Copper phosphate cements

There is virtually no knowledge of the setting and stmcture of copper phosphate cements. Mostly, they are complex materials. The simplest was based on a powder containing 91-5% CuO and 8-4% CO3O4. Others contained respectively 62-2 % CuO and 29-8 % ZnO, and 23-9 % Cu O and 66 7% ZnO, with other metal oxides. The strength of these cements is about the same as the zinc phosphate cement (Ware, 1971). There are also pseudo-copper cements, which are zinc phosphate cements coloured by minor amounts of copper(II) oxide. 

More recently copper phosphate cements have been suggested for use as controlled-release agents for supplying trace amounts of copper to cattle and sheep over an extended period (Allen et al., 1984 Mansion et al., 1985 Prosser et al., 1986). The cements were prepared with a Cu/P ratio of 1 1 to ensure that the matrix was an add phosphate and so subject to dissolution in aqueous solutions. They released copper at a constant rate for 90 days. 

Vashkevich, N. K. Sychev, M. M. (1982). Setting of copper phosphate cements in the presence of organic polymers. Chemical Abstracts, 97,... 

Zinc phosphate, Zn2(P0 2> forms the basis of a group of dental cements. Chromium and zinc phosphates are utilized in some metal-treating appHcations to provide corrosion protection and improved paint adhesion. Cobalt(II) phosphate octahydrate [10294-50-5] Co2(P0 2 8H20, is a lavender-colored substance used as a pigment in certain paints and ceramics. Copper phosphates exhibit bioactivity and are used as insecticides and fungicides. Zinc, lead, and silver phosphates are utilized in the production of specialty glasses. The phosphate salts of heavy metals such as Pb, Cr, and Cu, are extremely water insoluble. 

A current area of interest is the use of AB cements as devices for the controlled release of biologically active species (Allen et al, 1984). AB cements can be formulated to be degradable and to release bioactive elements when placed in appropriate environments. These elements can be incorporated into the cement matrix as either the cation or the anion cement former. Special copper/cobalt phosphates/selenates have been prepared which, when placed as boluses in the rumens of cattle and sheep, have the ability to decompose and release the essential trace elements copper, cobalt and selenium in a sustained fashion over many months (Chapter 6). Although practical examples are confined to phosphate cements, others are known which are based on a variety of anions polyacrylate (Chapter 5), oxychlorides and oxysulphates (Chapter 7) and a variety of organic chelating anions (Chapter 9). The number of cements available for this purpose is very great. 

The most important of the phosphate bonded cements are the zinc phosphate, dental silicate and magnesium ammonium phosphate cements. The first two are used in dentistry and the last as a building material. Copper(II) oxide forms a good cement, but it is of minor practical value. In addition, certain phosphate cements have been suggested for use as controlled release agents. The various phosphate cements are described in more detail in the remainder of this chapter. 

The setting rates of these dental cements are controlled by prior sintering of the oxide powder and by the addition of buffering aluminium salts to the phosphoric acid. Small quantities of MgO, Si02, AI2O3, and so on are usually included in the formulation. Anti-bacterial action can be achieved by the addition of some CuO which produces small quantities of non-white copper phosphates. 

These cements are based on the reaction product of phosphoric acid with other materials, such as sodium silicate, metal oxides and hydroxides, and the salts of the basic elements. Zinc phosphate is the most important phosphate cement and is widely used as permanent dental cement. It is also modified with silicones to produce dental-filling materials. Compressive strengths of up to 200 MPa are typical of these materials, which are formulated to have good resistance to water. Copper phosphates are used for similar applications, but they have a shorter useful life and are used primarily for their antiseptic qualities. Magnesium, aluminum, chromium, and zirconium phosphates are also used. ... 

The method involving the Mo-V-P acid has been used in determinations of phosphorus in biological tissues [127], plant material [128], fruits [129], fish products [130], foodstuffs [131], phosphate minerals [132], cast iron and steel [133,134], niobium, zirconium and its alloys, titanium and tungsten, aluminium, copper, and white metal [135], nickel alloys [134,135], metallurgy products [136], molybdenum concentrates [137], silicon tetrachloride [7], cement [138], and lubricants[139]. The flow injection technique has been applied for determining phosphate in minerals [140] and in plant materials [141]. 

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