موانع الاكسدة المضافة للزيوت المعدنية

Antioxidant

مجموعة تكنولاب البهاء جروب

عميد دكتور

بهاء بدر الدين محمود

استشارى كيميائى

01229834104

Model of the antioxidant metabolite glutathione.

The yellow sphere is the redox-active sulfur atom that provides antioxidant activity, while the red, blue, white, and dark grey spheres represent oxygen, nitrogen, hydrogen, and carbon atoms, respectively.

An antioxidant is a molecule that inhibits the oxidation of other molecules.

Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent.

Oxidation reactions can produce free radicals.

In turn, these radicals can start chain reactions.

When the chain reaction occurs in a cell, it can cause damage or death to the cell.

Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions.

They do this by being oxidized themselves, so antioxidants are often reducing agents such as thiols, ascorbic acid, or polyphenols.

[1]
Antioxidants are important additives in gasoline.

These antioxidants prevent the formation of gums that interfere with the operation of internal combustion engines.

[2]

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Industrial uses

Antioxidants are frequently added to industrial products.

A common use is as stabilizers in fuels and lubricants to prevent oxidation, and in gasolines to prevent the polymerization that leads to the formation of engine-fouling residues.

In 2007, the worldwide market for industrial antioxidants had a total volume of around 0.88 million tons.

They are widely used to prevent the oxidative degradation of polymers such as rubbers, plastics and adhesives that causes a loss of strength and flexibility in these materials.

Polymers containing double bonds in their main chains, such as natural rubber and polybutadiene, are especially susceptible to oxidation and ozonolysis.

They can be protected by antiozonants. Solid polymer products start to crack on exposed surfaces as the material degrades and the chains break.

The mode of cracking varies between oxygen and ozone attack, the former causing a "crazy paving" effect, while ozone attack produces deeper cracks aligned at right angles to the tensile strain in the product.

Oxidation and UV degradation are also frequently linked, mainly because UV radiation creates free radicals by bond breakage.

The free radicals then react with oxygen to produce peroxy radicals which cause yet further damage, often in a chain reaction.

Other polymers susceptible to oxidation include polypropylene and polyethylene.

The former is more sensitive owing to the presence of secondary carbon atoms present in every repeat unit.

Attack occurs at this point because the free radical formed is more stable than one formed on a primary carbon atom.

Oxidation of polyethylene tends to occur at weak links in the chain, such as branch points in low density polyethylene.

Fuel additive Components[251] Applications]
AO-22

N,N'-di-2-butyl-1,4-phenylenediamine

Turbine oils, transformer oils, hydraulic fluids, waxes, and greases
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AO-24

N,N'-di-2-butyl-1,4-phenylenediamine

Low-temperature oils
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AO-29

2,6-di-tert-butyl-4-methylphenol

Turbine oils, transformer oils, hydraulic fluids, waxes, greases, and gasolines

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AO-30

2,4-dimethyl-6-tert-butylphenol

Jet fuels and gasolines, including aviation gasolines

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AO-31

2,4-dimethyl-6-tert-butylphenol

Jet fuels and gasolines, including aviation gasolines

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AO-32

2,4-
dimethyl-6-tert-butylphenol and 2,6-di-tert-butyl-4-methylphenol

Jet fuels and gasolines, including aviation gasolines
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AO-37

-2,6
di-tert-butylphenol

Jet fuels and gasolines, widely approved for aviation fuels

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