Applications plasters

The use of monomer-polymer doughs has been largely confined to the production of dentures. A plaster of Paris mould is first prepared from a supplied impression of the mouth. Polymer powder containing a suitable polymerisation initiator is then mixed with some monomer to form a dough. A portion of the dough is then placed in the mould, which is closed, clamped and heated in boiling water. After polymerisation, which usually takes less than half an hour, the mould is cooled and opened. This technique could also be usefully employed for other applications where only a few numbers-off are required but does not seem to have been exploited. 

Magnesium oxychloride cements are widely used for the fabrication of floors. They find application for this purpose because of their attractive appearance, which resembles marble, and also because of their acoustic and elastic properties and their resistance to the accumulation of static charge. They have also been used for plastering walls, both interior and exterior for exterior walls the cement often includes embedded stone aggregate (Sorrell Armstrong, 1976). However, there have been problems with this latter application, since the base cement has been found to be dimensionally unstable and, in certain circumstances, to release corrosive solutions and show poor weather resistance. 

P.V.23 is a favorite shading pigment for use in emulsion paints, where it lends a reddish tinge to Phthalocyanine Blue shades. Excellent weatherfastness makes it a suitable candidate for exterior application in media based on synthetic resin dispersions. The systems are fast to alkali and plaster. 

Several different materials and installation systems are available and include various types of proprietary materials, plasters containing perlite or ver-miculite, concrete mixtures, or lightweight concretes. The selected material and installation system, encasement, or surface application should provide protection for the expected fire duration. For more information refer to Chapter 7, Section 7.3.2. 

At this point, Lavoisier was primarily interested in doing research that would impress the academicians. He read his first paper to the Academy as a visiting scientist (that is, a non-member) on February 27,1765. It dealt with a topic that had been pursued by some of the chemists in the Academy and was titled The Analysis of Gypsum. Gypsum was the mineral from which plaster was made, so it was a topic with practical applications. The two referees appointed by the Academy to judge the paper reported favorably on it and recommended it for inclusion in the Academy s Savants etrangers collection. It is probable that some sort of behind-the-scenes deal had been made because both referees were friends of Lavoisier s father. 

Calcium hydroxide has wide industrial applications. It is used to make cement, mortar, plaster, and other building materials. It also is used in water soluble paints, and for fireproofing coatings and lubricants. Other applications are in the manufacture of paper pulp as a preservative for egg in vulcanization of rubber as a depilatory for hides and in preparation of many calcium salts. 

Plasters made from hemiliydrate also find applications in many orthopedic and dental materials and sanitary wares. 

In another application expanded polystyrene foam panels, 1.2 x 2.4 m, are faced with a wire mesh and mounted in a metal channel bolted to a concrete slab. These panels are then sprayed on both sides with plaster, which is anchored to the wire mesh and forms the interior and exterior surfaces. Roof and interior partitions provide low cost housing for mild climates. 

The hemihydrate (stucco) is normally produced by heat conversion of the dihydrate from which 3/2 H20 is removed as vapor. The resulting powder is also Ten own as plaster of Paris [26499-65-0]. Stucco has the greatest commercial significance of these materials. It is the primary constituent used to fabricate products and in formulated plasters used in job- or shop-site applications. 

If soluble anhydrite is desired, firing is maintained until a second boil occurs accompanied by a second temperature plateau at about 190°C. Virtually all the water of crystallization has been removed at 215°C. Soluble salts are impurities that increase the vapor pressure within the kettle. Aridized stucco refers to ketde-calcined hemihydrate that has been made with the intentional addition of 0.55—1.1 kilograms of NaCl or CaCl per metric ton of land plaster. The stucco characteristic of lower water demand permits higher density and higher strength casts. The hygroscopic nature of the chlorides prevents the use of aridized stucco for some applications. 

Although metals and alloy substrates account for much of the volume in electroplating, there is a large and growing amount of plastic surfaces being plated, both for decorative trim and for electronic shielding applications. On a smaller scale, other materials that are plated include wood (qv), plaster, fibers (qv) and cloth materials, and plant and animal tissue, such as leaves, leather (qv), paper (qv), and seashells. 

With the exception of local application of ethylmorphine to the conjunctiva or the tympanum to produce hyperemia, there are no rational local uses of opium alkaloids. These drugs are not local anesthetics and relieve pain only by central actions. Indeed, irritation and vesication may result from opium plasters, ointment, or washes applied to the skin or mucosa. 

Because of its analgesic (painkilling) properties, opium and its derivatives have long been used for the treatment of ailments. Throughout the nineteenth century in England and the United States, opium was administered in plasters, pills, cough drops, lozenges, and many other applications dispensed by physicians and pharmacists. 

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