Optical brighteners, also known as optical brightening agents have the
capacity to absorb light in the violet and ultraviolet region of the
electromagnetic spectrum. Subsequently they re-emit light in the blue
region.
The coloring matter, whether it is natural or present as a contaminant in
the fiber is generally decolorized by different bleaching methods. However
the appearance of the textile substrate is somewhat creamish after the
bleaching, therefore chemical treatments are become necessary to neutralize
the yellow tint of the textile fibers.
Optical brightening agents (OBA) are widely used in textiles, paper,
detergents and plastics. The optical brightening effect is obtained by the
addition of light, which means that the amount of light reflected by the
Fluorescent Whitening Agents absorb high energy radiation in the ultraviolet
to violet region (330nm-380nm) on the part of characteristic molecules and
emit lower energy radiation in blue region in visible spectrum
(400nm-450nm), and yields yellow appearance.
OBAs are effective only when the incident light has a significance
proportion (such as daylight) of UV rays. When material treated with OBAs
are exposed to UV black light source, it glows in the dark. Anionic OBAs
exhaust on cotton, wool and silk, cationic OBAs exhaust on acrylic and
certain polyesters and non-ionic OBAs are exhaust on all synthetics.
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Optical brighteners are widely used in
detergents, manufacturing of paper (resulting in their strongly fluorescent
appearance under UV illumination), cosmetics, adhesives, non-destructive
testing of metal parts.