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Author: D. M. J. Compton
Publisher:
ISBN:
Category :
Languages : en
Pages : 99
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Book Description
Progress of an investigation on the mechanisms of degradation of white pigments used in polymeric thermal control coatings by ultraviolet radiation is reported. The materials investigated were rutile (TiO2) with different controlled impurity levels and surface treatments and high-purity strontium titanate (SrTiO3). Apparatus combining a gas chromatograph with means for measuring optical reflectance and electrical conductivity enables samples of pigments to be investigated in a controlled environment. Changes in optical properties, produced by exposure to ultraviolet light, are correlated with gas evolution and adsorption. Some optical changes were correlated with gas evolution and electrical conductivity. The gas evolved in all cases was CO2, with no O2 being observed. Carbonaceous impurities found in these materials are believed to play a role in the damage process. Instrumentation and test techniques were developed, including a recently completed reflectometer of novel design. A comparison was made between chemical reduction of various rutile pigments and the effects of uv light: Chemical reduction produces changes in optical and other properties that correlate with one of the two types of effects produced by uv light (reduction of reflectance near one micron) and the relative susceptibility of different pigments to chemical reductions similar to their relative susceptibility to uv degradation.
Author: D. M. J. Compton
Publisher:
ISBN:
Category :
Languages : en
Pages : 99
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Book Description
Progress of an investigation on the mechanisms of degradation of white pigments used in polymeric thermal control coatings by ultraviolet radiation is reported. The materials investigated were rutile (TiO2) with different controlled impurity levels and surface treatments and high-purity strontium titanate (SrTiO3). Apparatus combining a gas chromatograph with means for measuring optical reflectance and electrical conductivity enables samples of pigments to be investigated in a controlled environment. Changes in optical properties, produced by exposure to ultraviolet light, are correlated with gas evolution and adsorption. Some optical changes were correlated with gas evolution and electrical conductivity. The gas evolved in all cases was CO2, with no O2 being observed. Carbonaceous impurities found in these materials are believed to play a role in the damage process. Instrumentation and test techniques were developed, including a recently completed reflectometer of novel design. A comparison was made between chemical reduction of various rutile pigments and the effects of uv light: Chemical reduction produces changes in optical and other properties that correlate with one of the two types of effects produced by uv light (reduction of reflectance near one micron) and the relative susceptibility of different pigments to chemical reductions similar to their relative susceptibility to uv degradation.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 113
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Book Description
An investigation has been conducted on the mechanisms of degradation of pigments and polymeric coatings for thermal control applications exposed to ultraviolet (uv) and electron irradiation. The materials investigated were rutile (titanium dioxide) and strontium titanate (SrTiO3). The effects of treating the pigments by heating in various gas ambients at elevated temperatures were studied using gas chromatography and electrical conductivity measurements. Significant changes in the surface characteristics were found to result from these treatments. A comparison was made between the reflective degradation in binderless pigments and silicone-binder coatings exposed to uv light, to energetic electrons, and simultaneously to uv light and electrons. Evidence for stabilization of defect sites by charge capture was discovered in the binderless pigment experiments. This mechanism for defect stabilization does not appear as prevalent in the silicone-binder coatings, since the binder apparently passivates the pigment surface to some extent. The fluence dependence of the degradation and the recovery of the damage in vacuum and in the presence of various gas ambients was also studied.
Author: Krzysztof Pielichowski
Publisher: iSmithers Rapra Publishing
ISBN: 9781859574980
Category : Science
Languages : en
Pages : 324
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Book Description
Understanding the thermal degradation of polymers is of paramount importance for developing a rational technology of polymer processing and higher-temperature applications. Controlling degradation requires understanding of many different phenomena, including chemical mechanisms, the influence of polymer morphology, the complexities of oxidation chemistry, and the effects of stabilisers, fillers and other additives. This book offers a wealth of information for polymer researchers and processors requiring an understanding of the implications of thermal degradation on material and product performance.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704
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Author: William B. Campbell
Publisher:
ISBN:
Category :
Languages : en
Pages : 70
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Two different types of polydimethylsiloxane formuated with a rutile titanium dioxide pigment were evaluated as polymeric thermal control coatings. Oxygen permeability, diffusion, and solubility in these coatings were measured for various temperatures. It was noted that diffusion and permeability coefficients decreased as pigment concentration increased. Morphological investigations comparing surface roughness and surface area to the ultraviolet stability of a zinc orthotitanite coating indicated that pigment surface area is directly related to the increase in solar absorptance. (Author).
Author:
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Category : Military research
Languages : en
Pages : 854
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Author: United States. National Aeronautics and Space Administration
Publisher:
ISBN:
Category :
Languages : en
Pages : 792
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Author:
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ISBN:
Category : Astronautics
Languages : en
Pages : 794
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Author: N. Grassie
Publisher: Springer Science & Business Media
ISBN: 9400934254
Category : Science
Languages : en
Pages : 282
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Book Description
The purpose of this volume, like that of its predecessors in the series, is to present a selection of topics which are representative of the continually expanding area of polymer degradation. It will be obvious that some of these topics emanate from academic studies, others from more applied backgrounds, but it is anticipated that all will be seen to be of vital relevance to one or other of the currently advancing fields of polymer technology. The first two chapters deal with specific classes of polymers, and particularly with their mechanisms and products of thermal degrada tion. Thus in Chapter 1 Dr McNeill discusses the reactions of the ammonium, alkali and alkaline earth metal salts of poly(methacrylic acid) and their copolymers with methyl methacrylate. These water soluble 'ionomers' have valuable technological applications. In Chap ter 2 Professor Montaudo and Dr Puglisi perform a valuable service by drawing together and critically reviewing, for the first time to my knowledge, the mechanisms of thermal degradation of the various classes of condensation polymers which are of industrial significance. This includes, for example, the polyurethanes, polyureas, polyesters, polycarbonates, polyamides, polyimides, polyethers, polysulphides, polysulphones, polyschiff bases, polysiloxanes and polyphosphazenes.
Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 1054
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