In our previous studies, the polyamide materials, such as wool, silk, nylon 6, and tanned leather, were colored in a water solution containing reducing sugars, similar to the brownish coloration of various foods containing both protein and reducing sugars, and these coloration reactions are called Maillard reaction. Interestingly, the obtained color materials or their related materials give foods not only color but also distinctive flavor, anti-oxidative capacity, and anti-bacterial activity. In this paper, anti-bacterial properties of the polyamide fibers colored by the Maillard reaction were investigated using conventional methods of JIS L 1902. As a result, polyamide fibers reacted with xylose, one of reducing sugars, showed very strong anti-bacterial activity against both Gram-positive and Gram-negative bacteria, such as S. aureus, E. coli, and so on. However, a clear relationship between the color concentration of these fibers and their anti-bacterial properties was not observed.

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The cotton fibers, threads and fabrics which were repeatedly colored with clay minerals by the process of immersing, drying, and rinsing were observed with an optical microscope and a SEM. The particle size distribution of the clay suspension, absorption spectra of the filtration of the suspension and K/S values of the colored fabrics were measured by laser diffraction scattering method, uv-vis spectrophotometry and diffuse-reflectivity at 400 nm, respectively. As a result, it was revealed that the smaller the diameters of the clay particles were, and the more repeating the process of immersing, drying, and rinsing was, the more deeper coloration were obtained. The clay particles of 0.3～3μm were observed on fiber surface after coloring, though the average diameters of the clay used for coloration were approximately 10～14μm.

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As for measurement of the bending rigidity of thread, generally, the KES method has been used. A test sample based on the relation among the bending rigidity of a ring-formed beam, compression load and displacement is adopted. Results from the test samples are comparatively in agreement with those of KES method.

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