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 ~radically alter the gross morphological
structure of the fiber.
Solubility
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.
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.
Very clearly explained , interesting to read.
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