In Japan, it is considered to be important to optimize the relation between “ structure of woven or knitted fabric “ and “ functional finish “ in order to gain effective functional finishes.

Even though the same chemicals for water-repellent and oil-repellent finishes are used, the effect given by these chemicals varies depending on the fabrics to be treated or on the finishing mills. Whether the suitable structure of fabrics is employed or not is especially important.

Recently, in the technical textile area, resin coatings are gradually changing from organic solvent types to aqueous types. With an advance in this change, the structure of fabrics to be coated and the selection of optimum coating machines are regarded as important. European literature said that fluorocarbon chemicals are effective for improving soil-repellency. In Japan, there are a few opinions that specialized silicones may be major in the future.

Dr. Wakida (emeritus professor of Kyoto Institute of Technology) et al presented new ideas of water repellency on the occasion of the annual meeting of The Society of Fiber Science and Technology in Gifu (Japan) on June 2005. The content of this discussion is the change of the fiber surface properties caused by washing and heat treatment of water-repellent woven fabrics. Silk palace and wool tropical were treated with zirconium based water-repellent finishes and silicone resins by the pad-dry-cure process. KES, shear and bending properties of these treated fabrics are measured. The water- repellency of these fabrics decreases with washing but recovers through heat treatment. Mechanical properties of zirconium-based water-repellent finishes were also explained in detail⁷⁾. Theoretical analysis on water-repellency will progress, and many technical experts expect Dr Wakida to continue his work.

Mr. K. Nishi (Meisei Chemical, Japan) et al also presented on the related subject “ Effect of washing and heat treatment on nylon 6 and triacetate fabrics treated with hydrocarbon water-repellent finish “.

On the other hand, the presentation of Mr. Y. Yanai (Shinshu Univ. )et al, which was the relation between liquid ammonia treatment conditions and the structure change of cotton, drew much attention⁸⁾. The summary of this presentation was that a change of processing speed on the bulk liquid ammonia treatment machine alters the degree of dryness and finally leads to changes in the structures of both crystalline and amorphous parts. With the advance of drying, the portion of type Ⅲ crystalline becomes higher. (Crystalline form of cotton changes from type Ⅰ to type Ⅱor type Ⅲ by chemical treatment.) And with an increase in the rate of drying, the portion of the amorphous part increases. The change of the amorphous part is very complex ; crease-resistant properties, tensile strength and flex rigidity increase, but pore volume and moisture retention decrease, with an increase the rate of drying. The moisture regain and tensile strength increase at the beginning of drying, but above a certain point they gradually decrease with the advance of drying. The exhaustion degree of the dye also slightly increases with liquid ammonia treatment, but its relation to the degree of drying is very complicated⁸⁾. This result is expected to be applied to bulk production.

Reference
7-8)From the annual meeting of The Society of Fiber Science and Technology, Japan 2005.