Plastic

This has gained immense popularity as engineering materials. These organic materials know also as polymers lack strength of metals and cannot stand temperature higher than 150°C till now they offer the benefits of convenient manufacturing into some shapes and sizes right from molten state. They can be machined, however cannot be formed from solid state as metals can be completed. The plastics have good surface finish; they are not corroded and are not biodegradable. Because of the last property the plastics are not easy to dispose off. These materials do not conduct electricity hence are utilized for making electrical fittings. They are bad also conductors of heat thus are utilized as insulators in and housing for instruments and equipment that produce heat inside. The low density is a strong property of plastic. Hence heaviest plastic has specific gravity of 2.3 against 7.8 of steel and 2.7 of aluminum. The plastic content of automobile has gradually raises from 12 kgf in 1960 to 100 kgf in 1980 and to 150 kgf in nineties. The plastic replaces some times its weight in metals and automobiles hence become lighter. The plastics offer benefits like low cost, elimination of finishing processes, simplify assembly, decreases of vibration and noise.

Polymers are classified into three broad divisions, namely: elastomers, plastics and fibers. Thermoplastic resins are generally revised to as plastics and have the property of increasing plasticity, which is capability to deform plastically along with increasing temperature. They contain long chain structure. Thermosetting resins on the other hand have three- dimensional network of primary bonds. It do not soften on heating, it become harder because of completion of any leftover polymerization reaction on heating.

Thermoplastics in common employ are low density and high density polyethylene, rigid chlorinated polyvinyl chloride or PVC, polypropylene. ABS, Acrylic and poly tetra-fluoroe-thylene or PTFE. Most of them have maximum employ temperature of about 100°C. Only PTFE can be utilized at higher temperature upto 250°C. This material is utilized for bearing. Polyethylene is utilized in automobile interiors. ABS is acronym for a family of thermoplastics made of acrylonitrile, butadiene and styrene. ABS is utilized for making body of business machine, telephone housing and pipe and fitting in drain waste.

Thermosetting plastics in large number are made and utilized in industry. It can resist little higher temperature than thermoplastics have higher insulation against heat and electricity and contain better dimensional stability. Malamine is extremely popular in consumer items -particularly dinner sets. Mainly of these plastics like phenolic, epoxy and malainin: are utlized as bonding agents in plywood and particle boards. Epoxy is favoured also coating surfaces for prevention of corrosion, enhancing surfaces and as primer on automobile body.

Elastomers are the materials that deform from double the length to ten times original length. Rubber is an elastomer, which is acquired in liquid form trees however converted into solid by process of vulcanisation. The employ of rubber as shock absorber or vibration damper is recognized styrene butadiene is an artificial rubber.