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.Since plastic is usually used as insulating material in the electrical field, some people treat conductive plastics as special functional materials.[1]
The vast majority of conductive plastics are originally made of insulating materials mixed with high concentration of filamentous carbon black and fully coking compounds.useVolume resistivityandSurface resistivityIt is also sufficient to describe their electrical properties.The electrical properties of this carbon fiber network structure depend on the method of preparing them, and also change with the change of mechanical bending and contact pressure.[2]
Conductive plastic combines the conductivity of metal (that is, a certain voltage is applied at both ends of the material, and there is current in the material) and various characteristics of plastic (that is, the material molecule is composed of many small, recurring structural units).In order to endow polymers with conductivity, π conjugation system must be introduced into the main chain of polymers to form polymers with overlapping π electronic systems. Moreover, the regular structure of polymers is also indispensable, and dopants can overcome this task.Therefore, the first condition for a plastic material to have conductivity is that it must have a conjugated π electron system, and the second condition is that it must be chemically or electrochemically doped, that is, through the redox process to make the polymer chain gain or lose electrons.Research progress shows that people can produce plastics with conductivity more than copper, and plastics with conductivity more than any other materials at room temperature.[3]
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We usually think that the conductivity of plastic is very poor, so it is used to make the insulating jacket of wire.However, Australian researchers found that when an extremely thin metal film is covered with a plastic layer, and it is mixed with the surface of a polymer polymer by means of an ion beam, a plastic film with low price, high strength, good toughness and conductivity can be generated.
The team that achieved this result was composed of two people fromUniversity of Queensland The expert leaders of, respectively, Professor Paul Meredith and Assistant Professor Ben Powell, and one fromUniversity of New South WalesProfessor Adam Miccoli.Their achievement has been published in ChemPhysChem magazine.The research is based on the experiment ofUniversity of QueenslandDr. Andrew Stephenson.ion beamTechnology 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 has not made much progress.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 it has the function similar to metal, can conduct electricity as the guide wire itself, and can even becomeSuperconductorWhen the temperature is low to a certain extent, the resistance becomes zero. "
In order to show the potential application value of this material, the team used this material and madeResistance thermometer。In and of the same typePlatinum resistance thermometerDuring the comparative test, the products made of new materials show similar or even superior performance."The interesting thing about this material is that we almost keep itPolymerIt has all the advantages of mechanical flexibility, high strength and low cost, but at the same time it has goodConductivity, which is usually not a characteristic of plastics. "Professor Micolin said."This material has created a new world of plastic conductors."
Andrew Stephenson believes that the most exciting aspect of this technology is that the conductivity of this film can be precisely adjusted or set, which will have a very broad application prospect.He said, "In fact, we can change the conductivity of this material by 10Order of magnitudeIn a nutshell, it's like we have 10 billion choices when making this material.In theory, we can make completely non-conductive plastic, or plastic with conductivity as good as metal, and all the possibilities between the two. "
This new material can be easily manufactured by using the equipment commonly used in the microelectronics industry, and compared with the traditionalPolymer semiconductorThe antioxidant capacity of this new material to oxygen exposure is also much higher.The researchers said that combining these advantagesion beamProcessed from high polymerFilm materialIt will have broad application prospects. It is the integration of modern and future technologies.
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Conductive plastics are generally divided into two categories.
Structural conductive plastics
It means that the plastic itself has "inherent" conductivity, and the conductive carrier (electron, ion or hole) is provided by the polymer structure.After doping, the conductivity of such plastics can be greatly improved, some of which can even reach the conductive level of metals.Doping methods include chemical doping and physical doping. Dopants include electron acceptors, electron donors and electrochemical dopants.Doped polyacetylene is a typical example. After adding electronic receptors such as iodine or arsenic pentafluoride, the conductivity can increase to 10fourΩ-1·cm-1。
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 and only acts as an adhesive.Conductivity is obtained by mixing conductive materials such as carbon black, metal powder, etc.These conductive substances are called conductive fillers, and silver powder and carbon black are the most commonly used. They play a role in providing carriers in composite conductive plastics.
The composite conductive plastic is easy to prepare and has strong practicability. It is often used in switches, varistors, connectors, anti-static materials, electromagnetic shielding materials, resistors and solar cells.[4]
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Conductive plastics have not only developed rapidly in the application of antistatic additives, computer anti electromagnetic screens and smart windows, but alsolight-emitting diodeSolar cells, mobile phones, micro TV screens and even life science research also have broad application prospects.In addition, the combination of conductive plastics and nanotechnology will alsoMolecular electronicsThe rapid development of.In the future, human beings can not only greatly improve theOperation speedIt can also reduce the size of the computer.Therefore, some people predict that laptops in the future can be installed in watches.
With the development of electronic appliances, integrated circuits andlarge-scale integrated circuitThe rapid development of, including miniaturization and high-speed, its use of current is mostly weak current, resulting in the control signal power close to the power of external electromagnetic wave noise invasion, so it is prone to misoperation, image barriers and audio barriers, hinder police communications, defense communications and aviation communications, resulting in obstacles to satellite assembly and commissioning, and so on, which must be shielded.Conductive plastic is an ideal shielding material, which can be used as the shell of electronic devices to achieve shielding.Compared with traditional conductive materials, it is lighter, easy to form and process, corrosion resistant, easy to adjust resistance and low in total cost, so conductive plastics are needed to realize shielding.
In many occasions where conductive materials or high conductive materials are used, such as making electrodes, low-temperature heaters, etc., conductive plastics are the most suitable.[1]
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The South Korean Academy of Science and Technology recently obtained conductive plastics by chemical polymerization of polypyrrole.This is an energy storage body, which can be used for charging polymer batteries;It can also be used to manufacture a color change switch according to the redox effect repeatedly generated in the film state, and can also be coated on theSemiconductor electrodeThe surface is used to improve the performance, and can also be used for circuit design, or to replace the existing batteries and fax photos.[5]
