Transparent foams

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Uses Acrylic producing stable transparent foam coatings Features Rubber touch effect Properties Wh. si. vise, paste Tubicoat STC 100 [CHT R. Beltllch GmbH]... 

Uses Compd. producing stable foam coatings according to the transparent foam process... 

Uses Acrylic producing stable transparent foam coatings, table cloth coating... 

Different regions of the world have developed different practices over the years. North America relies almost exclusively on tin compounds for transparent foam sheet, pipes and fittings and window frames, whereas most of the rest of the world has continued to favour lead. Within Emope, there are differences between individual countries. The UK and Finland appear to favour calcium-zinc mixed metal stabilisers when not using lead, whereas calcium-organic combinations are popular in the Netherlands and Norway. France and Belgium, like the US, use tin for water pipe. The global position in 2002 (shortly after the trend away from lead in Europe became industry policy) is summarised in Chapter 6. 

Pure amorphous polymers, being homogeneous materials, are transparent. Atactic polystyrene is a good example. The crystalline syndiotactic form is not transparent. Alack of transparency does not necessarily indicate crystallinity, however. It can also be caused by inorganic fillers, pigments, gas bubbles (as in a foam), a second polymer phase, etc. 

For use in soap bars, a smooth feel after washing, mildness, lime soap dispersing effect, and foaming properties are important [36,104-106]. In transparent soap bars the clarity will be improved [104], in half-syndet soaps mildness and foam are increasing [105,106] combined with a smooth feel after use [105], With lauryldiglycolamidether carboxylate a good foaming and mild syndet soap has been formulated [36]. 

Secondly, a stable icing foam requires a low surface tension. Consider the case of egg whites in a beater. With slight whipping, entrapped air bubbles are large and the whites appear foamy, yet transparent and runny. With longer whipping the whites become less transparent, white, and more solid. Thus, because of the low surface tension inherent in the egg protein in solution, more and more air may be incorporated and held in place by the colloidal protein which forms a film around each air cell. 

Polystyrene (PS), a highly rigid and surface-hardened thermoplastic, is glass clear and almost colorless. Its typical slight yellow tinge is easy to compensate for by adding transparent blue colorants to adjust the color. Polystyrene softens between 80 and 100°C. It is processed between about 170 and 280°C, up to a maximum of 300°C, without color change, by any of the methods which are recommended for thermoplastics. The list of products includes extrusion made sheets, profiles, and films, which are often foamed. 

Injected parts transparent, filled to a greater or lesser degree, possibly crosslinked and/or foamed in microcellular form for tyres (light uses), kneepads, footwear, soles, sports and technical items, buoys, flexible toys, protective caps. .. 

The opacity of plastic foams, and polymers with scratched surfaces, is also governed by Fresnel s law. The n value of the gas which occupies the scratch indentation is much lower than that of the polymer. Light may be directed through rods of transparent polymers, such as PMMA. This effect may be enhanced when the rod or filament is coated with a polymer with a different refractive index, such as polytetrafluoroethylene (ptfe). Optical fibers utilize this principle. 

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