Fiber and yarn identification

In practice, all chemical testing must be performed in accordance with specific standards, preferably internationally approved standards. Sometimes, the actual standard may be a mutually agreed and nationally accepted standard method of testing, or one that is based on the end-use of the product and other customer preferences. 

Cotton is the purest form of natural cellulose. Like all the vegetable tissues, it contains a small amount of mineral matter that is left as an ash after cotton is burned. The amount of ash is about 1-1.5%. The mineral matter in cotton consists of chlorides, carbonates and phosphates of potassium, calcium and magnesium. A large variation is observed in the amount of coloring matter found in cotton. The small amount of vegetable protein found in cotton is a little over 1 %. The impurity 

Raw cotton contains about 0.5% of a waxy substance which serves as a protective coating on the surface of the fiber. Cotton wax is insoluble in water and because of this, raw cotton is very hard to wet. It is well known that unbleached cotton will not soak up water as easily as bleached cotton. After cotton is purified, all of these impurities are reduced to a total of about %.  

There are several factors that influence the chemical analysis of raw cotton, but we can obtain a general idea from the following figures. If the impurities are calculated on an oven-dry basis, the percentage of fiber should be around 90%. It would be close to 99% after purification. Chemical analysis of the cotton fiber has shown the probable composition given in Table 1.1.  

The waxes are important in the spinning process but a hindrance to the dyeing operation. Owing to their water-repellent natuie, waxes prevent the proper absorption of the dyestuff. The natural color of cotton and the other impurities also interfere, but to a lesser degree, with the ordinary processes of dyeing, printing and finishing.  

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Near-infrared reflectance analysis is a useful technique for characterizing textile raw materials, fiber, yarns, and fabrics. It is a nondestructive quantitative analysis that is simple to use and allows rapid testing of the sample. Its ability to measure multiple components of the sample simultaneously and eliminate extensive sample preparation are major advantages of NIRA in the characterization of textile materials. Many innovative mathematical treatments, for example, discriminant analysis and spectral reconstruction, have been developed by instrument manufactures and software companies. These instruments not only aid in the quantitative analysis of the data but also allow morphological investigations of fibers and yarns and rapid, qualitative identification of specific sample sets. 

Research effort at Albany International Research Co. has developed unit processes necessary for pilot scale production of several species of reverse osmosis hollow fiber composite membranes. These processes include spin-dope preparation, a proprietary apparatus for dry-jet wet-spinning of microporous polysul-fone hollow fibers, coating of these fibers with a variety of permselective materials, bundle winding using multifilament yarns and module assembly. Modules of the membrane identified as Quantro II are in field trial against brackish and seawater feeds. Brackish water rejections of 94+% at a flux of 5-7 gfd at 400 psi have been measured. Seawater rejections of 99+% at 1-2 gfd at 1000 psi have been measured. Membrane use requires sealing of some portion of the fiber bundle for installation in a pressure shell. Much effort has been devoted to identification of potting materials which exhibit satisfactory adhesion to the fiber while... 

Microscopic examination All fibers have distinguishing features that allow either outright identification or classification into a narrower grouping for specialized analysis. Animal hair fibers, for example, have a characteristic scaled surface. In addition, many textile yarns are blends of two or more fiber types. A simple examination with a normal light microscope can establish this and allow the components of the yam to be separated for more detailed evaluation. The major identifying characteristics are ... 

Identification of different polymers, their properties, and their morphological differences normally requires extensive testing and complicated time-consuming analysis. Many statistical analysis methods have been combined with NIR to identify dissimilar textile products, including PCA, linear or multiple regression, PLS, derivative math, Mahalanobis distance (i.e.. Discriminate Analysis), nearest neighbors techniques, and neural networks. Most textile fibers, yarns, and fabrics have chemical sfrucfures fhaf yield complex NIR specfra, and as such these species normally require three or... 

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