An antiozonant, also known as anti-ozonant, is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

that prevents or retards damage caused by

ozone Ozone () (or trioxygen) is an Inorganic compound, 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 , break ...

. The most important antiozonants are those which prevent degradation of

elastomer An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus (E) and high failure strain compared with other materials. The term, a portmanteau of ''ela ...

s like

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...

. A number of research projects study the application of another type of antiozonants to protect plants as well as salmonids that are affected by the chemicals.

Effect of ozone

Many elastomers are rich in unsaturated double bonds, which can react with ozone present in the air in process known as

ozonolysis In organic chemistry, ozonolysis is an organic reaction where the Saturated and unsaturated compounds, unsaturated bonds are Bond cleavage, cleaved with ozone (). Multiple carbon–carbon bond are replaced by carbonyl () groups, such as aldehydes ...

. This reaction breaks the polymer chains, degrading the mechanical properties of the material. The most obvious effect of this is cracking of the elastomer (ozone cracking), which is exacerbated by mechanical stress. The rate of degradation is effected both by the chemical structure of the elastomer and the amount of ozone in the environment. Elastomers which are rich in double bonds, such as

natural rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...

, polybutadiene,

styrene-butadiene Styrene-butadiene or styrene-butadiene rubber (SBR) describe families of synthetic rubbers derived from styrene and butadiene (the version developed by Goodyear is called Neolite). These materials have good abrasion resistance and good aging ...

rubber and

nitrile rubber Nitrile rubber, also known as nitrile butadiene rubber, NBR, Buna-N, and acrylonitrile butadiene rubber, is a synthetic rubber derived from acrylonitrile (ACN) and butadiene. Trade names include Perbunan, Nipol, Krynac and Europrene. This rubber is ...

are the most sensitive to degradation, whereas

butyl rubber Butyl rubber, sometimes just called butyl, is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as "PIB" or polyisobutene, (C4H8)n, is the homop ...

, polychloroprene,

EPDM EPDM rubber (ethylene propylene diene monomer rubber) is a type of synthetic rubber that is used in many applications. EPDM is an M-Class rubber under ASTM standard D-1418; the ''M'' class comprises elastomers with a saturated and unsaturated co ...

and Viton are more resistant.

Ground-level ozone Ground-level ozone (), also known as surface-level ozone and tropospheric ozone, is a trace gas in the troposphere (the lowest level of the atmosphere of Earth, Earth's atmosphere), with an average concentration of 20–30 parts per billion by vo ...

is naturally present, but it is also a product of

smog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odour. The word was then inte ...

and thus degradation is faster in areas of high air pollution. All of these factors make vehicle

tires A tire (North American English) or tyre (Commonwealth English) is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface over w ...

particularly vulnerable, as they contain a high level of unsaturated groups, operate in areas prone to air pollution and are subjected to significant mechanical stresses.

Protection of elastomers

Antiozonants are used as

additive Additive may refer to: Mathematics * Additive function, a function in number theory * Additive map, a function that preserves the addition operation * Additive set-function see Sigma additivity * Additive category, a preadditive category with fin ...

s in tire manufacturing to retard the effects of ozone. The most common antiozonants for elastomers are ''N'',''N''′-substituted ''p''-phenylenediamines (PPD) which can be categorized in three types: * Dialkyl ''p''-Phenylenediamines, such as N,N'-Di-2-butyl-1,4-phenylenediamine * Alkyl-aryl ''p''-Phenylenediamines, such as 6PPD or IPPD * Diaryl ''p''-Phenylenediamines, like DPPD Other classes include: * Styrenated phenol (SPH), styrenated and alkylated phenol (SAPH) * Hydrocarbon waxes which create a surface barrier, preventing contact with ozone:

paraffin wax Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and melting poi ...

, microcrystalline wax.

Protection of plants

For the protection of plants like

winter wheat Winter wheat (usually ''Common wheat, Triticum aestivum'') are strains of wheat that are planted in the autumn to germinate and develop into young plants that remain in the vegetative phase during the winter and resume growth in early spring. C ...

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

{{Cite journal, last1=Singh, first1=Aditya Abha, last2=Chaurasia, first2=Meenakshi, last3=Gupta, first3=Vaishali, last4=Agrawal, first4=Madhoolika, last5=Agrawal, first5=S. B., date=May 2018, title=Responses of Zea mays L. cultivars 'Buland' and 'Prakash' to an antiozonant ethylene diurea grown under ambient and elevated levels of ozone, url=http://link.springer.com/10.1007/s11738-018-2666-z, journal=Acta Physiologiae Plantarum, language=en, volume=40, issue=5, pages=92, doi=10.1007/s11738-018-2666-z, bibcode=2018AcPPl..40...92S , s2cid=13832708, issn=0137-5881, url-access=subscription Ethylene diurea (EDU) has been used successfully as antiozonant.

References

External links

Review of antiozonants
(TheFreeLibrary) Antioxidants Plastics additives

Effect of ozone

Protection of elastomers

Protection of plants

See also

References

External links