Industrial plasters

The main physical and technological research work was done with an industrial plaster of pans. Synthetic hemihydrate prepared from dihydrate (MERCK 2161) and autoclaved a-hemihydrate were used for the examination of die retardation mechanism. 

Deductive mold materials are removed to form the desired shape. Inductive mold materials are built up to form the desired shape. Hardwoods, fiberboard, and industrial plaster are examples of deductive materials, which under certain circumstances can also be used inductively. Syntactic foam, thermoset plastics, papier mache, and sprayed white metals are normally considered to be inductive materials. 

Other uses - The hemihydrate form is used in a wide variety of construction and industrial plasters. Minor amoimts of purified gypsum are used in glassmaking and as a white filler (terra alba) in paint and paper. Soluble anhydrite , made by dehydrating gypsum into porous, highly absorbent granules, is used as a desiccant. 

Forming-Die Alloys. The tonnage of slab zinc used in this appHcation is small. The use of zinc alloy dies started in the aircraft industry during World War II (119). Zinc-based alloys cast in sand and plaster molds continue to be used for short-mn dies for steel and aluminum stampings in the automotive and aircraft industries (120). Considerable cost savings are realized with these low melting zinc-based alloys which are easy to poHsh, machine, weld, and remelt. 

P-Hemihydrate. The dehydration of gypsum, commonly referred to as calcination in the gypsum industry, is used to prepare hemihydrate, or anhydrite. Hemihydrate is generally called stucco in North America and plaster in many other continents. In North America, plaster is differentiated from hemihydrate or stucco by the inclusion of additives to control intended use properties, eg, rehydration time, density, coverage, strength, and viscosity. 

Demolition and construction wastes. Wastes from razed building and other structures are classified as demolition wastes. Wastes from the construction, remodeling, and repair of commercial and industrial buildings and other similar structures are classified as construction wastes. These wastes may include dirt, stones, concrete, bricks, plaster, lumber, shingles, and plumbing, heating, and electrical parts. 

Slip casting is common in the ceramics industry. The material to be cast is milled to a mean particle size of a few microns. A slip is made by mixing the finely divided material with a liquid suspending medium. The slip is then poured into a suitable mold (e.g., of plaster of pans). The liquid in the slip is drawn into the mold by capillary forces and the solids are deposited in a coherent form. For TiBj, ZrBj and CrBj a suspending medium of 5-7 wt% cyclopentadiene in xylene is recommended. A 3 wt% aqueous solution of carboxymethylcellulose is the best dispersing medium... 

Three other compounds of s-block elements—calcium oxide (CaO, known as lime ), sodium hydroxide (NaOH), and sodium carbonate (Na2 CO3)—are among the top 15 industrial chemicals in annual production. Lime is perennially in the top 10 because it is the key ingredient in construction materials such as concrete, cement, mortar, and plaster. Two other compounds, calcium chloride (CaCl2 ) and sodium sulfate (Na2 SO4 ), rank just below the top 50 in industrial importance. 

Used industrially as a fumigant, fungicide, animal repellent, insect attractant used in the preparation of medicinal ointments and mustard plasters used as a flavoring agent, and denaturant for alcohol. 

P.Y.108 is applied in various types of industrial finishes, especially in original automotive (O.E.M) and in automotive refinishes. It is also recommended for metallic finishes, although it is much less weatherfast in such systems. The pigment tends to seed, i.e., it forms specks upon storage. The mechanism behind this phenomenon remains to be elucidated. Besides, P.Y.108 also lends color to emulsion paints, in which it is durable enough to satisfy the requirements for exterior paints based on synthetic resin dispersions. It is also fast to acids, alkali, and plaster. 

Calcium carbonate occurs in nature as hmestone in various forms, such as marble, chalk, and coral. It is probably the most widely-used raw material in the chemical industry. It has numerous apphcations, primarily to produce cement, mortars, plasters, refractories, and glass as budding materials. It also is used to produce quicklime, hydrated lime and a number of calcium compounds. It is produced either as powdered or precipitated calcium carbonate. The latter consists of finer particles of greater purity and more uniform size. They also have many important commercial apphcations. Various grades of precipitated calcium carbonate are used in several products, such as textiles, papers, paints, plastics, adhesives, sealants, and cosmetics. 

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. 

Calcium oxide is one of the most important industrial chemicals. It is used in the manufacture of building and construction materials, including bricks, mortar, stucco and plaster. It also is used as a flux in the manufacture of steel. 

The use of porous formers in the dipping process, or porous molds prepared from plaster of Paris or unglazed porcelain with a surface pore size smaller than the majority of mbber particles, has been widely adopted in the latex industry. With the porous porcelain formers, the mbber particles are filtered on the surface of the formers. The mbber latex coagulates because of its high concentration to form a film of increasing thickness as more water is absorbed into the ceramic. Its rate of increase diminishes sharply beyond an optimum period of time, however, depending on the various characteristics of the ceramic. 

It is interesting with reference to the above statements of Dioscorides, to note in S. P. Sadtler s Industrial Organic Chemistry, written 1800 years afterward, the statement that the practice of plastering undoubtedly has an injurious effect upon the consumers of wine. ... 

Calcined Anhydrite. Soluble anhydrite, or second-setde stucco, has physical properties similar to those of gypsum plaster. It hydrates to the dihydrate rapidly in water. Its outstanding property is its extreme affinity for any moisture, which makes it a very efficient drying agent (see Desiccants). In ambient moisture-laden air, it readily hydrates to hemihydrate. Soluble anhydrite, under the trade name Drierite, is widely used as a desiccant in the laboratory and in industry. A small amount is also used as an insecticide carrier. Small amounts of soluble anhydrite are unintentionally produced in most commercial calciners during hemihydrate production. 

Because of the radiation resistance of polyurethanes, they find use in the nuclear industry. Polyurethanes find an important use in short-run production where parts can be made accurately until more costly molds can be made, without the need for potentially expensive change. Polyurethanes can be used to make molds for casting polyurethane parts. A coat of mold release is required for easy part removal. These molds can be used for short-to-medium production runs. Polyurethane molds can be made from a variety of different materials. Only very low-density wood and high-moisture-containing materials such as plaster of Paris prove to be too difficult to prepare a mold. 

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