Photodegradation of polymers, relevance for coating chemist / Gurpreet Onkar Singh in PAINTINDIA, Vol. LX, N° 3 (03/2010)

[article]  inPAINTINDIA > Vol. LX, N° 3 (03/2010) . - p. 111-124 Titre : Photodegradation of polymers, relevance for coating chemist Type de document : texte imprimé Auteurs : Gurpreet Onkar Singh, Auteur ; V. C. Malshe, Auteur Année de publication : 2010 Article en page(s) : p. 111-124 Langues : Anglais (eng) Catégories : Matières plastiques -- Détérioration Oxydation Photodétérioration Polymères -- Détérioration Radicaux libres (chimie) Index. décimale : 667.9 Revêtements et enduits Résumé : The ageing of plastics, polymers and resins leads to several possibilities. Several oxidation products are formed. Free radicals, produced by formation of peroxides, lead to depolymerization, crosslinking, chain termination to polymer leading to chain branching and reversal to monomers in specific cases. Completely new small molecules those were not present at the time of polymerization are formed contributing to volatile organics over the useful life of the product and beyond it. When wa have a look at the literature on the subject of photodegradation of polymers, the polymer chemist dealing with bulk polymers seem to have worried about it far more than the paint and coatings chemist. The reasons are mainly environmental. The used plastic products are posing a great threat to the environment and efforts have been made to delibarately accelerate the process of photodegradation of polymers in ordinary sunlight. A paint and coating chemist can learn a lot from these developments, particularly "what not to do" to enhance the life of his products. Transition metals are regularly used to achieve various objectives by paint and coating chemist. There is a completely new dimension of their involvement in the degradation of polymers by photodegradation mechanism. This review is aimed at the spreading the information to the paints and coatings technologists. There is an increasing concern by government, NGOs and EU institutions about huge problems posed by letter and waste. Plastic products are significant contributors to these problems. The various additives, structural changes produced by oxidation assisted by light have been reviewed. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=9391 [article]

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Photodegradation of polymers, relevance for a coating chemist - Part II / Gurpreet Onkar Singh in PAINTINDIA, Vol. LX, N° 5 (05/2010)

[article]  inPAINTINDIA > Vol. LX, N° 5 (05/2010) . - p. 81-96 Titre : Photodegradation of polymers, relevance for a coating chemist - Part II Type de document : texte imprimé Auteurs : Gurpreet Onkar Singh, Auteur ; Vinod C. Malshe, Auteur Année de publication : 2010 Article en page(s) : p. 81-96 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Photodétérioration Polymères -- Détérioration Polystyrène Index. décimale : 667.9 Revêtements et enduits Note de contenu : - Influence of morphology - Combination of photo and biodegradation - Practical of photodegradable polymers - Fig. 13 : The variation of absorbance of carbonyl band with the exposure time for various - Fig. 14 : Change of yield stress v/s photodegradation time in UV chamber - Fig. 15 : Change of strain at break v/s photodegradation time in UV chamber - Fig. 16 : Photo induced weight loss of the polymer films under air or nitrogen atmosphere - Fig. 17 : FT-IR spectra of volatile products evolved from the irradiated PVC-TiO2 (1.5 wt. %) film under air. The inset shows the evolved CO2 concentration as a function of the irradiation time - Fig. 18 : Changes of average molecular weight polydispersity and gel amount in PS and PS with ketones after UV irradiation - Fig. 19 : Mechanism for photodegradation of PS - Fig. 20 : Mechanism for iniatiationof photodegradation of PS by benzophenone - Fig. 21 : Structure of WD-70 silicone - Fig. 22 : Weight loss curve of pure PS, PS-TiO2 and PS-GTiO2 composite films under illuination in air - Fig. 23 : Formation of active oxygen species - Fig. 24 : Dissociation of main chain of polystyrene containing carbonyl group - Table 3 : Stress-at-break of PS and PS with ketones (A=acetophenone, B=benzophenone) before and after UV irradiation - Table 4 : The variation of molecular weight of polymer films with irradiation time by GPC Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=34604 [article]

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