Conductive Plastics

Conductive plastic is a kind of functional polymer material which is mixed with resin and conductive material and processed by plastic processing method. Mainly used in electronics, integrated circuit packaging, electromagnetic wave shielding and other fields. It is the most important category of conductive polymer materials. As the conventional application of plastics in the electrical field is as insulating materials, some people treat conductive plastics as special functional materials[ 1]

Conductive plastics raw materials, resins and conductive materials volume resistivity and surface resistivity are used to describe the properties of functional polymer materials such as electronics and integrated circuit packaging

catalogue

1 Introduction

2 source

3 Classification

▪   Structural conductive plastics

▪   Composite conductive plastics

4 purpose

5 new conductive plastics

Introduction editing voice

Most conductive plastics are made of insulating materials mixed with high concentration of filamentous carbon black and completely coking compounds. Both volume resistivity and surface resistivity are enough to describe their electrical properties. The electrical properties of the carbon fiber network structure depend on the method of preparing them, and also change with the change of mechanical bending and contact force[ 2]

Conductive plastics combine the conductivity of metal (that is, a certain voltage is applied at both ends of the material, and there is a current passing through the material) and various characteristics of plastics (that is, the material molecules are composed of many small, repeated structural units). In order to endow polymer with conductivity, it is necessary to introduce π - conjugated system into the main chain of polymer to form polymer with overlapping π - electron system. Moreover, the regular structure of polymer is also indispensable, and the dopant can win this task. Therefore, the first condition for the conductivity of plastic material is that it must have conjugated π - electron system, and the second condition is that it must be chemically or electrochemically doped, that is, the polymer chain gets or loses electrons through the redox process. Research progress shows that people can produce plastics with conductivity higher than copper, and plastics with conductivity higher than any other material at room temperature[ 3]

Source editor voice

We usually think that the conductivity of plastic is very poor, so it is used to make insulating jacket of wire. However, Australian researchers have found that when a thin metal film is covered on a plastic layer and mixed with the surface of polymer by ion beam, a low-cost, high strength, good toughness and conductive plastic film can be produced.

The team led by two experts from the University of Queensland, Australia, are Professor Paul Meredith and assistant professor Ben Powell, and an expert from the University of New South Wales, Professor Adam micolich. Their work has been published in ChemPhysChem. The study was based on an experiment conducted by Andrew Stephenson, a former doctoral student at the University of Queensland. Ion beam technology is widely used in the field of microelectronics industry to test the conductivity of semiconductors, such as silicon wafers. However, the attempt to apply this technology to plastic film materials started in the 1980s, and little progress has been made. Professor Meredith said: "the work of this group is simply to change the properties of plastic film materials with the help of ion beam technology, so that they have the function similar to metals, can conduct electricity as the guide wire itself, and can even become superconductors. When the temperature is down to a certain level, the resistance becomes zero."

In order to show the potential application value of this material, the group used this material to make resistance thermometer according to the industry standard. Compared with the same type of platinum resistance thermometer, the products made of new materials show similar or even better performance“ What's interesting about this material is that we retain almost all the advantages of polymers - mechanical flexibility, high strength, low cost, but at the same time it has good electrical conductivity, which is usually not what plastics should have Professor micawlin said“ 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 a very broad application prospect. "In fact, we can change the conductivity of this material by 10 orders of magnitude, which is like we have 10 billion choices when we make this material," he said. In theory, we can make plastics that are completely non-conductive, or plastics that are as conductive as metals, and all the possibilities in between

This new material can be easily manufactured by using the equipment commonly used in the microelectronic industry, and its antioxidant capacity to oxygen exposure is much higher than that of traditional polymer semiconductor materials. According to the researchers, the film material obtained by ion beam treatment of polymer will have broad application prospects, which is a combination of modern and future technologies.

Edit voice by category

Conductive plastics are usually divided into two categories.

Structural conductive plastics

It means that the plastic itself has "inherent" conductivity, and the polymer structure provides conductive carriers (electrons, ions or holes). After doping, the conductivity of these plastics can be greatly improved, and some of them can even reach the conductivity level of metals. There are two kinds of doping methods: chemical doping and physical doping. The dopants include electron acceptor, electron donor and electrochemical dopant. Doped polyacetylene is a typical example. The conductivity of doped polyacetylene can be increased to 104 Ω - 1 · cm-1 after adding electron acceptors such as iodine or arsenic pentafluoride.

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

Composite conductive plastics

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

Composite conductive plastics are easy to prepare and have strong practicability. They are often used in switches, pressure sensitive components, connectors, antistatic materials, electromagnetic shielding materials, resistors and solar cells[ 4]

Purpose edit voice

Conductive plastics are not only widely used in antistatic additives, computer anti electromagnetic screens and intelligent windows, but also widely used 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 promote the rapid development of molecular electronics. In the future, human beings can not only greatly improve the computing speed of the computer, but also reduce the size of the computer. As a result, some predict that laptops will fit into watches in the future.

With the rapid development of electronic and electrical appliances, integrated circuits and large-scale integrated circuits, including miniaturization and high-speed, the current used in them is mostly weak, which makes the power of control signal close to that of external invasion of electromagnetic wave noise. Therefore, it is easy to produce misoperation, image obstacles and sound obstacles, which hinder police communication, defense communication and aviation communication, It is necessary to adopt shielding measures for the obstacles of satellite assembly and commissioning. Conductive plastics are ideal shielding materials, which can be used as the shell of electronic devices to achieve shielding. Compared with the traditional conductive materials, it is lighter, easier to form and process, corrosion-resistant, easy to adjust resistance and lower total cost, so it needs to use conductive plastics to achieve shielding.

Many conductive materials or high conductive materials are used in many occasions, such as making electrodes, low temperature heaters, etc[ 1]

New conductive plastic editing voice

The South Korean Academy of science and technology recently polymerized polypyrrole to produce conductive plastics. This is a kind of energy storage body, which can be used in rechargeable polymer battery; It can also be used to make color change switch according to the redox effect produced repeatedly in the thin film state. It can also be coated on the surface of semiconductor electrode using solar cell to improve the performance. It can also be used in circuit design, or replace the existing battery and fax photos.