This paper describes the theoretical analysis on lock stitch seam structure, regarding a fabric as an elastic spring toward its thickness direction. The following equation has been derived on a curve of a sewing thread.
y=-P₀/F₀√F₀/Kcosh√K/F₀x/sinh√K/F₀a₀+h₀
where,
T₀: sewing thread tension at the end points of boundary sectional area of fabrics,
F₀: horizontal component of T₀,
P₀: vertical component of T₀,
h₀: thickness of fabric,
2a₀: length of stitch zone I,
K: elastic constant of fabric compression.
The validity of the equation was confirmed by showing the calculated results with following parameters sewing thread tension, elastic constant and fabric thickness.

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The changes of tensile strength of cotton, cuprammonium rayon, silk, wool and nylon 6 fibers exposed to nitrogen oxides (NO_x) and light under 3 different humidity conditions…dry, normal and wet conditions…were determined. Each kind of fibers exposed to the normal condition reduced its tensile strength most. By contrast, the exposure under the dry condition resulted in slight decrease in tensile strength. The decrease in tensile strength under the wet condition was intermediate between normal and dry conditions. The results suggest that the water content in fibers and atmospheric humidity seriously affect the reaction of NO_x and light with fibers. IR spectra of each fiber exposed to NO_x under the normal condition showed that silk and wool fibers underwent the nitration and nitric esterification, and cotton and cuprammonium rayon underwent oxidation. It was suggested that these fibers were damaged by nitric acid caused from the absorption of NO_x into the water in fibers.

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The effect of surfactants derived from amino acid on the detergency for carbon black soil, palmitic acid and mixed fatty acid as a model of oily soil from a cotton fabric were studied. In addition, the soiling of a polyester fabric by carbon black soil and emulsification of olive oil in N-acyle amino acid surfactant of aqueous solution were also estimated.
Since we have ascertained the excellent performance of N-acyle amino acid surfactant through an extensive investigation, we wish to report the results.
1) The detergency of carbon black component was effective for cotton fabric in the order of: soap>HS21 (N-acyle amino acid surfactant) >SDS at 20°C, 40°C and 60°C. The detergency of HS-21 was less decreased in the hard water than that of a soap, though the detergency of SDS increased with increa-sing water hardness.
2) The soiling of a polyester fabric by carbon black soil in HS-21 aqueous solution was very low, even if water hardness increased.
3) Since the emulsification with HS-21 was much superior to that of SDS, HS-21 were more effective in removal of palmitic acid and mixed fatty acid than SDS.
4) The fatty acid was removed from cotton fabrics in the order of C₈>C₁₀>C₁₂<C₁₈. A fatty acid of lower melting point except oleic acid was removed easier than those of higher melting point.
5) The removability of saturated and unsaturated fatty acid is dependent on the kind of fiber. Unsaturated fatty acid (oleic acid) was removed from a fabric in the order of: polyester>cotton. On the other hand the order of that of saturated fatty acid (palmitic acid) was cotton>polyester.

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