With the continuous progress of textile production technology, more and more new fibers have become the raw materials of textiles, which brings about the problem of identifying fibers for textiles. Commonly used fiber identification methods include microscope observation method, combustion method, reagent color development method, dyeing method, dissolution method, etc.

1. Microscope observation method

Longitudinal sheets and cross-sectional slices of the fibers were made, and the longitudinal and transverse morphology of the fibers were observed under a microscope, and the fibers were identified according to the differences in morphological characteristics, as shown in Table 1.

Table 1 Morphological characteristics of various fibers

2. Combustion method

Different fibers have different flames, smoke, odors, residues, etc. during the combustion process. Therefore, the fiber types can be distinguished according to the characteristics of the fibers during and after combustion, as shown in Table 2.

Table 2 Characteristics of various fibers during and after combustion

3. Reagent chromogenic method

Due to the different structures of various fibers, the coloring reactions to iodine and potassium iodide solutions are different. The fibers can be identified by observing the color and swelling of the fibers after the action of the reagents. This identification only applies to white fibers, and colored fibers can only be tested after they have been faded. Reagent preparation: Dissolve 20 grams of iodine in 100 ml of saturated potassium iodide solution, mix thoroughly and then soak the fiber for 1 minute, and judge according to its color after thorough washing, see Table 3.

Table 3 Coloring reaction of various fibers burning to iodine solution

4. Dyeing method

The dyeing method is used to identify fibers, which are mainly distinguished by the different coloring reactions of various fibers to dyes. There are two kinds of dyeing methods: cold dyeing and boiling dyeing. The recipe of the dyeing method is shown in Table 4.

Table 4 Dyeing method formula

Pour the formula in Table 4 into 50 ml of ethanol and stir until dissolved, then dilute to 500 ml with distilled water for later use. The cold dyeing method directly puts the fiber into the solution for dyeing, then rinses the fiber with cold water, squeezes out the water, and observes the color for identification; the boiling dyeing method puts the fiber into the solution for dyeing, boils for 3 minutes, rinses 3 times, and then puts it into 0.1 Rinse in % pancreas plus bleach T solution, squeeze out the water, and observe the color for identification. The dyeing reactions of various fibers are shown in Table 5.

Table 5 Dyeing reactions of various fibers

5. Dissolution method

The dissolution method is the most effective method to identify various fibers. The principle is to use the dissolution characteristics of various fibers in different chemical solvents and different temperatures to determine their varieties.

The fiber to be identified can be put into a test tube, injected with a certain solvent, stirred with a glass rod, and the dissolution of the fiber can be observed. If the amount of fibers is very small, the sample can also be placed in a concave glass slide with a concave surface, dripped with solvent, covered with a glass slide, and observed directly under the microscope. When using the dissolving method to identify fibers, the concentration of the solvent and the heating temperature should be strictly controlled, and attention should be paid to the dissolving speed of the fibers. The use of the dissolution method requires an accurate understanding of various fiber chemical properties, and the inspection procedures are complex. It is more intuitive to use the microscope observation method and the combustion method, but the inspector must have rich practical experience; the reagent color development method and the dyeing method are more complicated to operate and can be used in special circumstances.