Identification methods of various fibers 1. Visual hand inspection method is to identify fibers based on their appearance, color, feel, stretch and other characteristics. It can distinguish natural fibers and chemical fibers. For example, natural fibers have poor length uniformity, while chemical fibers are generally more uniform in length. Among natural fibers, cotton fibers are short and thin, often accompanied by various impurities and defects. Hemp fiber feels rough and stiff. Wool fibers are curly and elastic. Silk is filament, long and slender, with a special luster. Among chemical fibers, viscose fiber has a large difference in dry and wet strength, while spandex has high elongation and high elasticity. Using these characteristics, they can be distinguished. Since the appearance characteristics of other chemical fibers are similar and can be determined by humans to a certain extent, it is difficult to distinguish them by visual inspection. 2. Combustion Experiment Method The combustion method is a quick and simple method to identify major categories of textile fibers. He roughly differentiates fibers based on their different burning characteristics. The method of identification is to take a small bundle of unknown fibers, hold it with tweezers, and slowly approach the flame. Observe the burning state of the fiber when it is close to the flame, in contact with the flame, and when it leaves the flame, as well as the smell emitted during burning and the characteristics of the residue after burning. , to roughly identify fibers. Acetate: melts and shrinks when exposed to fire. It burns immediately when exposed to fire and burns slowly. Although acetate fiber is also a regenerated cellulose fiber, it has become a semi-synthetic fiber after acetic esterification, so it has a pungent acetic acid smell when burned. The ash is black and not only loose but brittle. The unburned parts turn into hard pieces. Polyester: It curls, melts and burns with smoke when burning, and the flame is yellow. It emits an aromatic smell when burned, and the ashes are in the shape of dark brown glass balls that can be crushed by hand. Nylon (nylon): One side melts when exposed to fire, and the other side burns slowly. There is no smoke or slight white smoke when burning, and the flame is small and blue. It smells like celery when burning. The ashes are in the shape of light brown glass spheres and are not easily broken. Chlorine: It shrinks quickly when it is close to the flame and extinguishes when it is away from the fire. There is a pungent chlorine smell when burning. Ashes are amorphous black lumps. Vinylon: shrinks quickly when burned, but burns slowly. There was little flame and black smoke. There is an aldehyde smell when burning. Ashes are brown amorphous hard lumps that can be crushed. Acrylic fiber: melts and burns when exposed to fire, and the burning speed is very slow. The flame is white and very bright. Sometimes there is a little black smoke and a fishy smell. Ashes are small hard black balls that are brittle and brittle. It is simple and easy to identify fibers by combustion method, but it is difficult to judge blended products. For interwoven fabrics, one yarn is extracted from the warp and weft directions (that is, the straight and transverse directions) and burned separately. The burning method is only applicable to single-component fibers, yarns and fabrics, while for mixed-component fibers, yarns and fabrics, Fibers and textiles that have been flame retardant or otherwise treated are often difficult to identify by burning due to changes in combustion characteristics. 3. Microscopic observation method Microscopic observation method uses ordinary biological microscopes to observe the transverse and longitudinal morphology of unknown fibers to identify fibers. It is a method often used in fiber identification. The morphological characteristics of natural fibers are relatively unique. For example, wool has scales on its surface, cotton fibers have natural twists, hemp fibers have horizontal and vertical lines, silk cross-sections are triangular, and chemical fibers mostly have approximately circular cross-sections, which must be verified by other methods. . Methods for identifying several new textile fiber fabrics. At present, several new regenerated fibers developed and utilized in textile production are blended and interwoven with various other textile fibers to produce various new textile fabrics. To identify the components of these fabrics, we Usually, the warp and weft yarns of the fabric are removed, and then the yarns are untwisted to remove the fibers. The identification analysis is as follows: (1) First, make a longitudinal film of the fiber, and observe the longitudinal shape of the fiber under a microscope. You can clearly distinguish whether it contains The longitudinal morphology of cotton, wool, and soybean protein fibers has irregular grooves and island-like concave and convex surfaces, and the surface is not smooth, which is different from the longitudinal morphological grooves on the surface of Tencel fiber, Modal fiber, bamboo fiber and viscose-based chitin fiber. They are different and can be initially distinguished. (2) Use a slicer to slice the yarn, and observe the cross section of the yarn under a microscope. It is easy to determine whether it contains cotton fiber, silk, Tencel fiber, Modal fiber, and soy protein fiber. _(3) The cross-sectional shape of Modal fiber is similar to a waist-round shape and is relatively smooth with a sheath and core layer. It is obviously different from the cross-section shape of cotton fiber, which is a waist-round shape with a middle cavity. The waist round shape of the skin and core layer is also obviously different and can be distinguished. (4) The cross-sectional shape of Tencel fiber is round, similar to polyester and acrylic; the cross-sectional shape of soybean protein fiber is flat, dumbbell-shaped and waist-round, similar to vinylon; the cross-sectional shape of silk is triangular, which is similar to the triangular cross-section of soybean protein fiber. Chemical fibers are similar; these can be distinguished by combustion and dissolution methods to determine whether cellulose fiber, plant protein fiber or chemical fiber. (5) Although the cross-sectional shapes of bamboo fiber and viscose fiber are relatively similar, they are both zigzag-shaped and difficult to distinguish. Therefore, they can be distinguished by coloring and burning methods, or by comparing their tensile properties. Bamboo fiber The tensile breaking strength of plain fiber is higher than that of viscose fiber, and the tensile elongation at break is smaller than that of viscose fiber; although the cross-sectional shapes of viscose-based chitin fiber and viscose fiber are relatively similar, their edgesThe edges are also zigzag-shaped, but the cross-section core layer of viscose-based chitin fiber has obvious small gaps, while the cross-section shape of viscose fiber is zigzag shape with a skin-core layer. The combustion method was used to verify that the ash color was slightly different. The ash of bamboo fiber and viscose-based chitin fiber was gray-black, while the ash of viscose fiber was gray-white. 4. Solubility Experiment Method The dissolution method uses the principle of different dissolution characteristics of fibers in different chemical reagents to identify fibers. It is suitable for various fibers and their products and has a wide range of applications. In addition to qualitative analysis of fiber varieties, it can also conduct quantitative analysis of various blended yarns, fabrics and bicomponent fibers. This method is more accurate and reliable. After preliminary identification is made by other methods, it is confirmed by the dissolution method. However, in the experiment, the concentration of chemical reagents, treatment temperature and time must be strictly controlled to obtain more accurate experimental results. Based on the above situation, the fiber identification procedure is to sort out the unknown fibers a little first, and then use the combustion method to initially divide the fibers into three categories: cellulose fibers, protein fibers and synthetic fibers. Cellulose fibers and protein fibers have different morphological characteristics and can be identified using microscopy. Synthetic fibers are generally identified using the dissolution method. We also come into contact with some two- or three-component fiber blended products, which requires us to qualitatively identify the fiber first, pretreat the sample with appropriate methods, and then use an appropriate solvent to dissolve one component of the blended variety. The fibers are grown, and the remaining fibers are washed, dried, weighed and calculated. For example: a polyester-cotton cloth weighs 1.0 grams. Use 75% sulfuric acid to dissolve the cotton. The insoluble part is polyester and weighs 0.6 grams. Then the cloth contains 40% cotton and 60% polyester.
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