Plastics did not enter our lives with the tantare of other revolutionary inventions,but more by the process of infiltration.Plastics being synthetic materials were at first considered to be cheap substitute for the better known and more expensive materials.Plastic articles are not only replacing wood,metal and other materials for specific purposes.Through the years plastics have carved the right as materials themselves and not as subtitute for other materials.Not only are plastics more useful,Adoptable and practical than the materials they have supplemented,but uses for plastics have been found which no other material can be used.
Every year millions of tons of plastic materials are consumed throughout the world.
Plastics can be divided into two main groups,thermoplastics and thermoset plastics.
The thermoplastics are heated and brought to a plastic stage in an injection moulding machine.The machine injects the plastic into the metal mould,Where it is cooled.After solidification of the plastic the mould is opened and the component is ejected.This process is called injection moulding.
The other main process which utilises thermoplastics is blow moulding.Hollow articles such as jerry cans,containers(bottles) for liquids,toys etc... are made by blow mouldins.
For thermosetting plastics the two main methods used are compression moulding and transfer moulding in this process the thermoset material in powder or pallet form is kept inside the mould and is subjected to heat pressure.The powder melts and takes the shape of the mould and gets cured.Then the mould is opened and the component is ejected.