Carbon Fiber Surface Treatment Technology is Worth Learning

 

 

Due to the inertness of the carbon fiber surface, the stress load between the carbon fiber and the matrix material in the composite material cannot be effectively transferred, which directly affects its performance and limits its large-scale application. Therefore, the carbon fiber needs to be surface treated. The surface activity of the carbon fiber is improved through surface modification technology, the interface performance between the carbon fiber and the matrix material is strengthened, and the bonding effect between the carbon fiber and the matrix is ​​improved, thereby increasing the value of the fiber material in industrial applications.

 

Coating Method

The coating method refers to coating a layer of polymer, metal particles or inorganic non-metal and their composites on the surface of the carbon fiber. The purpose is to change the surface wettability of the carbon fiber and increase the compatibility between the polymer matrix and the carbon fiber. Surface coating treatment not only participates in the formation of the interface phase between the fiber/matrix and reduces the thermal residual stress between the fiber/matrix during the manufacturing process of the composite material, but also reduces stress concentration and averages the surface performance of the fiber.

 

Plasma Treatment

The plasma spraying process is a high-speed collision deposition process in which a molten or semi-molten material is sprayed onto a pretreated matrix to form a coating. Plasma treatment has the advantages of simple operation, environmentally friendly process, and low destructiveness to the performance and mechanical strength of the original fiber. It has become a widely used research method.

 

Gas Phase Oxidation Method

The gas phase oxidation method is to use hot air, oxygen (O2), carbon dioxide (CO2), ozone (O3) and other gases as media to oxidize CF. After treatment, the specific surface area and surface roughness of CF increase, and the types and number of oxygen-containing functional groups on the surface also increase, thereby improving the comprehensive mechanical properties of CF reinforced composite materials.

 

Liquid Phase Oxidation Method

The liquid phase oxidation method is to use concentrated nitric acid, concentrated sulfuric acid, hydrogen peroxide and other oxidants to contact CF for a long time, forming carboxyl, hydroxyl and other groups on the fiber surface to enhance the bonding force with the resin.

 

Electrochemical Oxidation Method

Electrochemical oxidation is a method of surface treatment of CF using the conductive properties of CF, with CF as the anode, graphite, copper plate or nickel plate as the cathode, and different acid, alkali and salt solutions as the electrolyte under the action of a DC electric field. The effect of surface electrochemical oxidation treatment is a composite process of layer-by-layer oxidation etching and functional group changes.

 

Surface Grafting Method

The surface grafting method is to place carbon fiber in an active monomer atmosphere. Under the action of the initiator, the monomer reacts with the active group or edge carbon atom on the fiber.

 

Energy Beam Treatment Method

The surface performance is improved by using the changes in the material’s own organizational structure during the energy beam scanning process or by introducing other materials. The fiber will coarsen the surface under the irradiation of the energy beam and improve the adhesion with the matrix.

 

Rare Earth Treatment Method

Due to the chemical activity of rare earth elements and according to the chemical bond theory, rare earth elements can react with the C, O and N atoms on the surface of carbon fiber to form a coordination chemical reaction and chemical coordination bond. Rare earth elements have a large amount of charge. When surface treating carbon fiber, they can attract electrons in the carbon-carbon bond of carbon fiber, resulting in the electron element of the carbon-carbon bond shifting, making it easier to introduce functional groups into the surface of carbon fiber.

 

The key to carbon fiber modification technology is to improve the degree of bonding between carbon fiber and matrix and improve the performance of composite materials. With the increasing prominence of environmental problems, the low-cost, green and continuous production of carbon fiber surface treatment technology will be the key research direction in the future.