The mica , whose name derives from Latin micare (to shine), is a Minéral made mainly of Silicate of Aluminum and Potassium. With the quartz and the Feldspar, it is one of the components of the granite.

Types of mica

It is characterized by its laminated structure (family of the Phyllosilicate S), its metallic luster and its great heat strength. The properties of the micas, them Transparency, their homogeneity, their properties of thermal Insulator, make that one finds them in many uses.

The micas are classified in two series:

  • the white micas dioctaedric XY3+27- are silicates rich in aluminum and potassium.
the white mica most frequent is the Muscovite K+Al3+27-.
  • the black micas trioctaedric XY2+37- are silicates containing especially Magnésium with potassium and brown Fer
Of color to black, the black micas belong to the main components of the Granite S, of the Gneiss and of the Micaschiste S. Them Altération transforms them into Chlorite S.
the black mica most frequent is the Biotite K+ (Mg, Fe, Ti) 2+37-.

The two types of mica are in the eruptive rocks and metamorphic. They are detrital when one finds them in the sedimentary rocks.

Uses of the mica

Use in the form of paper mica

The mica is used for its properties of electrical insulator and heat strength.

Industrially, the mica is put in pulp in water, then transformed into paper mica (using machines identical to the traditional paper machines). The rolls of paper mica are then unrolled, impregnated uninterrupted resins (organic or Silicones), and if necessary pasted on a support which can be a glass fiber fabric or a polymer sheet, then rewound.

These rolls of paper impregnated and pasted are then:

- is cut out in sheets, several sheets then being able to be piled up and in a hurry to give plates various thicknesses, more or less flexible;
- is cut out in the direction length to produce ribbons.

The principal applications are the following ones:

- ribbons for insulation of the copper bars in the engines and alternators with High voltage;
- ribbons for fire-resistant protection of the electric cables in the installations where the safety requirements are important (tunnels, boats, airports, hospital, subway, etc); protection mica indeed makes it possible the installations to longer function in the event of Incendie;
- plates of heating for industrial applications or equipment electric household appliances (toaster, hair drier, microwawe oven, etc);
- various industrial applications (induction furnaces, joints, insulating parts), joined automobile.

The mica replaced the Amiante in a certain number of applications at high temperature or protection against the Incendie, because it does not present similar risks at all (material inert, nontoxic, being presented in the form of spangles and not fibers).

Use in the form of spangles or of powder

The mica is used for its properties of fire resistance, its chemical inertia, its covering capacity, its capacity of soundproofing.

In this form it is used like charges in paintings, coatings, plastics.

It is also incorporated in other materials like acoustic insulator (motor vehicles) or fire-resistant (doors firebreak).

One also uses it for his esthetic and decorative aspect (cosmetics).

See too

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