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Photodegradation and photostabilization of polymers, especially polystyrene: review.

Yousif E, Haddad R - Springerplus (2013)

Bottom Line: Almost all synthetic polymers require stabilization against adverse environmental effects.It is necessary to find a means to reduce or prevent damage induced by environmental components such as heat, light or oxygen.A profound knowledge of degradation mechanisms is needed to achieve the goal.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, College of Science, Al-Nahrain University, Baghdad, Iraq.

ABSTRACT
Exposure to ultraviolet (UV) radiation may cause the significant degradation of many materials. UV radiation causes photooxidative degradation which results in breaking of the polymer chains, produces free radical and reduces the molecular weight, causing deterioration of mechanical properties and leading to useless materials, after an unpredictable time. Polystyrene (PS), one of the most important material in the modern plastic industry, has been used all over the world, due to its excellent physical properties and low-cost. When polystyrene is subjected to UV irradiation in the presence of air, it undergoes a rapid yellowing and a gradual embrittlement. The mechanism of PS photolysis in the solid state (film) depends on the mobility of free radicals in the polymer matrix and their bimolecular recombination. Free hydrogen radicals diffuse very easily through the polymer matrix and combine in pairs or abstract hydrogen atoms from polymer molecule. Phenyl radical has limited mobility. They may abstract hydrogen from the near surrounding or combine with a polymer radical or with hydrogen radicals. Almost all synthetic polymers require stabilization against adverse environmental effects. It is necessary to find a means to reduce or prevent damage induced by environmental components such as heat, light or oxygen. The photostabilization of polymers may be achieved in many ways. The following stabilizing systems have been developed, which depend on the action of stabilizer: (1) light screeners, (2) UV absorbers, (3) excited-state quenchers, (4) peroxide decomposers, and (5) free radical scavengers; of these, it is generally believed that excited-state quenchers, peroxide decomposers, and free radical scavengers are the most effective. Research into degradation and ageing of polymers is extremely intensive and new materials are being synthesized with a pre-programmed lifetime. New stabilizers are becoming commercially available although their modes of action are sometimes not thoroughly elucidated. They target the many possible ways of polymer degradation: thermolysis, thermooxidation, photolysis, photooxidation, radiolysis etc. With the goal to increase lifetime of a particular polymeric material, two aspects of degradation are of particular importance: Storage conditions, and Addition of appropriate stabilizers. A profound knowledge of degradation mechanisms is needed to achieve the goal.

No MeSH data available.


Related in: MedlinePlus

Quinones retard oxidation process.
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Related In: Results  -  Collection

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Fig37: Quinones retard oxidation process.

Mentions: Oxidizing agents, e.g. quinones which have been shown to be able to retard oxidation, can function as antioxidants (via a chain breaking acceptor process), if they can compete with oxygen for alkyl radicals Watson (1953), as shown in the following equation see FigureĀ 37.Figure 37


Photodegradation and photostabilization of polymers, especially polystyrene: review.

Yousif E, Haddad R - Springerplus (2013)

Quinones retard oxidation process.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4320144&req=5

Fig37: Quinones retard oxidation process.
Mentions: Oxidizing agents, e.g. quinones which have been shown to be able to retard oxidation, can function as antioxidants (via a chain breaking acceptor process), if they can compete with oxygen for alkyl radicals Watson (1953), as shown in the following equation see FigureĀ 37.Figure 37

Bottom Line: Almost all synthetic polymers require stabilization against adverse environmental effects.It is necessary to find a means to reduce or prevent damage induced by environmental components such as heat, light or oxygen.A profound knowledge of degradation mechanisms is needed to achieve the goal.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, College of Science, Al-Nahrain University, Baghdad, Iraq.

ABSTRACT
Exposure to ultraviolet (UV) radiation may cause the significant degradation of many materials. UV radiation causes photooxidative degradation which results in breaking of the polymer chains, produces free radical and reduces the molecular weight, causing deterioration of mechanical properties and leading to useless materials, after an unpredictable time. Polystyrene (PS), one of the most important material in the modern plastic industry, has been used all over the world, due to its excellent physical properties and low-cost. When polystyrene is subjected to UV irradiation in the presence of air, it undergoes a rapid yellowing and a gradual embrittlement. The mechanism of PS photolysis in the solid state (film) depends on the mobility of free radicals in the polymer matrix and their bimolecular recombination. Free hydrogen radicals diffuse very easily through the polymer matrix and combine in pairs or abstract hydrogen atoms from polymer molecule. Phenyl radical has limited mobility. They may abstract hydrogen from the near surrounding or combine with a polymer radical or with hydrogen radicals. Almost all synthetic polymers require stabilization against adverse environmental effects. It is necessary to find a means to reduce or prevent damage induced by environmental components such as heat, light or oxygen. The photostabilization of polymers may be achieved in many ways. The following stabilizing systems have been developed, which depend on the action of stabilizer: (1) light screeners, (2) UV absorbers, (3) excited-state quenchers, (4) peroxide decomposers, and (5) free radical scavengers; of these, it is generally believed that excited-state quenchers, peroxide decomposers, and free radical scavengers are the most effective. Research into degradation and ageing of polymers is extremely intensive and new materials are being synthesized with a pre-programmed lifetime. New stabilizers are becoming commercially available although their modes of action are sometimes not thoroughly elucidated. They target the many possible ways of polymer degradation: thermolysis, thermooxidation, photolysis, photooxidation, radiolysis etc. With the goal to increase lifetime of a particular polymeric material, two aspects of degradation are of particular importance: Storage conditions, and Addition of appropriate stabilizers. A profound knowledge of degradation mechanisms is needed to achieve the goal.

No MeSH data available.


Related in: MedlinePlus