How to identify the fiber present in a textile material?

Fiber identification is studied in order to understand the properties and characteristics each fiber possesses and also helps us to categorize various available fibers according to their similarity in one or another class. There are several parameters that are considered before putting a fiber into a certain category. These include physical properties, chemical composition, performance, and care procedure. Let us now try to understand some tests that are performed to identify fibers.

• Microscopic Test: Each fiber whether being natural or synthetic in nature has certain specific features that help in their identification. The microscopic examination involves viewing the longitudinal section of the certain fiber under the microscope.

For example, the longitudinal section of cotton has a ribbon-like structure with convolutions at irregular intervals.

• Feeling Test: This test deals with the tactile ability of fibers. It involves touching a fabric and feeling its composition.

For example, wool fabrics will feel warm when touched because of the heat generated by wool while cotton and other plant-based fibers feel cool on touch since they are composed of cellulose of wood pulp.

However, the feeling test has a drawback that beginners or amateur individuals will find it difficult to predict the fiber composition just by touch. And so, it requires years of experience for such accurate prediction.

• Burning Test: It involves studying the behavior of fiber under the following conditions: 1. fiber when approaching flame 2. Inflame 3. Removed from flame 4. Odor 5. Residue. This test is a simple test to identify the family (cellulosic, protein, or synthetic) of a fiber.

Firstly, cellulosic fibers burn readily in the flame and continue to burn with an afterglow after which they self-extinguish. Their odor is similar to burning paper because of cellulose composition and leaves a grey, fluffy ash, and easily crushable residue.

Protein fibers, on the other hand, burn slowly and curl away from the approaching flame. They smell of burning hair and leave behind a black bead-like residue which is easy to crush.

Lastly, the synthetics fuse and melt away from flame and give a sputtering black sooty flame with an odor that resembles chemicals.
Also, the burning test has certain limitations i.e. fabric composed of two different textile polymers cannot be identified. For example, cotton polyester blend.

Thus, a burning test helps to determine the fiber content.

• Chemical Test: These tests involve the use of certain chemicals and are not meant to be used by the general population. Different types of chemical tests are performed to the identity of the fiber composition. The results obtained from these tests are reliable and accurate.

Stain Test: This test is based on the fact that each fiber has a different two-color reaction when treated with a stain. The Stain test is also called the Double Barrel fiber Identification (DBFI). Thus, a fiber will show a specific color when stained with either dilute acetic acid or mild alkali.

Solvent Test: In this test, fibers are exposed or treated with various solvents such as sulphuric acid, sodium hydroxide, etc to identify their composition. For instance: Nylon fiber dissolves readily in 85% of formic acid at room temperature and this confirms that the given fiber is nylon. Similarly, each fiber has a specific solvent in which it dissolves.

Thus, the identification of fibers helps us to associate certain characteristics to each fiber and contribute towards a suitable selection of fiber when developing a certain product.