Photodegradation and photostabilization of polymers, especially polystyrene: review

“…degradation of polymers, which include processes such as chain scission, crosslinking and secondary oxidative reactions, and takes place via radical processes , similar to thermal oxidation reactions (Ranby and Rabek 1981; Carlsson et al. 1976; Mc Kellar & Allen 1979; Rnby and Lucki 1980).”

“Photooxidative degradation includes the following steps: (Rabek 1994; Rabek 1974; Guillet 1972a, 1972b).”

“Its hardness, hydrophobic nature and chemical composition cause it to persist in nature without any decomposition for long period of time thus cause environmental pollution Singh and Sharma (2008).”

“from electronically excited carbonyl group to dissolved molecular oxygen Heskins and Guillet (1968). The quenching of [(1)O2] is also necessary for effective stabilization. Nickel chelates have been proven to be very effective quenchers for the excited state of [(1)O2] Schmitt and Hirt (1963).”

“The decomposition of hydroperoxide in polymer to non radical derivatives was first demonstrated Carlsson and Wiles (1974). Many metal complexes of sulphur containing ligands such as dialkylthiocarbonate and dialkylthiophosphate not only decompose hydroxide in PE film but are also effective in UV stabilization (as UV a…”

“Industrially, the yellow discoloration is an important adverse effect of the ageing of polystyrene, e.g. during exposure outdoors (Geuskens et al. 1978a, 1978b; Weir 1978; Lucki and Rnby 1979; Rnby and Lucki 1980).”

“Thus the life of thermoplastics for outdoor applications becomes limited due to weathering Andrady et al. (1998). When polystyrene is subjected to UV irradiation in the presence of air, it undergoes a rapid yellowing and a gradual embrittlement.”

“On exposure to light, these ketone groups absorb photons of appropriate energy, break carbon–carbon bonds, and scission the polymer backbone (Rabek 1995; Feldman 2002) as shown in the Figures 3 and 4 (Grassie and Scott 1985):”

“Alkoxy polymer radicals produced during the photolysis of hydroperoxide groups may decompose by β-scission reaction and to form a cetophenone and chain aliphatic ketone (Figure 23) (Kuzina and Mikhailov 1998; Geuskens et al. 1978a, 1978b).”

“Irradiation of polystyrene by UV. and visible light with wavelength (λ< 400) nm., leads to the formation of radicals whose nature is dependent on the spectral composition of the light and irradiation condition Kuzina and Mikhailov (1993).”

“Figure 3 The β scission in polymer molecule, Grassie and Scott (1985). similar to the abstraction of hydrogen from the polymer molecule:”

“C C C H 1 O 2 C OOH C C (4) (II) The free radical mechanism of oxidation The radical mechanism of photooxidation of polymers proceeds through a chain reaction similar to that for homogeneous liquid phase oxidations Kochi and Wiley (1973), Geuskens & David (1979a, 1979b).”

“In recent years, the use of polymeric materials has rapidly increased but it is well established that rapid photodegradation of these materials is possible when they are exposed to natural weathering (Guillet 1985; Hamid 2000; Rabek 1996; Bottino et al. 2003).”

“Industrially, the yellow discoloration is an important adverse effect of the ageing of polystyrene, e.g. during exposure outdoors (Geuskens et al. 1978a, 1978b; Weir 1978; Lucki and Rnby 1979; Rnby and Lucki 1980).”

“The manufacturers of paints, plastics, contact lenses, and cosmetics have a great interest in offering products that remain unaltered for long periods under conditions of light exposure (Galdi et al. 2010; Pospisil et al. 2006; Bojinov & Grabchev 2005; Goldshtein and Margel 2011), (Figure 1).”

“These are thus key intermediates in the oxidation of polymers Amin et al. (1975).”

“Polystyrene losses its mechanical and tensile properties due to effect of UV light and heat Kiatkamjornwong et al. (1999). UV light induces the production of radicals by oxidation.”

“model compound for HALS), during UV irradiation in the presence of oxygen (air) and radicals (R), produces hindered piperidinoxy radicals according to the reaction 1 Yousif et al. (2011b): Piperindoxy radicals react with alkyl radicals (R) to give a substituted hydroxypiperidine as shown in reaction 2 in Figure 34.”

“The electron spin resonance (ESR) spectra obtained during the UV, irradiation of polystyrene (PS) were interpreted as arise from radicals formed in reaction (8) Cozzen and Fox (1969); Grassie and Weir (1965).”

“General purpose polystyrene is clear and hard which is used in packaging, laboratory ware, and electronics Meenakshi et al. (2002).”

“The type of the radicals formed during polystyrene photodegradation depends on the irradiation wavelength Ranby and Rabek (1975). The movement of polymer macromolecules in the solid state is restricted, but radicals can migrate along the polymer chain until they trapped by other radicals or by impurities.”

