface resistivity 1010-1013Ω. However, the electrical properties of low molecular antistatic agent filled products will gradually lose over time.
The current development trend in foreign countries is the development and production of polymer antistatic agents. Polymeric antistatic agents can also be called permanent antistatic agents. They will not be washed after long-term use as low molecular antistatic agents do. Loss of its conductivity. The main varieties of polymer antistatic agents are: polyether type, quaternary ammonium salt type, sulfonic acid type, acid graft copolymer, ion type. The main manufacturers are Japan's Sanyo Chemicals, Sumitomo Precision, Sumitomo Science and Industry, Daiichi Pharmaceutical, Ciba Seiki in Switzerland, Clariant, Weike in the United States, and Great Lakes. The amount of the polymeric antistatic agent is 5-15 times that of the low molecular antistatic agent, and the compatibility with the resin must be considered in order to select the suitable compatibilizer, and the application is subject to cost constraints. Certain restrictions. At present, there are mainly low-molecular-weight antistatic agents in China. Representative manufacturers include Hangzhou Plastics Research Institute and Beijing Chemical Industry Research Institute.
2. Carbon-based filling This series of fillers are mainly conductive carbon black, graphite and carbon fiber. The volume resistivity of the finished product is 102-109 Ω·cm. Carbon black is the mainstream, and carbon black-filled conductive polymers are widely used because of the low price of conductive carbon blacks. The second reason is that carbon blacks have a great deal of choice according to different conductivity requirements. The resistance value of its finished products can be varied within a wide range between 102-109Ω. The third is the long-lasting and stable conductivity; therefore, it is an ideal antistatic material. However, its finished products are limited to black color and have a great influence on the properties of materials, and need to be matched with modification techniques.
In foreign countries, carbon-filled conductive plastics have formed a very mature market. The larger manufacturers include Cabot Corporation of America, former Union Carbon Corporation, GE Corporation, 3M Corporation, etc., Japan’s Toshiba Chemicals and Sumitomo phenolics. Plastics are the main manufacturers, including Toray, Toyo Ink Manufacturing, Tokyo Ink, Japan Synthetic Rubber, Kobe Steel, etc., PREMIX in Finland, and LG in Korea.
3, metal-filled type This type of conductive plastic is mainly used for electromagnetic shielding applications. In recent years, due to the development of integrated circuits and large-scale integrated circuit technologies, digital electronic machines have been developed from industrial to residential products. In order to increase the processing capacity, the electronic circuits and components used are increasingly integrated into miniaturization and high speed, and their signal levels are reduced, which makes electromagnetic waves invaded from the outside close to the control signals. In addition, the electronic device also emits electromagnetic waves to the outside, so that it is easy to cause malfunctions of electronic devices, and disturbances of images and sounds. In the 80's, most of the casings of electronic machines used plastic materials instead of metals. This is due to the fact that plastic as a housing has the advantages of light weight and high strength, corrosion resistance, easy processing, high production efficiency, and low overall cost. However, plastic is an insulator and is completely transparent to electromagnetic waves. Therefore, the ability to provide electromagnetic shielding of plastic enclosures has become a very urgent issue to be studied.
In recent years, the conductive plastic method has aroused people's interest, and there are many research reports in this area. This is because the conductive plastic method has three significant advantages: 1 It does not require secondary processing; 2 The shielding and molded products are completed once ); 3 in the long-term use of the process (such as vibration, hot and humid environment factors) safe and reliable, as the surface method does not produce peeling and shedding phenomenon.
Third, the development prospects Polymer materials instead of metal materials in the future development of materials disciplines. As a result, the market demand for conductive polymers has been increasing, and their application fields have been gradually expanded, which inevitably imposes higher requirements on conductive polymers. For the structural conductive polymer, in order to further practical use, it is necessary to solve the following main problems that currently exist:
(1) Lack of stability The oxygen atom in the conductive polymer is extremely unstable to water, which is the biggest problem that hinders its practical use.
(2) Doping agents are mostly toxic, such as AsF5, I2, Br2, etc.
(3) Molding difficulties The conjugated structure in the main chain of the conductive polymer makes the molecular chain rigid, insoluble, and infusible, thus making it difficult to form and process freely.
(4) Poor economic efficiency The price is higher than that of metals and ordinary plastics, and it is difficult to put them into practical use.