PLASTICS – Types and uses of plastic
Plastic was introduced during the 19th century by the industrialists. Plastic is one of the recent engineering materials. This is available in the market all over the world. Plastic is an organic substance and it consists of natural or synthetic binder or resins with or without moulding compounds.
USES OF PLASTICS
Plastics are used in the manufacture of following materials
i. Bath and sink units
ii. Corrugated and plain sheets
iii. Decorative laminate and mouldings
iv. Electrical conduits
v. Electrical insulations
vi. Floor mates
vii. Lighting fixtures viii. Paint and varnish
ix. Pipes to carry cool water
TYPES OF PLASTICS
The property of plastics can be changed due to increase or decrease in temperature. Based on that the plastics are classified into two types
1. Thermoplastics
2. Thermosetting plastics
1. THERMOPLASTICS: These plastics become soft when heated and hard when cooled. Thus it is possi- ble to shape and reshape these plastics by heat and pressure as the process of softening and hardening may be repeated for an indefinite time unless the heat is not so high causing chemical decomposition. The main advantage is old scrap materials can be used again and again.
2. THERMOSETTING PLASTICS: This plastic become rigid when moulded at suitable pressure and temperature. When they are heated to the temperature range of 127° C to 177° C they set permanently and further application of heat does not alter their form or soften them. The thermosetting plastics are soluble in alcohol and certain organic sol- vents. The thermosetting plastics are strong, durable and hard and are available in various colours and are also used in engineering applications.