Methods for identifying various fibers
1. Visual inspection of hand feel
Fibers are identified based on their appearance, color, feel, stretch and other characteristics. It can be divided into Produce 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 artificially determined to a certain extent, it is difficult to distinguish them by visual inspection.
2. Combustion test method
The combustion method is a quick and easy 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, slowly approach the flame, and 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 fiber: 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 acetization, 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 is little flame and there is 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, Flame retardant or other finished fibers andTextiles, due to changes in combustion characteristics, are often difficult to identify by combustion.
3. Microscopic observation method
Microscopic observation method is to use 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 fiber cross-sections are mostly approximately circular. , must be verified using other methods.
Identification methods of several new textile fiber fabrics
At present, several new regenerated fibers developed and utilized in textile production are blended and interwoven with other kinds of textile fibers to produce For various new textile fabrics, to identify the components of these fabrics, we usually remove the warp and weft yarns of the fabric, and then untwist the yarns to remove the fibers. The identification analysis is as follows:
(1) First make a longitudinal film of the fiber. Observe the longitudinal shape of the fiber under a microscope. You can clearly distinguish whether it contains cotton or wool. The longitudinal shape of the soybean protein fiber has irregular grooves and island shapes. The uneven and uneven surface is different from the grooves on the longitudinal surface of Tencel fiber, Modal fiber, bamboo fiber and viscose-based chitin fiber, and can also be preliminarily 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.
The cross-sectional shape of vinylon fiber is a waist-round shape with a sheath and core layer, which 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 Triangles are similar to chemical fibers with a triangular cross-section; these can be distinguished by combustion and dissolution methods to determine whether cellulose fibers, plant protein fibers or chemical fibers are chemical fibers.
(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 In terms of tensile properties, the tensile breaking strength of bamboo fiber is higher than that of viscose fiber. The tensile elongation at break of viscose fiber is smaller than that of viscose fiber; although the cross-sectional shapes of viscose-based chitin fiber and viscose fiber are relatively similar, their edges are also zigzag-shaped, but the cross-sectional core of viscose-based chitin fiber There are obvious small gaps in the layers, while the cross-sectional shape of the viscose fiber is a zigzag shape with a sheath and core layer. reuse burningAccording to the method, the ash color is slightly different. The ash of bamboo fiber and viscose-based chitin fiber is gray-black, while the ash of viscose fiber is gray-white.
4. Solubility Experimental 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 are also exposed to some two- or three-component fiber blended products, which requires us to qualitatively identify the fibers first, pretreat the samples with appropriate methods, and then use appropriate The solvent dissolves one fiber of the blended variety, 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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