There are several possibilities to understand what fiber or fibers any textile material (open fibre, yarn, woven or fabric) is made of. In some cases, a single test is enough to understand what fiber the material is made of, but usually the decision made after several different experiments is healthier. Since the tests are simple, they do not take much time.
We can collect the tests made to understand what kind of fiber the textile material is made of, in 5 main groups;
1-Burning test
2-Microscope test
3-Dry distillation
4-Painting test
5-Tests with chemical solvents
1-FIRE TEST
By burning the fiber in a small flame, it is possible to determine whether the fiber used is vegetable, animal or synthetic, by examining the way it burns, its smell during combustion and the residues left at the end of combustion. It can even be said that it is definitely that fiber as a result of some burns. However, the result of the burning test may be affected by the dye, finishing and finishing materials on the textile material. For this reason, these substances are removed without damaging the textile fiber.
The threads removed from the sample fabric are burned. The type of yarn is determined by examining the way the yarn burns in the flame, the smoke and smell, and the residue left as a result of combustion.
Animal fibers (wool, silk, regenerated protein):
It catches fire immediately, slowly leaving a black brittle ash. It smells like burnt hair.
Vegetable fibers (cotton, viscose):
It catches fire immediately and burns quickly. leaves a grayish ash. It smells like burnt paper.
Mineral fibers (asbestos, glass fibers):
They melt into beads. They do not change in the combustion test. It is odorless.
Acetate fibers (diacetate, triacetate):
It catches fire immediately and shrinks to form a black body. It smells like acetic acid.
Polyamide fibers :
In the face of the flame, it first melts and then burns, leaving a yellow-brown residue that does not break easily. The smoke is usually white. It smells mild but not sharp hair smell.
Polyester fibers (PES):
In the face of the flame, it first melts and then burns. Its smoke is black and sooty. It has a sweet aromatic pungent odour.
Polyacrylonitrile fibers (PAC) (Acrylic):
It catches fire quickly, does not extinguish on its own, burns by melting, its residue is hard. Its smoke is black and sooty. It smells of burning meat.
Polyethylene fibers (PE):
It melts first. After it burns, a brown residue remains. Its smoke is white. It smells like a burning candle.
Polyvinylchloride (PVC):
It melts first, then burns, emits white smoke after burning black smoke. A black brittle residue remains. It smells like HCl.
Polypropylene (PP) :
It melts, does not burn, a yellow-brown residue remains. Its smoke is white. Smells like a burning candle
2-MICROSCOPE TEST
Microscope is widely used in examining the structure of the fibers, measuring the length and diameter widths, determining the shape and degree of damage to the fiber by bacteria, fungi and other pests in fiber identification and grading.
A wide variety of microscopes can be used for these determinations. But the basics are all the same. The main properties of various textile fibers under the microscope are as follows.
Cotton
Cross-sections of cotton fibers appear as kidneys or beans. In the middle part of the fiber, there is a channel called the lumen along the fiber. The cellulosic wall around this channel is composed of very thin and thread-like fibrils. It is also seen that cotton fibers contain some twists. The cell walls of the mature cotton fiber are thick and the number of folds is high. The opposite is true for immature cotton fiber. In mercerized cotton fibers, on the other hand, when the fibers swell, they almost flatten and become close to a cylinder.
Wool
It appears as a flat cylinder under the microscope. The fiber surface consists of flakes sitting on top of each other. In the middle of the rough faces, there is a space called the medula. The cross section of the wool fiber is oval or round.
ketene
It is made up of cells coming together. The faces of these cells contain signs at certain intervals, they are regular. Their section is similar to a polygon.
Viscous
The fibers are straight. There are fine lines on the fiber surface. Its cross-section looks like a sawtooth.
Silk
It consists of two separate fibers stuck together. While raw, its surface is uneven. After cooking, the separated fibers are transparent and have a smooth surface. Its cross section is similar to a triangle.
Cellulose Acetate
The filaments are corrugated flat rods. Its cross-sections are like clover leaves and its slices are irregular.
Polyamide
It is round in cross section, similar in appearance to a straight bar.
Polyester
The filaments have the appearance of straight rods. Stapel fiber is crimped. Its cross section is circular.
polyacrylic
It is smooth, twisted or broadly striated. Its cross section is round bean shaped .
