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 OBA’s exhaust on cotton, wool and silk, cationic OBA’s exhaust on acrylic and certain polyesters and non-ionic OBA’s are exhaust on all synthetics.

 

Application of Optical BrightenersOptical 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.

 

Drawbacks of Optical Brighteners

• Can cause allergic reactions.
• Toxic for fishes if discharged in waters.
• They are not readily biodegradable.