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What are Antiozonants?

8/24/2012 12:50:40 PM | by Anonymous

Antiozonants

Antiozonants are substances that have the ability to prevent or reverse oxidation due to ozone. They are additives that can protect an elastomer from fatigue experienced due to being exposed to atmospheric ozone which makes the elastomer become brittle and form cracks overtime. As ozone contains oxygen which has the ability to deteriorate a rubber, the ozone reacts with the rubber causing damage to the rubber or other forms of elastomers. The prefix “anti” refers to against or opposed to something, and therefore antiozonants are used opposed to ozone. Antiozonants have the ability to overcome the damages that ozone can cause. Mostly, antiozonants are able to provide the protective effect due to a reaction with ozone, therefore their name. An example of a product that is often used as an antiozonant is aromatic amine.

 

Ozone gas can occur naturally or during electric discharges by sparking or corona discharges. Machines that may have moving parts made of rubber and serve the purpose of insulating the material may have static electricity built up within them, putting them at risk of ozone cracking. One example of such a machine can be compressors. Another way that ozone comes about is due to the action of sunlight shining on volatile organic liquids, for example sunlight shining upon gasoline vapor that might be present in the air. This would give rise to ozone being formed which can be harmful to elastomers. An elastomer that would have backbone unsaturation can be the victim of an ozone attack, which would cause the material degrade due to the reaction between the ozone and rubber double bonds.

 

Antiozonants have been in the commercial market since the 1950s and provide people with a solution to overcome ozone cracking. There are either physical or chemical antiozonants. Physical antiozonants, as their name would suggest are physical things that can be used to provide an elastomer with cover from ozone. The antiozonant should be able to provide the rubber surface with an effective barrier against penetration from ozone. Chemical antiozonants work by reacting with ozone, and therefore they should have reactive properties against ozone. As ozone attacks only occur at the surface of the rubber, the antiozonant only needs to be applied on the surface of the rubber to prevent it from getting damaged. The chemical or physical antiozonants should not have any adverse effects on the rubber, especially the chemical antiozonant which contains chemical that can react with the rubber. Along with that the antiozonant should be acceptable economically and should have low or no toxicity.

 

Ozone cracks on rubbers are commonly seen on sidewalls of tires and can pose as serious threat, in extreme cases causing traffic accidents. These issues can be overcome by adding antiozonants over the rubber surface. One common low cost antiozonant which can be used to overcome this is wax. Wax is able to bleed to the surface of the rubber and form a protective layer over it. Waxes are made from petroleum and have two common variations, paraffin and microcrystalline. Regular chemical antiozonants usually compromise of microcrystalline with most chemical antiozonants containing nitrogen. Aside from wax, more sophisticated and specialist chemical can also be used to act as antiozonants. The problems of ozone cracking can recur in unprotected products such as rubber tubing and seals. Traces of ozone cracking can occur in places where one might think it would be impossible for ozone to reach, thus it is important to take care of rubber products in a good way. An alternative to overcoming this problem can be using ozone-resistant rubbers, which have been pre-treated to inhibit cracking.

 

It is important to use antiozonants or other methods to prevent rubber from cracking as when cracks on the rubber occur, they could cause it to look unappealing or cause serious damage to the device. Antiozonants can be a great help in overcoming the problem of ozone cracking.

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