Photostabilization

The photostabilization of polymers continues to be a highly prolific area of industrial and academic interest, particularly as new systems are constantly being developed. Several review articles have appeared discussing the types of conventional light stabilizers available and their possible modes of action. Other articles have dealt with the physical aspects of syner- 

Bortolus, Proc. lUPAC, Macromol. Symp., 28lh, 1982, 279. 

Dexter, in Kirk-Othmer Encycl. Chem. Technol., 3rd Ed. , ed. M. Grayson and D. Eckroth, Wiley Interscience, New York, 1983, Vol. 23, p. 615. 

Carlsson and D. M. Wiles, Proc. TUPAC, MacronK l. Symp., 28th, 1982, 325. 

The photostabilization of polymers continues to be a rapidly advancing area of scientific and technological interest. Carlsson and Wileshave written several reviews on photostabilizing mechanisms in polymers, while Swasey has given an updated guide to stabilization, and Reid has discussed the effects of stabilizers in vinyl polymers. Nemzek and Mayo have predicted the service life of polypropylene, and Bredereck has reviewed the photostabilization of PVC. Several comprehensive review articles have appeared. Pospisil has reviewed in considerable depth the photo-oxidation mechanisms of phenolic anti-oxidants, Shlyapintokh has reviewed the kinetics of stabilizer distribution, Vink has 

Joffe and B. Ranby, J. Appl. Polym. Sci., Appl. Polym. Symp., 1979, 35, 307. 

Borodulina, M. S, Kurzhenkova, T. E. Pashchenko, T. N. Zelenkova, and T. M. Yanishihikova, Plenoch Polim. Mater. Ikh Primen. Mater. Kratkosrochnogo Semin, 1977, 43. 

Pospisil, in Developments in Polymer Photochemistry , ed. N. S. Allen, Applied Science Publishers Ltd., London, 1981, Vol. 2, Chap. 3, p. 53. 

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Copper-based thermal stabilizers are also effective photostabilizers for nylon. They can be added before polymerization, or the soluble salts (eg, CuSO can be appHed to fibers as part of the finish or to fabrics as post-treatments. The effectiveness of the copper salt—alkah haUde system added to prepolymer in retarding phototendering and photoyeUowing of the resulting spun yam is illustrated in Figure 5. 

H-l,2,3-Benzotriazole, 2-phenyl-oxidation, 5, 721 as photostabilizers, 5, 731 synthesis, 5, 722 Benzotriazoles acylation, 5, 54 antifogging agents... 

Additives such as antioxidants and photostabilizers of low-molecular weight face two major problems (1) they may evaporate during high temperature moulding and extrusion process or (2) they may migrate to the surface of the plastic and get extracted. There are, in general, three ways of overcoming these problems. 

The photostabilizing efficiency of polymer-bound HALS in i-PP and E-P copolymers were studied and compared with commercial HALS (i.e., Tinuvin 770 and Chimassorb 944) by measuring the carbonyl index at 1720 cm. Plots of carbonyl index versus irradiation... 

J. F. Rabek and B. Ranby, Photodegradation, Photo-oxidation and Photostabilization of Polymers, Interscience, New York (1975). 

Photodegradation of polyethylene waste can be markedly accelerated via its grafting with acrylamide [98], In contrast, photostabilization of polyethylene and polypropylene can be achieved as a result of the grafting of 2-hydroxy-4-(3-methacryloxy-2-hydroxy-propoxy) benzophenone using gamma radiation [ 147], In this case, the grafted compound acting as a U V stabilizer is chemically bound to the backbone chain of the polymer and its evaporation from the surface can be avoided. 

When the photostabilization of a polymer material is to be obtained through such a surface treatment process, it is all important to make sure that the protective effect will last throughout the service life and therefore to ensure a long-term adhesion of the coating onto the substrate. This can be best achieved by promoting a grafting reaction between the two elements (20). For that purpose, the photoinitiator was partly incorporated in the top layer of the PVC plate by a surface treatment with an acetone solution. Upon UV-irradiation of the resin-coated sample, the following reactions are expected to occur ... 

Ultraviolet radiation, effect on commercial polymers, 201 Ultraviolet-cured coatings hydroxy-benzotriazolc, 213 photostabilization of PVC, 213 Ultraviolet-visible spectrum,... 

In Photodegradation and Photostabilization of Coatings Pappas, S., et al. ACS Symposium Series American Chemical Society Washington, DC, 1981. 

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