What is PLASTIC? “The plastic is anorganic substance and it consists of natural or synthetic binders or resins with or without moulding compounds.”
“Plastics are compounds ofcarbon with other elements such as hydrogen , nitrogen , oxygen.” “Plastics are polymers.”
Theyprove to be economical as compare to other conventional materials. They should not be bent too much to avoid any stresses in them. They are available in various colours, but it is advisable to avoid red and black colours on external expose surfaces. They should provide wood heat resistance .
They should not be affected by chemicals , salts, acids easily.Their shape and size should not be distorted easily. Their colours should not be fedded easily. They should durable with good resistance to cracks and breaks. They should possess good strength.
“THERMOPLASTIC IS A POLYMERTHAT TURNS INTO A LIQUIDWHEN HEATED AND FREEZESINTO A VERY GLASSY STATEWHEN COOLED SUFFICIENTLY.”
They have linear or chain structure. They are produced by addition polymerisation.Ex: Acrylic, PVC, polystyrene, polyethelene, nylons,etc.
This plastic has cross linked or network structure. It is produced by condensation polymerisation. This plastics need a large prssure and momentary heat while moulding which becomes hard on cooling. remoulding is impossible .
Compare to thermoplastics , this have high strength. Telephone receivers, radio & T.V cabinets, camera body’s , switches, circuit breakers etc are made from thermosetting plastic.Ex : Bakelite, epoxy, polyesters, melamines, etc.
It is light in weight.Specific gravity of plastic is 1.40.It is easy to cast , mould , blow, saw, drill. It has good machinability.It is easy to fix them in any position.They have high tensile and compressive strength.They have low thermal conductivity.They have low electrical conductivity.They can absorb shocks.They are free form corrosion .They are no attacked by vermin, insects, etc.They can be manufactured in wide range of colours.It is possible to manufactured plastic colourless and transparent as well as non transparent.
They are use to make:- Furniture like sofa , table , chair,etc. Optical lenses, spectacles, frames. Handles of tools cases of machines , covers. Electrical and heat insulators , electrical appliances and accessories. Cooking wears, table wears. Water proof doors, bags. Sanitary fittings like taps , pipes, valves etc.