Abstract:

Objective Carbon fiber is widely used in aerospace, infrastructure, military equipment, sports and other fields due to its excellent physical and chemical properties. However, the color of carbon fiber is much too limited to meet the needs of various possible applications. At present, the colored carbon fiber is obtained by modifying its surface and then coloring it with chemical colorants. Although colored carbon fiber can be prepared by this method, the excellent properties of carbon fiber are negatively affected to a certain extent because of the surface modification before coloration. New technologies suitable for coloring carbon fiber are needed.
Method The coloring of carbon fiber was achieved through structural coloration. In this study, monodispersed poly(styrene-methacrylic acid) (P(St-MAA)) colloidal microspheres were prepared by soap-free emulsion polymerization, and were then used as building blocks to construct photonic crystal colored structures on carbon fiber/polyester blended yarns by a dip-coating method.
Results When the mass fraction of P(St-MAA) colloidal microspheres assembly solution was 70% and the self-assembly temperature was 40 ℃, brighter structural colors can be fabricated on the surface of carbon fiber(Fig. 3 and Fig. 6). It is seen that the process of self-assembly of P(St-MAA) colloidal microspheres on the yarn surface to form photonic crystals can be briefly categorized into preparatory stage, stacking aggregation stage and completion stage, and the corresponding structural color is formed with a series of color shifts(Fig.8-10). The colors presented by the yarn of the structural colored carbon fiber/polyester blended yarn varied with different observation angles, exhibiting a significant iridescent effect(Fig.11). The polydimethylsiloxane(PDMS)-encapsulated structural colored carbon fiber/polyester blended yarn can still maintain the original structural colors after washing and rubbing tests, indicating its outstanding color durability, as indicated in Fig.13-14.
Conclusion In this work, the photonic crystals composed of monodispersed P(St-MAA) colloidal microspheres were constructed via a dip-coating method to achieve structural coloration of carbon fiber. The mass fraction of P(St-MAA) colloidal microspheres solution-applied to fabricate photonic crystals on the carbon fiber was investigated and optimized at 70%. The effect of self-assembly temperature of carbon fiber on structural color effect was analyzed, and the research indicated that the self-assembly temperature had little effect on structural color. The process of self-assembly of P(St-MAA) colloidal microspheres on the yarn surface to form photonic crystals can be briefly categorized into preparatory stage, stacking and aggregation stage, and completion stage. Moreover, the structural colored carbon fiber/polyester blended yarn was encapsulated with PDMS to ensure the durability of structural colors. It was confirmed that the yarn color was still bright after multiple washing and rubbing tests, indicating the encapsulation of PDMS could effectively improve the stability of photonic crystals. The perfect combination of dip-coating method, carbon fiber and structural coloration is able to meet people's diversified demands for carbon fiber fashion and promote the industrial production of colorful carbon fiber materials.

Key words: carbon fiber, structural coloration, photonic crystal, poly(styrene-methacrylic acid), colloidal microsphere, self-assembly, polyester, blended yarn