Man Made Materials

Plastics

Glass is a homogeneous mixture containing sodium and calcium silicate. It is non-corrosive and widely used in various fields. It  is also known as super cooled liquid or pseudo solid due to its ability to flow.

Manufacture of glass:

• Raw materials: Scrap glass, sand, limestone and sodium carbonate are the raw materials used for the manufacture of glass.

• Process: Raw materials in the finely powdered form are introduced into furnace at a temperature of about 1700-1800°C, where sodium and calcium carbonate reacts with silica to form sodium and calcium silicate respectively.

Na₂CO₃ + SiO₂ → Na₂SiO₃ + CO₂

CaCO₃ + SiO₂ → CaSiO₃ + CO₂

The molten glass thus obtained is cast into the mould or drawn into various shapes. It is slowly cooled to provide  tensile strength; this slow cooling process of glass is known as annealing. It is done, because on sudden cooling glass may be crack or  bubbles amy appear on the surface of the glass..

Note: To remove air bubbles in the glass during its manufacturing, borax or aluminium powder is added to the glass and heated slowly.

Properties of glass and its uses:

Glass is strong, corrosion free and a transparent material which is used in various fields. It usually softens on heating and begins to flow. One of the properties of glass which acts as its demerit is that it is brittle and dense which makes it difficult to work with it.
Below are the some types of glass with their properties and uses and with special additives in it is given in the table: