Weathering, of polymers

All of the factors involved in weathering, including both the amount of intensity of sunlight, vary both seasonally and geographically. To understand fully and predict the weathering behaviour of any polymer requires information about exactly how these factors vary and how they then contribute to the overall degradation process. 

Hence either the reactive singlet oxygen molecule or oxygen atoms are produced either of these may initiate radical chain processes that lead to degradation. 

Alternatively because of the degree to which it both reflects white light and absorbs in the ultraviolet, it may inhibit photodegradation. Which of these two possibilities predominates depends on a variety of factors including the concentration of the TiOj pigment used, the nature of any surface treatments, and the extent to which the polymer itself is able to resist photodegradation. 

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Report 53 Weathering of Polymers, S.M. Halliwell, Building Research Establishment. 

A. Davis and D. Sims, Weathering of Polymers, Applied Science, London, 1983. 

Davis A and Sims D, "Weathering of Polymers", Applied Scientific Publishers (Elsevier), London, 1983. 

FIGURE 5.3 Accelerated and real-time weathering of polymer materials obtained at NREL. PET, polyethyleneteraphthalate PVDF, polyvinylidenedifluoride PE, polyethylene PC, polycarbonate PMMA, polymethylmethacrylate. 

Davis A, Sims D (1983) Weathering of Polymers, Appli Sci Publishers New York, p242... 

The effect of excessive heat results in the degradation of the eqviip-ment by corrosion and weathering of polymer and plastic materials used in the plant. The corrosion reactions are very rapid at elevated temperatures. 

Davis, A. Sims, D. Weathering of Polymers Applied Science London, 1983. 

Photochemically induced H-abstraction includes the electronically excited nitrox-ide pNO ] and occurs even at room temperature. The activation energy was reported to be 21 kJ/mol. The quantum yield is ca. 0.2 with light of wavelength <360 nm. Because of the air present during weathering of polymers, it is likely that the excited nitroxide is efficiently quenched by oxygen [189] and the photochemical formation of NOH is only negligible (Eq. 32, pathway a) ... 

In the photoageing of polycarbonates, photo-oxidation has been shown to be a more important process than the photo-Fries reaction. The photo-oxidation of epoxy-resins has been found to depend on the type of hardener and its concentration. A correlation has been observed between the changes in chemical structure and thermally stimulated current of poly(vinyl alcohol) during photo-oxidation. Other studies of interest include the weathering of polymers outdoors,effect of ozonation on polymers, effect of drawing, effect of biodegradation, and changes in mechanical properties of thermoplastics. ... 

Solar radiation plays an important role in weathering of polymers. This fact even more complicates the transformation of antioxidants. Because ROO-CHD s contain both a peroxidic bond and a carbonyl group in one molecule, they take part in the... 

According to142), also the catalytic cleavage of ROO-CHD and formation of RO radicals in this way have to be concerned among the processes which play a role in the weathering of polymers. 

With respect to the presence of carbonyl group and the system of conjugated double bonds, participation of quinoid compounds in light-induced reactions, and, consequently, their active role in weathering of polymers have to be considered. Great attention was paid to the light-induced reactions of quinones generally223 ... 

The photooxidation and weathering of polymers is a subject of Immense commercial concern, and occupies the attentions of large numbers of research workers. The literature on the subject in vast, and a review of the field cannot be attempted within the scope of the present chapter. Readers are directed to other authoritative reviews (103-109). Instead here we confine attention strictly to aspects of the subject in which luminescence studies might be of relevance. 

Research on the durability, thermal resistance, frost resistance and weatherability of polymer-modified mortar and concrete [24-27]... 

Y. Ohama, T. Moriwaki and K. Shiroishida Weatherability of polymer-modified mortars through ten-year outdoor exposure, in Proceedings of the 4th International Congress on Polymers in Concrete, Institut fur Spanende Technologie und Werkzeugmaschinen, Technische Hochschule Darmstadt, Darmstadt, West Germany (1984), pp.67-71. 

A Davis and D Sims, Weathering of Polymers, Barking, UK, Apphed Science 1983. 

D Roylance and P McElroy, Weathering of polymer composites . Composites Asia Pacific 89 Conference Proceedings Adelaide, 19-21st June 1989, pp 29-39. 

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