Preparation and Uses of Some Important Polymers:
Polyethene or Polyethylene:
It is an addition polymer of ethylene. On a commercial scale, it is obtained by heating ethene (CH2 = CH2) to 473K under high pressure (1500 atmospheres) in the presence of 0.03-0.10% of molecular oxygen.
It is used-
- In electrical insulators.
- In the manufacture of pipes and various engineering and domestic articles.
- As a packaging material in the form of thin plastic films, bags etc.
- In coats, bread wrappers etc.
Polypropylene or Polypropene:
It is an addition polymer of propene or propylene. It is generally manufactured by passing propylene through n-hexane (inert solvent) containing Zeigler-Natta catalyst (mixture of Triethyl aluminium i.e. Al (C2H5)3 and Titanium Chloride i.e. TiCl3).
It is harder and stronger polymer than Polyethene and is used-
- In packing textile material and food.
- In the manufacture of pipes, ropes, bottles, fibres, seat covers etc.
- For making heat-shrinkable wraps for records and other articles.
It is an addition polymer of styrene. It is prepared by the polymerisation of styrene in the presence of benzoyl peroxide.
It is a good transparent polymer and is used for making plastic toys, household wares (food containers, cosmetic bottles), TV cabinets, plastic cups, refrigerator linings, electrical insulation etc.
Polyvinyl Chloride (PVC):
It is an addition polymer of vinyl chloride. It is prepared by heating vinyl chloride in an inert solvent in the presence of benzoyl peroxide as an initiator.
It is a tough flexible material and is used-
- In the manufacture of raincoats, handbags, plastic dolls, curtain clothes and vinyl flooring.
- As an insulator in electric wires and other electrical goods.
- In the production of gramophone records, toys and other leather-like clothes.
Polytetrafluoro Ethylene (Teflon):
It is an addition polymer of tetrafluoroethene and is prepared by heating tetrafluoroethylene under pressure in the presence of Ammonium peroxosulfate i.e. (NH4)2S2O8.
It is a tough material and is resistant to the attack of acids, bases and heat. It is used-
- In coating utensils to make them non-sticky.
- In making seals and gaskets which can withstand high pressure.
- As an insulator for high-frequency electrical installations.
Terylene or Dacron:
It is a condensation polymer of Ethylene glycol and Terephthalic acid. It is prepared by heating ethylene glycol and terephthalic acid at about 425-475 K.
It is resistant to the attack of chemical reagents, wrinkling, wetting, pests and has high tensile strength. It is used-
- In the manufacture of ropes, safety belts, tents and sails.
- As a blend with cotton and wool in clothes to increase their resistance to wear and tear.
- In the preparation of films, magnetic recording tapes.
It is a copolymer of Adipic acid and Hexamethylene diamine. It is prepared by the condensation polymerisation of Adipic acid with Hexamethylene diamine at about 553K.
It is tough, flexible, resistant to most of the chemicals and has very high tensile strength. It is used-
- In the production of bristles for brushes.
- In the manufacture of socks, stockings, parachutes, carpets etc.
It is obtained by the condensation polymerisation of Ethylene glycol and phthalic acid.
It is thermoplastic and is used in the manufacture of paints and lacquers.
It is prepared by the condensation polymerisation of melamine (2,4,6-Triamino-1,3,5-Triazine) with formaldehyde.
It is used in the manufacture of unbreakable plastic crockery like cups, plates etc.