3-DRY DESTILATION TEST
The basis of the dry distillation test is to determine the pH values of the gases released by the dry distillation of the textile fiber. For this purpose; fiber samples are placed in test tubes and heated slowly in the flame. When gas starts to come out of the fiber sample, the pH paper is wetted and held on the tube. The colors that appear as a result of the reaction of the gas on the pH paper provide fiber definition.
Textile fibers emit a peculiar gas. On the other hand, since protein-based natural and regenerated protein fibers other than silk fibers contain cystine groups, they produce hydrogen sulfide gas as a result of dry distillation. The results obtained can be confirmed by holding wet lead acetate paper over the tube mouth. Synthetic fibers produce neutral gases when dry distilled. However, it is observed that they emit acidic or basic gases when heating is continued for a long time.
4-PAINTING TEST
Since the dyeing properties of the fibers differ, they are dyed in different colors and shades with special test dyestuffs. You can get an idea about the type of fiber analyzed according to the color and tone of the color charts or comparison dyeings at the end of the test dyeing.
But it also has some drawbacks. The dyeability properties of the fibers are very sensitive. The same type of fiber can be dyed in different tones or even colors depending on the region or brand it is grown in, and the finishing process it sees. Another drawback is that the dyestuff must be removed before the analysis of colored materials.
5-TESTS WITH CHEMICAL SOLVENTS
Fibers can be distinguished according to their behavior in chemicals and whether they dissolve or not. If the chemical that dissolves the sample is identified, the fiber can also be recognized. The chemical substances they dissolve for various fibers are given below.
Cotton
· Completely soluble in 80% H2SO4 in cold and hot temperatures. · Insoluble in concentrated HCl. Soluble in bleached cotton copperammonium hydroxide.
Wool
It dissolves immediately in concentrated HCl at 34°C. It is hot soluble in 80% H2SO4. It dissolves in hot in formic acid/zinc chloride solution. It is dissolved in 5% sodium hypochlorite solution at 20°C for 20 minutes. It dissolves in. It dissolves when boiled with 2% lye or potash.
Silk
It dissolves when boiled with 2% lye or potash. It dissolves in 5% sodium hypochlorite at 20°C in 20 minutes. It dissolves in 75% H2SO4 solution at 50°C. Deserialized silk dissolves in formic acid/zinc chloride solution at 40°C.
viscose
It is soluble in 80% H2SO4. It is hot soluble in formic acid-zinc chloride.
Acetate
Soluble in 100% acetone and 80% acetone. Soluble in concentrated HCl at 35°C. Cold soluble in 80% H2SO4. It is soluble in meta-cresol. It is soluble in boiling dioxane. It is soluble in glacial acetic acid. Dimethylformamide is also soluble in heat and cold. It is soluble in formic acid/zinc chloride solution.
Cellulosetriacetate
Soluble in cold methylenechloride.Soluble in 100% acetone. It is soluble in glacial acetic acid. It is soluble in dimethylformamide in hot. It is soluble in formic acid/zinc chloride solution. It is soluble in boiling, concentrated H2SO4. It is soluble in cold chloroform.
Polyamide (nylon)
It is cold soluble in 80% H2SO4. It is soluble in meta-cresol and phenol at room temperature. It is soluble in 85% boiling formic acid. It is soluble in 20% HCl at room temperature. It is soluble in boiling 96% acetic acid.
Polyacrylonitrile
It is soluble if boiled in 70% ammonium thiocyanide for 10 minutes. It is soluble if boiled in dimethylformamide. Polyurethane, Lycra; It is cold soluble in concentrated sulfuric acid. It is soluble in boiling dimethylformamide. It is soluble in boiling formic acid.
Cam
It is insoluble in solvents. It is abraded with hydrofluoric acid.
Asbestos
It is insoluble in solvents.
Polyolefin (polyethylene, polypropylene)
It dissolves in xylene at boiling point.
polyvinylchloride
Soluble in tetrahydrofuran. Soluble with boiling dimethylformamide
Due to the differences in the morphology and chemical structure of the fibers, their solubility in various solvents is different. By using the solubility feature, fiber types are determined by the solubility test.
