Fiber Identification System

Microscopic Identification

Examination of longitudinal and cross-sectional views of a fiber at 100 to 500  agnifications gives detailed information with regard to the surface morphology of the fiber. Positive
identification of many natural fibers is possible using the microscope, but positive identification of man-made fibers is more difficult due to their similarity in appearance and due to the fact that spinning techniques and spinneret shape can ~adically alter the gross morphological structure of the fiber.

Sol ubil ity

The chemical structure of polymers in a fiber determines the fiber's basic solubility characteristics, and the effect of solvents on fibers can aid in the general fiber classification. Various classification schemes involving solubility have been developed to separate and identify fibers.

Heating and Burning Characteristics

The reaction of fibers to heat from an open flame is a useful guide in identification of fibers. When thermoplastic fibers are brought close to a flame, they will melt, fuse, and shrink, whereas nonthermoplastic fibers will brown, char, or be unaffected by the flame. On contact with an open flame, fibers of organic polymers will ignite and burn. The nature of the burning reaction is characteristic of the chemical structure of the fiber.On removal from the flame, fibers will either self-extinguish or continue to burn. The odor of gases coming from the decomposing fibers and the nature of any residual ash are characteristic of the fibrous polymer being burned.

Density or Specific Gravity

Fiber density may be used as an aid in fiber identification. Fiber density may be determined by using a series of solvent mixtures of varying density or specific gravity. If the specific gravity of the fiber is greater than that of the liquid, the fiber specimen will sink in the liquid . Conversely, if the specific gravity of the fiber is less than that of the liquid, the fiber specimen will float. Thereby an approximate determination of fiber density may be made.

Staining

Fibers have differing dyeing characteristics and affinities dependent on the chemical and morphological structure of the fiber. Prepared dye mixtures containing dyes of differing affinities for various fiber types have been used extensively as identification stains for undyed fabrics. Since some fiber types may dye to similar shades with these dye mixtures,
two or more stains usually must be used to confirm the fiber content. Staining is effective only for previously undyed fibers or for fibers where the dye is stripped from the fiber prior to staining.
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