China has developed a new carbon fiber coloring technology for color carbon fiber fabrics.

Carbon fiber is widely used in aerospace, automotive, chemical, infrastructure, military, sports, energy, textile and other fields due to its unique physical and chemical properties. However, the graphite-like structure of carbon fiber makes its surface chemically inert, low in interface energy, poor in interface wetting property and high temperature oxidation resistance, and lacks chemical groups with high reactivity, which makes it impossible to form carbon fiber and other matrix materials. Effective interface coupling, interface strength decreases, which seriously affects its mechanical properties. In addition, the low chemical bond with the dye molecules makes it difficult to dye, resulting in a single color tone of the developed carbon fiber products, which is difficult to meet the fashion needs of consumers.

Existing methods for coloring carbon fiber fabrics include: weaving about 50% of dyeable yarns, such as glass fiber, polyester , copper, aramid, etc., but the mechanical properties of carbon fiber fabrics will also decrease accordingly; Apple announced One patent US7790637 B2 changes the appearance color of carbon fiber fabric by adding an additional "scrim". The University of Manchester recently developed a new electrochromic resin that can be used as a carbon fiber prepreg to produce a stable, reversible color change under the applied electric field.

Nevertheless, achieving direct coloration while maintaining the high mechanical properties of carbon fiber fabrics remains a challenge for scientists. Recently, Professor Wang Shimin of Hubei University and Professor Xu Weilin of Wuhan Textile University and other research teams have developed an effective and easy-to-operate carbon fiber fabric coloring method, which not only has adjustable color, but also has excellent washing resistance. This research has been published in the Facile and Effective Coloration of Dye-Inert Carbon Fiber Fabrics with Tunable Colors and Excellent Laundering Durability. According to the introduction, this research mainly uses the ALD (Atomic Layer Deposition) technology to construct amorphous TiO2 films with different scales on the carbon fiber/fabric surface to realize the coloration of carbon fiber and its fabric.

The structural color is a colorful biological color produced by a series of physical effects such as selective reflection, dispersion, scattering, interference, diffraction and transmission of visible light by a special optical scale microstructure. The color-developing mechanism of the structural color without pollution, high fading, high saturation brightness and no iridescent effect also makes it have the technical advantages and broad application prospects that other dyeing technologies cannot match. This provides a new way of thinking about the ecological coloration of carbon fiber.

Structural color in nature

Methods for constructing structural colors include sol-gel methods, self-assembly, holographic lithography, inkjet printing, anodization, electrophoretic deposition, electrospinning, and atomic layer deposition (ALD). ALD is a special chemical vapor deposition technology. Due to the self-limiting surface chemical reaction characteristics, atomic layer deposition technology has excellent shape retention, uniformity of large-area growth and precise controllable thickness of sub-monolayer film. Nano-scale controlled chemical bonding growth and excellent conformal properties make it both resistant to service, easy to operate, high in stability, independent of the size and shape of the substrate, and capable of controlling the composition of the film at the atomic level. Thickness, wide applicability, no pollution to the surrounding environment.

However, since the surface of the carbon fiber fabric is mainly a chemically inert sp2 bond, it is difficult to initiate the ALD reaction on the CFF. This study utilizes defects in the surface of carbon fibers and oxygen-containing functional groups (such as -OH and -COOH) to effectively initiate the growth characteristics of TiO2 films. First, TIP (titanium tetraisopropoxide) is introduced through the surface of carbon fibers -OH or - The self-limiting chemical reaction of the reactive groups of COOH forms -OCH(CH3)2 on the surface of the carbon fiber, and introduces H2O to react with -OCH(CH3)2 to form a single-layer TiO2 film and an exposed -OH, which is blown by nitrogen after each step. Except the remaining substances. By repeating the above number of ALD cycles, the desired TiO2 film thickness can be precisely adjusted.

TiO2 film wrapped around the outside of carbon fiber

By controlling the thickness of the amorphous TiO2 film, the study realized the successful preparation of the three primary colors red, yellow and blue, and can obtain various other colors by the combination of the three primary colors, that is, changing the thickness of the ALD TiO2 on the surface of the carbon fiber fabric. And the formed TiO2 film is excellent in washing resistance and can withstand 50 washings. This result points the way for the ecological coloration of carbon fiber and its fabrics.