Conductive coatings are called special functional coatings and can be divided into structural conductive coatings (also known as non-additive conductive coatings) and blended conductive coatings. Structural conductive coatings are also called intrinsic conductive coatings, which use high molecular polymers with conductive properties as the main matrix resin in the preparation process of conductive coatings to finally realize the conductive performance of coatings. The polymer molecules that can be used as intrinsically conductive coatings contain long chains of conjugated bonds. With the increase of the electronic system, the electrons have stronger delocalization. When the conjugated structure in the molecular chain reaches a certain When the quantity is high, the polymer can provide electrons, and the generated electrons flow between the chain segments of the conjugated structure through carriers or transition between the chain segments to generate current, thereby realizing the conductive performance of the coating.
Blended conductive coatings are the most widely used conductive coatings at present. It achieves the electrical conductivity of the coating by mixing filler particles with excellent electrical conductivity into the film-forming resin itself which does not have electrical conductivity. Blended conductive fillers mainly include carbon-based and metal-based. Among them, carbon-based conductive coatings and metal-based conductive coatings are the focus of current research and development . Since the research and development of conductive coatings, carbon-based conductive coatings have been widely used in the field of antistatic due to their low price and good electrical conductivity. Application, metal-based conductive coatings developed later, mainly use conductive copper powder, nickel powder, silver powder, etc. as fillers for blended conductive coatings, which have more excellent conductive properties.
Carbon-Based Conductive Coatings
The conductive mechanism of carbon-based conductive coatings mainly has two points: one is that the added carbon-based particles contact each other to form a complex three-dimensional grid structure; the other is that the distance between filler particles is small enough to allow electrons Through the polymer thin layer under the action of thermal vibration . Graphite and carbon black are commonly used carbon-based conductive fillers. These two raw materials are relatively easy to obtain and low in price. They have received more attention in the research and development of low-end conductive coatings.
Metallic conductive paint
Metal-based conductive fillers mainly include silver powder, copper powder, nickel powder, etc. Due to its excellent conductivity, silver powder has become a metal-based conductive filler that was developed earlier, but the price of silver powder is relatively expensive, and it is prone to migration of silver ions, which affects the conductive stability of the coating. Silver-based conductive coatings are mainly used in fields .
As a filler for conductive coatings, copper powder needs to be surface treated, because copper powder is easy to oxidize and its oxides do not have conductivity. Usually, methods such as electroplating, phosphating treatment, reducing agent reduction and polymer dilution treatment are used to solve the problem of surface oxidation of copper powder. The commonly used surface treatment method is to plate silver on the surface of copper powder to obtain a composite coating with better electrical conductivity . This composite coating has excellent electrical conductivity, and its electromagnetic shielding effect can reach within a certain frequency band.
The overall performance of nickel-based conductive fillers is between the above two. There are experimental studies, using the method of chemical reduction to prepare ultra-fine nickel powder, and using fineness as the purpose of nickel powder mixed with it according to the ratio, the prepared nickel-based conductive coating has stable performance and excellent conductivity. The reason why this conductive coating has better conductivity is that the nickel powder with larger particle size can play a filling role, while the ultrafine nickel powder can contact each other to form a certain number of three-dimensional grid structures. Nickel powder can be used as conductive metal filler alone, and it can also be plated with silver on its surface to prepare alloy powder, which combines the advantages of silver powder and nickel powder
Metal oxide conductive paint
There are experimental studies that zinc oxide and aluminum oxide can be used to prepare aluminum-doped zinc oxide solid solution through replacement reaction. The conductive coating prepared by using this filler has strong chemical stability, strong anti-ultraviolet absorption ability, strong electrical conductivity and visible light transmission. Strong resistance and other characteristics, and the coating color is soft and bright. It has a wide range of applications , and has broad development prospects.
Composite Filler Conductive Coating
The application of composite conductive fillers can significantly reduce the production cost of conductive coatings. For example, silver powder can be coated on the surface of mica glass beads or metal powders which are not conductive and have low cost, thereby greatly reducing the preparation cost of conductive coatings and obtaining better conductive properties at the same time. The glass flake conductive coating prepared by the experiment has significantly shortened the drying and curing time of the paint film, significantly increased the thickness, and greatly improved the hardness and corrosion resistance.
The mixed use of fillers with different particle sizes in conductive coatings makes the gaps between larger filler particles filled by particles with smaller particle sizes, which increases the number of conductive filler particles in contact and forms more three-dimensional conductive network structures. At the same time, because the thickness of the insulating isolation layer between the particles is reduced, the resistance , and the conductivity of the coating is improved.
