In
industrial chemistry, a stabilizer or stabiliser is a chemical that is used to prevent
degradation.
File:BigPhosphite31570-04-4.png, Tris(2,4-di-tert-butylphenyl)phosphite
Tris(2,4-di-tert-butylphenyl)phosphite is an organophosphorus compound with the formula C4H9)2C6H3Osub>3P. This white solid is a widely used stabilizer in polymers where it functions as an antioxidant as well as other roles. The compound is a ...
is a widely used stabilizer in polymers.
File:HALSgeneric.png, Partial structure of typical hindered amine light stabilizers, widely used to protect automotive paints from degradation by UV-light.
File:Salpn.png, Salpn is a typical metal deactivator used as a fuel additive to suppress oxidation processes that lead to gums and solids. Metal deactivators like salpn form stable complexes with the metals, suppressing their catalytic activity.
Overview
Heat and light stabilizers are added to plastics because they ensure safe processing and protect products against aging and weathering. The trend is towards fluid systems,
pellets, and increased use of masterbatches. There are monofunctional, bifunctional, and polyfunctional stabilizers. In economic terms the most important product groups on the market for stabilizers are compounds based on
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
(calcium-
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic t ...
and organo-calcium),
lead
Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
, and
tin stabilizers as well as liquid and light stabilizers (
HALS,
benzophenone,
benzotriazole).
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
-based stabilizers largely vanished in the last years due to health and environmental concerns.
[Ceresana, Market Study Stabilizers, March 2014, http://www.ceresana.com/en/market-studies/additives/stabilizers/]
Polymers
Some kinds of stabilizers are:
*
antioxidant
Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricants ...
s these prevent
autoxidation
Autoxidation (sometimes auto-oxidation) refers to oxidations brought about by reactions with oxygen at normal temperatures, without the intervention of flame or electric spark. The term is usually used to describe the gradual degradation of organi ...
of materials and come in 3 primary forms.
** Oxygen scavengers (primarily
phosphite esters such as tris(2,4-di-tert-butylphenyl)phosphite) are commonly used during the initial processing of the plastic.
** Persistent
radical scavengers prevent or slow the
photo-oxidation of polymers. Traditionally these are alkylated phenols such as
butylated hydroxytoluene but now also include
hindered amine light stabilizers (HALS)
**
Antiozonants prevents or retards the degradation of polymers caused by
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
(
ozone cracking)
*
sequestrants, forming
chelate complexes and inactivating traces of metal ions that would otherwise act as catalysts
*
ultraviolet stabilizers are used to protect polymers from effects of
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiati ...
radiation and come to 2 main types.
** UV absorbers which essentially act the same way as
sunscreen
Sunscreen, also known as sunblock or sun cream, is a photoprotective topical product for the skin that mainly absorbs, or to a much lesser extent reflects, some of the sun's ultraviolet (UV) radiation and thus helps protect against sunbu ...
s
** Quenchers, which dissipate the radiation energy as heat instead of letting it break chemical bonds; often organic
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
salts, e.g. nickel
phenolates
Paints
*
emulsifier
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...
s and
surfactant
Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, fo ...
s, for stabilization of
emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althou ...
s
Food
In foods, stabilizers prevent spoilage. Classes of food stabilizers include emulsifiers,
thickeners and gelling agents, foam stabilizers, humectants,
anticaking agents, and coating agents.
[Erich Lück, Gert-Wolfhard von Rymon Lipinski "Foods, 3. Food Additives" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2002, Wiley-VCH, Weinheim. ]
See also
*
Corrosion inhibitor
In chemistry, a corrosion inhibitor or anti-corrosive is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy, that comes into contact with the fluid. The effectiveness ...
*
Stabilizers for polymers
References
Chemical kinetics
Chemical compounds
Material protection
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