Phosphoric acid magnesium phosphate cements

The reaction of phosphoric acid (usually in the form of ammonium phosphate) with magnesium oxide in the presence of water gives magnesium phosphate cements. These are used for rapid repairs, for example of pot holes in busy roads. 

The process of fabrication of zinc phosphate cements is very similar to that of magnesium phosphate ceramics. Direct reaction with phosphoric acid is fierce and needs to be slowed down. This is done by the following methods. 

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. ... 

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