Optical brighteners , optical brighteners ( OBAs ), fluorescent pollutants ( FBA ), or fluorescent bleaching agents ( FWAs ), are light-absorbing chemical compounds in the ultraviolet and violet regions (typically 340-370Ã,nm) of the electromagnetic spectrum, emit in the blue region (usually 420-470 nm) by fluorescence. Fluorescent emission is a brief period of light emission by fluorophore, unlike phosphorescent, long-lived. These additives are often used to enhance the appearance of cloth and paper colors, causing a "whitening" effect; they make the intrinsic yellow/orange material less visible, compensating for the blue and violet light deficits reflected by the material, with optical emissions of blue and purple fluorophore.
Video Optical brightener
Properti
The most common class of compounds with this property is stylbene, for example 4.4? -diamino-2,2? -stilbenedisulfonic acid. Older, non commercial, fluorescent chemicals include umbelliferone, which absorbs the UV part of the spectrum and relays it back to the blue part of the visible spectrum. White surfaces that are treated with optical brightener can emit a more visible light than the glowing light above it, making it appear brighter. The blue light emitted by the brightener compensates for the diminishing blue color of the treated material and changes the hue away from yellow or brown and toward white.
About 400 types of brightener are listed in the Color Index, but fewer than 90 are commercially produced, and only a handful are commercially important. In general, C.I. FBA numbers can be assigned to certain substances, however, some are duplicated, because manufacturers are filing index numbers when they produce them. Global OBA production for paper, textile, and detergent is dominated by only a few in- and tetra-sulfonated triazole-stilbenes and stilbene-biphenyl di-sulphonated derivatives. Stilbene derivatives may fade on prolonged exposure to UV light, due to the formation of optically inactive cis-stilbenes. They are also degraded by oxygen in the air, like most dye dyes. All brighteners have expanded conjugation and/or aromatisity, allowing for movement of electrons. Some non-stilbene brighteners are used in more permanent applications such as whitening synthetic fibers.
Brighteners can be "pushed" by the addition of certain polyols, such as high molecular weight polyethylene glycols or polyvinyl alcohols. These additives increase visible emission of blue light significantly. The enlightenment can also be "quenched". Excess brightener will often cause a greening effect when emissions start to look above the blue region in the visible spectrum.
Maps Optical brightener
General use
Brighteners are generally added to detergents to make clothes look cleaner. Usually cleaned laundry looks yellowish, which consumers do not like. Optical brighteners have replaced bluing previously used to produce the same effect.
Brightener is used in many papers, especially high-brightness paper, which results in a very pale appearance under UV light. Paper brightness is usually measured at 457 n nm, both within the range of fluorescent brighteners activity. Paper used for banknotes does not contain optical brighteners, so a common method for detecting false records is to check for fluorescence.
Optical brighteners are also found used in cosmetics. One of the applications is a formula for washing and conditioning gray or blond hair, where brightener can not only increase luminance and hair sparkle, but can also improve dull, yellowish color without darkening the hair. Some sophisticated face and eye powders contain optical brightener microspheres that brighten dark or dark areas of the skin, such as "tired eyes".
The side effect of textile optical bleaching is making the treated fabric more visible with Night Vision Devices than not being treated. This may or may not be desirable for military or other applications. Optically bright papers are often useless in photography or art applications, as whiteness diminishes over time.
End use of optical brighteners including:
- Bleach detergent (not bluing agent)
- Paper brightening (internal or in layers)
- Fiber bleaching (internal, added to melted polymer)
- Textile bleaching (externally, added to finished fabric)
- Color proofing or lightening additives in advanced cosmetic formulas (shampoo, conditioner, eye makeup)
Security
Some brighteners can cause allergic reactions when in contact with the skin, depending on the individual.
References
Source of the article : Wikipedia
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