Conductive plastics are functional polymer materials that are processed by mixing resin and conductive materials in the same way as plastics. They are mainly used in the fields of electronics, integrated circuit packaging, electromagnetic wave shielding, etc.

Introduction

Most conductive plastics are made by adding high concentrations of filamentary carbon black and completely coked compounds to insulating materials. Volume resistivity and surface resistivity are also sufficient to describe their electrical properties. This electrical property, which relies on the carbon filament network structure, depends on the method of preparing them and also changes with changes in mechanical bending and contact force.

Conductive plastics combine the conductivity of metals (i.e., a certain voltage is applied to both ends of the material, and current flows through the material) and various properties of plastics (i.e., the material molecules are composed of many small, recurring structural units). In order to give polymers conductivity, a ¦Ð conjugated system must be introduced into the polymer main chain to form a polymer with overlapping ¦Ð electron systems. In addition, the regular structure of the polymer is also indispensable, and dopants can do the job. Therefore, the first condition for a plastic material to be conductive is that it must have a conjugated ¦Ð electron system, and the second condition is that it must be chemically or electrochemically doped, that is, the polymer chain gains or loses electrons through a redox process. Research progress shows that people can produce plastics that are more conductive than copper, and plastics that are more conductive than any other material at room temperature.

Source

We usually think that plastics are very poor conductors of electricity, so they are used to make insulating jackets for wires. But Australian researchers have found that when a very thin metal film is coated on a plastic layer and mixed into the surface of a polymer with the help of an ion beam, a low-cost, high-strength, tough and conductive plastic film can be generated.

The team that achieved this result was led by two experts from the University of Queensland, Australia, Professor Paul Meredith and Assistant Professor Ben Powell, and an expert from the University of New South Wales, Professor Adam Micolich. Their results have been published in the journal ChemPhysChem. The research was based on experiments conducted by Andrew Stephenson, a former PhD student at the University of Queensland. Ion beam technology is widely used in the microelectronics industry to test the electrical conductivity of semiconductors such as silicon wafers. However, attempts to apply this technology to plastic film materials only started in the 1980s and have made little progress. Professor Meridis said: "In simple terms, the work done by this team is to use ion beam technology to change the properties of plastic film materials so that they have metal-like functions, can conduct electricity like the wire itself, and can even become a superconductor, with zero resistance when the temperature drops to a certain level." To demonstrate the potential application value of this material, the team used this material to make resistance thermometers based on industrial standards. When compared with the same type of platinum resistance thermometer, the products made of the new material showed similar or even superior performance. "The interesting thing about this material is that we have retained almost all the advantages of polymers - mechanical flexibility, high strength, low cost, but at the same time it has good conductivity, which is not usually a property of plastics," said Professor Micolyn. "This material opens up a new world for plastic conductors." Andrew Stephenson believes that the most exciting thing about this technology is that the conductivity of this film can be precisely adjusted or set, which will have very broad application prospects. He said: "In fact, we can change the conductivity of this material by 10 orders of magnitude. Simply put, it's like we have 10 billion options in our hands when making this material. In theory, we can make plastics that are completely non-conductive, or plastics that are as conductive as metals, and all the possibilities between the two." This new material can be easily manufactured using equipment commonly used in the microelectronics industry, and compared with traditional polymer semiconductor materials, this new material has much higher antioxidant capacity when exposed to oxygen. Researchers said that with the above advantages, this thin film material obtained by ion beam treatment of polymers will have broad application prospects. It is a fusion of modern and future technologies. Classification Conductive plastics are generally divided into two categories.

Structural conductive plastics

refers to plastics that have "inherent" conductivity, and the polymer structure provides conductive carriers (electrons, ions or holes). After doping, the conductivity of this type of plastic can be greatly improved, and some of them can even reach the conductivity level of metals. There are two major methods of doping: chemical doping and physical doping. Dopants include electron acceptors, electron donors and electrochemical dopants. Doped polyacetylene is a typical example. After adding electron acceptors such as iodine or arsenic pentafluoride, the conductivity can be increased to 10¦¸¡¤cm.

Structural conductive plastics can be used to make high-power plastic batteries, high-energy density capacitors, microwave absorbing materials, etc.

Composite conductive plastics

In composite conductive plastics, the plastic itself does not have conductivity and only acts as a binder. The conductivity is obtained by mixing conductive substances such as carbon black and metal powder in it. These conductive substances are called conductive fillers, with silver powder and carbon black being the most used. They play the role of providing carriers in composite conductive plastics.

Composite conductive plastics are easy to prepare and have strong practicality. They are often used in switches, varistor components, connectors, antistatic materials, electromagnetic shielding materials, resistors and solar cells.

Applications

Conductive plastics have not only been rapidly developed in antistatic additives, computer anti-electromagnetic screens and smart windows, but also have broad application prospects in light-emitting diodes, solar cells, mobile phones, miniature 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 improve the computing speed of computers, but also reduce the size of computers. Therefore, some people predict that future laptops can be installed in watches.

With the rapid development of electronic appliances, integrated circuits and large-scale integrated circuits, including miniaturization and high speed, the currents used are mostly weak currents, which makes the control signal power close to the power of external intrusive electromagnetic wave noise, so it is easy to cause malfunctions, image barriers and sound barriers, hinder police communications, defense communications and aviation communications, and cause obstacles to satellite assembly and debugging, etc. Shielding measures must be adopted for this. Conductive plastic is an ideal shielding material and can be used as the shell of electronic devices to achieve shielding. Compared with traditional conductive materials, it is lighter, easier to shape and process, more corrosion-resistant, easier to adjust resistance and has a lower total cost, so conductive plastic is needed to achieve shielding.

Many occasions where conductive materials or high-conductivity materials are used, such as making electrodes, low-temperature heating elements, etc., are most suitable for using conductive plastics.

New Model

The South Korean Academy of Science and Technology recently obtained conductive plastics by chemically polymerizing polypyrrole. This is an energy storage body that can be used in rechargeable polymer batteries; it can also be used to make color-changing switches based on its repeated redox reactions in a thin film state. It can also be coated on the surface of semiconductor electrodes used in solar cells to improve performance. It can also be used in circuit design, or to replace existing batteries and to fax photos.

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