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Degradation of polymers by oxygen reactive species formed from photoreactions of oxygen

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Polymer Photodegradation

Abstract

Being an endothermic allotrope of oxygen, ozone (O3) may serve as a precursor for reactive oxygen species such as atomic oxygen (\( {}^1{O_2} \)) and singlet oxygen (l02). The absorption of light by ozone consists of three bands: 200–320 nm (Hartley band), 300–360 nm (Huggins band) and 440–850 nm (Chappuis band) [352]. The primary photochemical processes differ considerably in each of these bands. The quantum yield of ozone photolysis at 254 nm is almost unity (\( \phi = 0.9\pm 0.2 \)). The main photoproducts are atomic oxygen (O) and singlet oxygen \( {}^1{O_2}({}^1{\Delta_g}) \), according to the reaction [704,990,1628]:

$$ {O_3}\xrightarrow{{hv}}O({}^1D) + {}^1{O_2}(1{\Delta_g}) $$
((7.1))
$$ O({}^1D) + {O_3} \to 2O + {O_2} $$
((7.2))
$$ {}^1{O_2}({}^1{\Delta_g}) + {O_3} \to O + 2{O_2} $$
((7.3))

The quantum yield of ozone decomposition at 334 is \( \phi = 4 \), indicating that one of the products must be excited species capable of decomposing O3 further. The primary process of O3 photolysis at 334 nm occurs according to the reactions [1628]:

$$ {O_3}\xrightarrow{{hv}}O({}^3P) + {}^1{O_2}({}^1{\Delta_g}or{}^3\sum\nolimits_g^{ + } {} ) $$
((7.4))
$$ O({}^3P) + {O_3} \to {O_2} + {O_2} $$
((7.5))
$$ {}^1{O_2}({}^1{\Delta_g}or{}^3\sum\nolimits_g^{ + } {} ) + {O_3}\xrightarrow{{hv}}O({}^3P) + 2{O_2} $$
((7.6))

From this mechanism, the overall quantum yield of O3 decomposition is \( \phi = 4 \).

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© 1995 Springer Science+Business Media Dordrecht

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Rabek, J.F. (1995). Degradation of polymers by oxygen reactive species formed from photoreactions of oxygen. In: Polymer Photodegradation. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-1274-1_7

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  • DOI: https://doi.org/10.1007/978-94-011-1274-1_7

  • Publisher Name: Springer, Dordrecht

  • Print ISBN: 978-94-010-4556-8

  • Online ISBN: 978-94-011-1274-1

  • eBook Packages: Springer Book Archive

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