Media, paint

It s not as central a field as it used to be, but there is still an awful lot of interesting work going on. There are also many interested young people in the field though perhaps not as many as used to be in the past. Environmental chemistry is more popular these days. However, there is no contradiction between nuclear chemistry and environmental chemistry. Also, I don t think that people s fear of nuclear power plants is justified, but the media paint a bad picture and connect it with the waste disposal problem. 

Uses Surfactant, dispersant for titanium dioxide, other pigments in aq. media, paints, inks... 

Oil and gas service company wastes such as empty drums, drum rinsate, sandblast media, painting wastes, spent solvents, spilled chemicals, and waste acids... 

Use Manufacture of nylon solvent for cellulose ethers, fats, oils, waxes, bitumens, resins, crude rubber extracting essential oils chemicals (organic synthesis, recrystallizing medium) paint and varnish remover glass substitutes solid fuels fungicides analytical chemistry. 

Use Solvent, especially for vegetable oils low- temperature thermometers calibrations polymerization reaction medium paint diluent alcohol denatu-rant. 

Infrared spectroscopy is used in the paint industry for quality control, product improvement and failure analysis, and for forensic identification purposes [8, 18-21], Paints are mainly comprised of polymeric binders and pigments in a dispersive medium. The binders are commonly alkyds (oil-modified polyesters), acrylics and vinyl polymers. Titanium oxide is the most commonly used pigment, while water or organic solvents are used as the medium. Paints may also contain other additives such as fillers (e.g. calcium carbonate) and stabilizers (e.g. lead oxide). 

Perlite (rhyolitic obsidian) Aggregate in plasters, loose-fill insulation, filtration medium, paint filler, oil-well drilling muds, inert packing materials. 

Most of the trichloroethylene produced is used for metal degreasing. Other important uses are in the scouring of wool and as an extractive solvent, e.g. for olive and soya bean oils. Minor uses are as a heat transfer medium, anaesthetic, insecticide and fumigant, paint remover and fire extinguisher. 

The medium is the binder which provides for the adhesion of pigments. The most important types are the temper media (glue, egg, and gum), the oils, and wax. In addition, for wall painting there is the tme fresco technique, where the pigments are laid down in a fresh, wet plaster preparation layer. Several other media have been used, but much less frequendy, eg, casein temper. In modem paints, a number of synthetic resins are used for this purpose. Contemporary artist paints are often based on acryhc polymers (see Acrylic ester polymers Paints). 

The use of the various tempera and of wax has been identified on objects dating back to ancient Egypt. The Eayum mummy portraits are beautiful examples of encaustic painting, ie, using molten wax as medium. A rather special variation was the technique used by the Romans for wall paintings. In these, the medium, referred to by Pliny as Punic wax, probably consisted of partially saponified wax. In Europe, wax ceased to be used by the ninth century. 

The polysaccharides in gum arabic formed a medium used for illuminated manuscripts and inks (qv) as well as for painting. Gum is also the binder in watercolors. 

The proteinaceous gelatins in the various animal glues were also widely used as paint media, as well as in illuminations. Glues, the traditional media in Oriental painting, remained the prevalent binders for ground layers in European painting long after oils had become virtually the only medium for the color layers. 

The earhest written references to the use of oils as paint media date from the twelfth century. The van Eycks, who traditionally have been credited as the inventors of oil painting, improved the technique to such a degree that oil quickly replaced egg tempera as the prevalent medium. 

The most common problem in the paint layers, which can have a wide variety of causes, is loss of adhesion. Upon drying of the medium, the paint layers develop shrinkage cracks. In itself, this is not a particularly worrisome phenomenon, but, if through any cause the adhesion between paint layers and ground or between ground and support is lost, the paint begins to flake. First the flakes cud up, and finally become completely detached and lost. 

An important property of a pigment is its ability to maintain its color when exposed to light, weather, heat, and chemicals. This property is seldom measured for pigments alone. Rather it is determined for the dispersion of a pigment in a desired medium, eg, paints or plastics, and in many cases it is compared to the performance of a standard pigment. The observed changes are the result of complex pigment and media reactions and their possible interactions. In aH evaluations, time of exposure plays a role. 

Chlorinated rubberis often used in combination with medium od drying type alkyds. The alkyd gives better toughness, flexibdity, adhesion, and durabdity, and the chlorinated mbber contributes to faster drying and better resistance to water and chemicals. The principal appHcations are highway traffic paint, concrete floor, and swimming pool paints. 

Silicone resins with high phenyl contents may be used with medium or short oil alkyds as blends in air-dried or baked coatings to improve heat or weather resistance the alkyd component contributes to adhesion and flexibiUty. AppHcations include insulation varnishes, heat-resistant paints, and marine coatings. 

Beat-Cured Restm. For optimum comfort and to impede further loss of chewing efficiency, close adaptation of the denture base to contiguous oral tissues is required, which necessitates custom-made appHances. Nearly all dentures are made of acryHc resins. A wax pattern is used to form a custom denture base in which the denture teeth are embedded. A plaster or dental-stone investment spHt mold of this wax denture base and teeth is prepared. The wax portion is removed and the surface of the resulting mold cavity is painted with a separating medium, usually an aqueous solution of alginate, to aid in the removal of the cured acryHc from the plaster mold. 

There are, however, certain special applications where the filter medium around the edge of the section may be dehberately blinded by painting in order to improve cake discharge. This technique is most frequently used on disk filters, with the result that the actual area may be only 75 to 85 percent of the nominal area. This is a significant deviation from the nominal area and must be considered separately. 

Figure A13.1 A liquid painting system illustrating typical layout of a medium-size paint shop showing a seven-lank pre-treatment process...

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