Discuss important properties and uses of Mica and Mica Products.
Mica and Mica Products - Mica is an inorganic material. This is one of the best insulating materials available. By the electrical viewpoint, mica is of two kinds - Muscovite mica and Phologopite mica.
Muscovite mica - Chemical composition is KH2Al3(SiO4)3.
Properties:
i) Strong, less flexible and tough
ii) Colourless, silver, yellow or green in colour
iii) Insulating properties are extremely good
iv) Abrasion resistance is high
v) Alkalies do not influence this
Uses - Muscovite mica is used here electrical requirements are severe. Due to high dielectric strength, this is used in capacitors. This is also used in commutators because of high abrasion resistance.
Phologopite mica - Chemical composition is KH(MgF)8MgAl(SiO4)3.
Properties
i) Amber, green, yellow or grey in colour
ii) Being tougher and harder than muscovite mica, greater structural stability and less rigid
iii) Resistant to alkalies, must be less to acids
iv) Greater thermal stability than which of muscovite mica
Uses - This is used when there is greater require of thermal stability like in domestic appliances as irons, hotplates and toasters.
Mica products
(i) Glass bonded mica - Ground mica flakes and powdered glass while moulded makes glass bonded mica. Such material is impervious to water and chemically stable. It is used in high humidity and high ambient temperatures.
(ii) Mica paper and Mica sheet- Mica is broken in small particles into aqueous solution. Out of such sheets of mica paper are produced that are used as insulation for armature and field coils of rotating machines. As well used for washers, sleeves, spacers and tubes.
(iii) Manufactured mica - Mica flakes held together along with adhesives is termed as manufactured mica. This is used in commutators, motor slot insulation, electrical heating devices and transformers.