There are certain technical tests performedfor identifying various fibers. These tests require high technology laboratory equipment and are much more reliable than the non technical fibre tests.Technicals tests require high skilled personnel and technical know how of handling chemicals and their accurate analysis. These tests are very valuable for those fabrics that are a blend of different yarns and also have certain special properties including flame retardance etc.
TYPES OF TECHNICAL TEST
- Microscopic test
- Chemical test
- Microscopic test is a technical test that involves identifying the fabric with the help of a microscope with a magnification of minimum 100 power.
- The test can easily distinguish between fibers.
- The test identifies the natural fibers more easily as compared to man made ones.
- Synthetic fibers are very similar in appearance and the increase in the number of varieties, makes it a little tough to distinguish the fibers even under a microscope.
- It is a single elongated cell. Under the microscope, it resembles a collapsed, spirally twisted tube with a rough surface.
- The thin cell wall of the fiber has from 200 to 400 convolutions per inch.
- Under the microscope, the hair like flax fiber shows several sided cylindrical filaments with fine pointed ends.
- The fiber somewhat resembles a straight, smooth
- Under the microscope , wool’s cross section shows three layers- epidermis, cortex and the medulla.
- It appears somewhat elliptical and triangular in cross section when we see under the microscope.
- It is composed of fibroin, consisting of two filaments, called brin which is held together by sericin.
- Rayon fibers have a glasslike luster under the microscope and appear to have a uniform diameter when viewed longitudinally.
- The cross sectional view has a bulbous or multilobal appearance with indentations.
- These indentations appear as occasional markings or
- The basic microscopic appearance is generally fine ,round, smooth, andtranslucent.
- It is also produced in multilobal cross-sectional types.
- Generally, polyester fibers are smooth and straight and the cross-section is round.
- This general characteristics may be altered to achieve certain characteristics, such
- ACRILAN ACRYLIC: It has a bean-shaped cross section, its longitudinal appearance is straight and smooth.
- ORLON ACRYLIC: It has a flat, nut-shaped cross section.
- CRESLAN ACRYLIC: It has an almost round cross section.
- MOD ACRYLICS: it is of two types verel modacrylic and SEF modacrylic
GLASS: The fiber is smooth, round, translucent, highly lustrous, and quite flexible.
- Chemical tests are another technical means of identifying fibers. But chemical tests are not intended for the general consumers.
- Different types of chemical tests are undertaken to establish the identity of the fibers used.
- These tests give accurate and precise analysis.
- The tests are conducted in research laboratories.
Also known as the Double Barrel Fibre Identification (DBFI), the test is based on the theory that each fibre has its own distinct two- colour reaction when treated with stain.
A fibre will turn to a particular colour in the presence of dilute acetic acid and to some other specific colour when stained in the presence of a mild alkali.
The test involves treating the fibres in certain solvents for identifying them. The technical test is becoming difficult to conduct as most of the manufactured fibres and their blends are chemically similar. There is no individual chemical or solvent test for separating or identifying the fibres in combinations
This technical fibre identification test has the following advantages and limitations
• More reliable than the non technical tests.
• Used for both man made fibres and natural fibres.
• Easily conducted.
• Certain manufacturing and finishing processes like mercerizing, affects the appearance of the fibres under the microscope.
• Very dark coloured fabrics cannot be identified under microscope.
• Dye stuffs must be removed from fabrics.