1.Sensory identification
(1) Main methods
Eye observation: use the visual effect of the eyes to observe the luster, dyeing, roughness of the surface, and the appearance characteristics of the organization, grain and fiber.
Hand touch: use the tactile effect of the hand to feel the hardness, smoothness, roughness, fineness, elasticity, warmth, etc. of the fabric. The strength and elasticity of fibers and yarns in the fabric can also be detected by hand.
Hearing and smelling: hearing and smelling are helpful to judge the raw materials of some fabrics. For example, silk has a unique silk sound; The tearing sound of different fiber fabrics is different; The smell of acrylic and wool fabrics is different.
(2) Four Steps
The first step is to preliminarily distinguish the major categories of fibers or fabrics.
The second step is to further judge the types of raw materials according to the sensory characteristics of fibers in the fabric.
The third step is to make a final judgment according to the sensory characteristics of the fabric.
The fourth step is to verify the judgment results. If the judgment is uncertain, other methods can be used for verification. If the judgment is wrong, the sensory identification can be conducted again or combined with other methods.
2. Combustion identification method
Combustion characteristics of common textile fibers
① Cotton fiber, burning in case of fire, burning fast, producing yellow flame and smell; There is a little grey white smoke, which can continue to burn after leaving the fire. After blowing out the flame, there are still sparks burning, but the duration is not long; After burning, it can keep the shape of velvet, and easily break into loose ash when touched by hand. The ash is gray and soft powder, and the charred part of the fiber is black.
② Hemp fiber, burning fast, softens, does not melt, does not shrink, produces yellow or blue flame, and has the smell of burning grass; Leave the flame and continue to burn rapidly; There are few ashes, in the form of light gray or white straw ash.
③ Wool does not burn immediately when it contacts the flame. It first shrinks, then smokes, and then the fiber starts to burn; The flame is orange yellow, and the burning speed is slower than that of cotton fiber. When leaving the flame, the flame will stop burning immediately. It is not easy to continue burning, and there is a smell of burning hair and feathers; The ash can not keep the original fiber shape, but it is amorphous or spherical shiny black brown crisp pieces, which can be crushed by pressing with your fingers. The ash has a large number and smells of burning.
④ Silk, burning slowly, melts and curls, and shrinks into a ball when burning, with a smell of burning hair; When leaving the flame, it will flash slightly, burn slowly, and sometimes self extinguish; Grey is a dark brown crisp ball, which can be crushed by pressing with your fingers.
⑤ The burning behavior of viscose fiber is basically similar to that of cotton, but the burning speed of viscose fiber is slightly faster than that of cotton fiber, with less ash. Sometimes it is not easy to keep its original shape, and the viscose fiber will emit a slight hissing sound when burning.
⑥ Acetate fiber, with fast burning speed, sparks, melting and burning at the same time, and acrid vinegar smell when burning; Melt and burn while leaving the flame; Grey is black, shiny and irregular, which can be crushed with fingers.
⑦ Copper ammonia fiber, burning fast, non melting, non shrinking, with the smell of burning paper; Leave the flame and continue to burn rapidly; The ash is light gray or gray white.
⑧ Nylon, when it is close to the flame, causes the fiber to shrink. After contacting the flame, the fiber quickly shrinks and melts into a transparent colloidal substance with small bubbles.
⑨ Acrylic fiber, melting and burning at the same time, burning fast; The flame is white, bright and powerful, sometimes slightly black smoke; There is fishy smell or pungent smell similar to burning coal tar; Leave the flame and continue to burn, but the burning speed is slow; The ash is a black brown irregular brittle ball, which is easy to twist with your fingers.
⑩ Vinylon, when burning, the fiber shrinks rapidly, burns slowly, and the flame is very small, almost smokeless; When a large amount of fiber is melted, a large dark yellow flame will be generated with small bubbles; Special odor of calcium carbide gas when burning; Leave the flame and continue to burn, sometimes self extinguishing; The ash is a small black brown irregular fragile bead, which can be twisted with fingers.
⑪ Polypropylene fiber, while crimping, while melting, slowly burning; There are blue bright flames, black smoke, and colloidal substances dripping; Smell similar to burning paraffin; Leave the flame and continue to burn, sometimes self extinguishing; The ash is irregular and hard, transparent, and not easy to twist with fingers.
⑫ Chlorine fiber, difficult to burn; Melt and burn in the flame, emitting black smoke; When leaving the flame, it will be extinguished immediately and cannot continue burning; There is an unpleasant pungent chlorine smell when burning; The ash is an irregular dark brown hard lump, which is not easy to twist with fingers.
⑬ Spandex, close to the flame, first expands into a circle, then shrinks and melts; Melt and burn in the flame, the burning speed is relatively slow, and the flame is yellow or blue; Melt while burning when leaving the flame, and slowly self extinguish; Special pungent smell when burning; Ash is a white adhesive block.
3. Density gradient method
The identification process of density gradient method is as follows: first, prepare density gradient solution by properly mixing two kinds of light and heavy liquids with different densities that can be mixed with each other. Generally, xylene is used as light liquid and carbon tetrachloride is used as heavy liquid. By diffusion, light liquid molecules and heavy liquid molecules diffuse each other at the interface of the two liquids, so that the mixed liquid can form a density gradient solution with continuous changes from top to bottom in the density gradient tube. Use standard density balls to calibrate the density values at each height. Then, the textile fiber to be tested shall be pretreated by degreasing, drying, etc., and made into small balls. The small balls shall be put into the density gradient tube in turn, and the density value of the fiber shall be measured and compared with the standard density of the fiber, so as to identify the type of fiber. Because the density gradient liquid will change with the temperature change, the temperature of the density gradient liquid must be kept constant during the test.
4. Microscopy
By observing the longitudinal morphology of textile fibers under the microscope, we can distinguish the major categories to which they belong; The specific name of the fiber can be determined by observing the cross-sectional morphology of the textile fiber.
5. Dissolution method
For pure textile fabrics, a certain concentration of chemical reagents shall be added to the test tube containing the textile fibers to be identified during identification, and then the dissolution of textile fibers (dissolved, partially dissolved, slightly dissolved, insoluble) shall be observed and carefully distinguished, and the temperature at which they are dissolved (dissolved at room temperature, dissolved by heating, dissolved by boiling) shall be carefully recorded.
For the blended fabric, it is necessary to split the fabric into textile fibers, then place the textile fibers on the glass slide with concave surface, unfold the fibers, drop chemical reagents, and observe under the microscope to observe the dissolution of component fibers and determine the fiber type.
Because the concentration and temperature of chemical solvent have obvious influence on the solubility of textile fiber, the concentration and temperature of chemical reagent should be strictly controlled when identifying textile fiber by dissolution method.
6. Reagent coloring method
Reagent dyeing method is a method to quickly identify textile fiber varieties according to the different dyeing properties of various textile fibers to certain chemical reagents. Reagent coloring method is only applicable to non dyed or pure spun yarns and fabrics. Colored textile fibers or textile fabrics must be progressiveness decolorized.
7. Melting point method
The melting point method is based on the different melting characteristics of various synthetic fibers. The melting point is measured by the melting point meter, so as to identify the varieties of textile fibers. Most synthetic fibers do not have an exact melting point. The melting point of the same synthetic fiber is not a fixed value, but the melting point is basically fixed in a narrow range. Therefore, the type of synthetic fiber can be determined according to the melting point. This is one of the methods to identify synthetic fibers. This method is not simply used, but is used as an auxiliary method for verification after preliminary identification. It is only applicable to pure synthetic fiber fabrics without melt resistance treatment.
Post time: Oct-17-2022