Discuss important properties and uses of Rubber.
Rubber: It is polymeric material along with high elastic yield strain. The various types of rubber materials are given as- Natural rubber, Synthetic rubber and Hard rubber.
Natural Rubber- This rubber is extracted from milky sap collected from particular trees. Water is after evaporated. Additives as oxidation inhibitors as aromatic amino compounds, sulphur, softeners as vegetable oil as well as fillers as carbon black and also zinc oxide are added to this. This is vulcanized by adding sulphur and heating this. Vulcanization improves heat and frost resistance of rubber, making this mechanically stronger. The power factor and permittivity varies depending upon the sulphur content and temperature change.
Properties - Natural rubber is moisture repellent and consists of good insulating properties. This has good abrasion resistance.
Applications - This is used for the manufacturing of protective clothing as gloves and boots. This is used as an insulation covering for cables and wires.
Hard Rubber - Hard rubber is acquired by addition of more sulphur and through extended vulcanization.
Properties - This has good electrical properties. There water absorption is less. Maximum permissible operating temperature is 600C. This cannot be continuously exposed to Sun as this is harmful. This has high tensile strength.
Applications - This rubber is used for construction of panel boards, storage battery housing and bushings of different types. This is also used for jacketing material for cables.
Synthetic Rubber - The various types of synthetic rubber are
(a) Butadiene rubber- Properties of butadiene rubber are greater resistance to ageing and lower tensile, oxidation and tear strength, higher heat conductivity and lower water absorption.
(b) Butyl rubber- Properties of Butyl rubber are excellent resistance to vegetable oils and alcoholic solvents, although this is easily attacked through petroleum oils and greases. This has high resistance to ozone, oxidation stability and high thermal but poor tensile strength. This is used as insulation for cables and wires.
(c) Chloroprene Rubber (Neoprene Rubber) - This has better resistance to thermal ageing, sunlight, gas diffusion and oxidation. Such rubbers have better thermal conductivity and extra flame resistance. They exhibit improved adhesion to metals. They possess better resistance to attack through solvents as mineral and vegetable oils although poor resistance to aromatic hydrocarbon liquids. Neoprene Rubber is inferior in mechanical properties as tear and abrasion resistance and tensile strength. It is used as insulating material for cables and wires. This is also used as jacketing material for cables.
(d) Chlorosulphonated Polyethylene (Hypalon)- This has better electrical properties, high resistance to degradation while exposed to oxidation and high temperature. This can be operated at temperatures as high as 1500 C. This has poor solvent resistance to hydrocarbons. This is mechanically less tough. This is used as insulating material for cables and wires and also as jacketing material for cables.
(e) Silicon Rubber - This has high thermal conductivity. Silicon rubber's tensile strength is low, has good flexibility on low temperatures and resistant to ozone, severe atmospheric conditions and oxidation. This can be used over a broad range of temperatures by -1000 to 1500 C. This rubber is used as insulating material for cables and wires, in the manufacture of moulded parts, like coating material and an insulating tape.