Silicones

Silicones are non-metallic elements in group 4 or carbon group. Though its pure form is highly reactive we can find various varieties of silicones in nature such as rocks, sand etc. Silicon combines with other elements to form different compounds that are useful in various levels of our lives. 

Properties of Silicones

• Silicones are poor thermal and chemical conductors and this is why they are used as insulators. 
• Compared to other substances, their toxicity level is very low.
• It is waterproof and can make watertight sealants. 
• It is highly resistant to oxygen, ozone, or UV light.
• It can also be an electric insulator.
• It is stable even at higher temperatures.
• It also possesses higher gas permeability. 
• Silicone makes superior solvents to be used with other organic compounds.
• When burned in the presence of oxygen, it forms solid silica such as silicon dioxide in the form of a white powder, char and other gases. 
• The white powder thus obtained is called silica fume.

Colour of Silicon

The pure form of silicon is crystalline with a dark grey in colour with a lustre on its surface. Its tetrahedral structure is similar to that of a diamond and shows similar physical and chemical properties.

Preparation of Silicones

Silicones are prepared from pure silicon by the reduction of silica, which is in the form of sand. It is usually treated with carbon at higher temperatures. The chemical reaction is represented as, 

SiO2(s) + 2C(s) → Si(s) + 2CO(g)

Silicones are made from silicon in three stages such as 

1. a) Synthesis of chlorosilanes
2. b) Hydrolysis of chlorosilanes
3. c) Condensation polymerization

Types Of Silicone

1. Silanes

Silanes are the homologous form of silicon hydrides. They are useful as highly effective reducing agents. They can burst into flames instantly when exposed to air. They are highly reactive and are unstable at room temperature.

1. Silicides

Silicides show similar structures to carbides and borides. Therefore, thermal generation is also with the carbides and borides of those elements.

1. Silica

Silica is silicon dioxide, the major constituent of granite and sandstone.

1. Halides

Silicon carbides or silicon when react with the stable halogens form silicon tetrahalides. Unlike carbon tetrahalides, these silicon tetrahalides are easily hydrolysed in water.  

1. Silicate Minerals

Silicate minerals constitute about 95% of the earth’s rocks. It also forms 28% of the mass of the earth’s crust.

1. Silicic Acids

It is a hydrated version of silica gel which is widely used in toothpaste. 

Use Of Silicon

• It is the major constituent of bricks and ceramics.
• Used for making transistors as a semiconductor. 
• Silicon is also widely used in solar cells and computer chips.
• Useful as the vital component of cement.
• In the making of fire bricks.
• For waterproofing systems.
• Silicon is used in moulding compounds.
• A major component of ferrosilicon – an alloy, used in the steel industry.
• Silicon is used as a sealant in aeroplanes due to its temperature sensitivity and high-stress resistance. 
• Silicone is commonly seen in kitchen utensils and bakeware. 
• Silicone is also used in exterior paintings. 
• Goggles and other diving goods are made of silicone due to their water repellent properties. 
• It is also used for making toys.