Surface Microstructuring For Structural Colors Effects On Synthetic Fiber By Hot-embossing

In the textile field, many of the advances of synthetic fiber technology are bases on modification or enlargement of the fiber surface as many properties of textiles are defined by the surface of the applied fibers. A method to produce fiber with accurate microstructures on the surface by roll embossing was developed by EMPA (Swiss Federal Laboratory for Material Research). One of the aims of the project which develops an approach of patterning textile fibers using thermoplastic molding to reach surface nanostructures by roll-hot embossing is to achieve optical effects by imprinting complex structures on fiber surface.The imprinting feasibilities and rotation imprinting were studied on crystalline monofilament fiber (PET, PP, PA 6, and PA 66), amorphous monofilament fiber (PMMA), bicomponent monofilament fiber (PET-PP), and multifilament (PA 66). It was indicated that all aforementioned synthetic fibers are feasible to be embossed with this prototype device within the feasible range of embossing parameter in this study.The relationship between the thermoplastic imprinting parameters (temperature, pressure, speed) and the performances of the structurally coloring fiber was investigated by the single factor experiments. It was observed that more uniform microstructure and stronger optical effects were obtained by imprinting with high temperature and high pressure which decreased the tensile of embossed fiber. The optical effect was reduced and the mechanical properties were increased with increasing embossing speed.The optimal combination of embossing parameters was proposed by making use of orthogonal experiments. For the width of the microstructure region on the embossed PMMA fiber, the most influential factor is the temperature; for the saturation, the most contributing factor is embossing pressure; for the mechanical properties, the most contributing factor is embossing speed. All-side evaluated, the optimal combination is considered as Temperature=100℃, Pressure=200mbar, Speed=3.4cm/s for the PMMA amorphous fiber.A plasma coating with silver was used to achieve reflective surfaces required for more obvious optical effects and the difference of the microstructure on fiber surface before and after coating was evaluated. The goniometric spectrum measurement was used to evaluate the structural colors and compare the structurally coloring fibers with the plasma-Ag-coated structurally coloring fibers. It was quantitatively proved that the microstructure on embossed fiber surface was changed by plasma coating. Different spectra giving rise to different color perception is a function of the rotation of detection angle. The optical effects were obtained through embossing the microstructures on fibers...