“It has the tendency to crystallize very quickly which gives it the favourable properties of high melting temperature and chemical resistance (Saitoh et al. 2003; Gupper and Kazarian 2005) (Figure 9).”

“…degradation of polymers, which include processes such as chain scission, crosslinking and secondary oxidative reactions, and takes place via radical processes , similar to thermal oxidation reactions (Ranby and Rabek 1981; Carlsson et al. 1976; Mc Kellar & Allen 1979; Rnby and Lucki 1980).”

“Industrially, the yellow discoloration is an important adverse effect of the ageing of polystyrene, e.g. during exposure outdoors (Geuskens et al. 1978a, 1978b; Weir 1978; Lucki and Rnby 1979; Rnby and Lucki 1980).”

“When polystyrene is subjected to UV irradiation in the presence of air, it undergoes a rapid yellowing and a gradual embrittlement Geuskens and David (1975). The mechanism of PS photolysis in the solid state (film) depends on the mobility of radicals in the polymer matrix and their bimolecular recombination.”

“The end group of PS or ketonic impurities also absorb the light of wave lengths longer than 300 nm (Geuskens and David 1979a, 1979b; Klopffer 1975; George and Hodgeman 1977).”

“Industrially, the yellow discoloration is an important adverse effect of the ageing of polystyrene, e.g. during exposure outdoors (Geuskens et al. 1978a, 1978b; Weir 1978; Lucki and Rnby 1979; Rnby and Lucki 1980).”

“Figure 41 Suggested process for photostabilization by benzothiazole complexes as peroxide decomposer, (Yousif et al. 2012).”

“Industrially, the yellow discoloration is an important adverse effect of the ageing of polystyrene, e.g. during exposure outdoors (Geuskens et al. 1978a, 1978b; Weir 1978; Lucki and Rnby 1979; Rnby and Lucki 1980).”

“2002), optical, electrical, magnetic and flammability properties of such a nanocomposite are much different from the polymer matrix itself Manzi-Nshuti et al. (2009).”

“Figure 31 The micro structure of carbon black particles, (Chirinos 1989).”

“Photooxidative degradation includes the following steps: (Rabek 1994; Rabek 1974; Guillet 1972a, 1972b).”

“Mayo (1978) because of efficient polymer alkyl radicals (P .”

“The end group of PS or ketonic impurities also absorb the light of wave lengths longer than 300 nm (Geuskens and David 1979a, 1979b; Klopffer 1975; George and Hodgeman 1977).”

“long period of time thus cause environmental pollution Singh and Sharma (2008). As waste plastic material has become a serious problem, recycling is receiving attention as a means of preserving the environment and reserving resources Pantano et al.”

“Many reviews have been published on photodegradation and photooxidation degradation of polystyrene (Pinto et al. 2013; Gijsman and Diepens 2009; Rabek 1995).”

“(ii) Quenching of the singlet oxygen ((1)O2) Allen et al. (1984). (iii) Decomposion of the hydroperoxides (OOH) radical, to non radical inactive species Yousif (2010). (iv) Scavenging of radicals (alkylperoxy (ROO) and alkyloxy (RO) Allen et al.”

“Alkoxy polymer radicals produced during the photolysis of hydroperoxide groups may decompose by β-scission reaction and to form a cetophenone and chain aliphatic ketone (Figure 23) (Kuzina and Mikhailov 1998; Geuskens et al. 1978a, 1978b).”

“Irradiation of polystyrene by UV. and visible light with wavelength (λ< 400) nm., leads to the formation of radicals whose nature is dependent on the spectral composition of the light and irradiation condition Kuzina and Mikhailov (1993).”

“It has the tendency to crystallize very quickly which gives it the favourable properties of high melting temperature and chemical resistance (Saitoh et al. 2003; Gupper and Kazarian 2005) (Figure 9).”

“…degradation of polymers, which include processes such as chain scission, crosslinking and secondary oxidative reactions, and takes place via radical processes , similar to thermal oxidation reactions (Ranby and Rabek 1981; Carlsson et al. 1976; Mc Kellar & Allen 1979; Rnby and Lucki 1980).”

“Yousif and Haddad SpringerPlus 2013, 2:398 Page 3 of 32 http://www.springerplus.com/content/2/1/398 Polymer degradation can be caused by heat (thermal degradation), light (photodegradation), ionizing radiation (radio degradation), mechanical action, or by fungi, bacteria , yeasts, algae, and their…”

“A number of impurities and irregularities in polystyrene, such as hydroperoxides, aromatic carbonyl groups, olefin bonds and chain peroxide linkages, can be responsible for the photoinitiation of the radical oxidation of polystyrene Rabek (1987). Irradiation of polystyrene by UV.”

“It has been shown that urethane and silylated derivatives of hydroxybenzophenones are effective photostabilizers, but cannot photostabilize polymers by intramolecular proton transfer Olson and Schroeter (1978). These compounds can act as: (Senna et al.”

“(Chandra 1983; Osawa et al. 1979).”