Properties and Application of Glass

Glass: - It is an amorphous substance. It consists of silicates and in some cases borates and phosphates. Glass is an inorganic material made by the fusion of different metallic oxides. The properties of glass are -

i)   It is transparent, brittle and hard

ii)   Glass is insoluble in water and usual organic solvents

iii)   It has low dielectric loss, slow ageing and good mechanical strength

iv)   It is susceptible to destruction when sudden and high temperature cycles are applied

Uses - Glass is used in moulded insulating devices such as electrical bushings, fuse bodies, insulators. Glass is used as a dielectric in capacitors. Radio and television tubes, electrical laminated boards also make use of glass

Glass Products

a)   Silica glass or fused quartz - Silica when heated to a temperature of fusion and then cooled is known as silica glass. This material has good electrical properties, low coefficient of expansion and high resistivity.

b)   Borosilicate glass or Pyrex - This glass requires 28 per cent of boron oxide along with other oxides. They resist the effect of chemicals and moisture better than other glasses.

c)    Fibre glass insulation - This is capable of withstanding high temperature. For most applications fibre glass is impregnated with materials like synthetic resins or with mineral oil. They possess good electrical and mechanical properties and sufficient flexibility to be moulded into required shapes.

d)  Epoxy glass - It is made by joining glass fibre layer with a thermosetting compound. It is immune to alkalies and acids and is used in PCB making, terminal holders and instrument cases.

Properties

1)      It has high resistivity & dielectric strength at ambient temperature.

2)      Temperature coefficient is -ve and very large.

3)      Tensile strength is low.

4)      Coefficient of thermal expansion considerably varies with composition.

5)      It is susceptible to destruction when used in high and low temperature cycle.

6)      Surface resistivity falls considerably when exposed to moisture.

Applications:- Moulded glass is used in electrical bushings, fuse bodies, insulators. It is used as dielectric in capacitors. It is used in the manufacture of radio and television tubes,electrical lamps, and laminated boards. It is used to make optical fibers used in optical communications.