Polymers – An Environmental Hazard:
Polymers are the indispensable part of our lives today. Notwithstanding the plethora of uses of all-pervasive polymers, they, being non-biodegradable pose a serious environmental hazard.
There are two major varieties of polymers. Natural polymers and man-made or synthesised polymers. Natural polymers form an integral part of our lives. We eat starch, a polymer consisting of many molecules of glucose joined together. The carbohydrate polymer in wood is cellulose, which is similar to starch except that its glucose molecules are joined together in a different manner. The wool fibres obtained from sheep and silk fibres spun by silkworms are also natural polymers. Basically, a polymer is a large molecule composed of many smaller repeating units. These repeating units of the polymer are known as a ‘monomers’. It was Berzelius who coined the name `polymer’ in 1827.
Polymers are found in nature and can also be synthesized using organic and inorganic compounds. The organic compounds that we find in nature are cellulose and rubber. The first synthetic polymer was made in 1838 when vinyl chloride accidentally polymerized giving polyvinyl chloride (PVC). It is a useful compound to make water pipes and other plastic materials. Nitrocellulose, the first synthetic derivative of a polymer was made in 1847 by Schonbein.
Today we are completely surrounded by synthetic polymers. We wear clothes of nylon and polyester, we walk on the polypropylene carpets, the cars we drive are made up of plastic and the tyres are made of synthetic rubber. Teflon’s (tetrafluoroethylene) which is used to make the coating on utensils and non-stick vessels is a derivative of ethylene. It is also used for making artificial pearls. Even artificial hearts and other organs are, in fact, made of silicon polymers. Rubber is a natural polymer.
The natural rubber was first used by Joseph Priestly who used the crude material to `rub out’ errors in his pencil writings. Hence it is given the name ‘rubber’. Natural rubber becomes soft and sticky in summer and hard and brittle in winter. It has also unpleasant odour and can be softened and dissolved in various solvents. However, Charles Goodyear found that by special heat treatment with sulfur, rubber can be converted into a tough, elastic, heat and cold stable substance. The process is called vulcanization, which is used in the making of tyres and various other products.
As there was increased demand for rubber, an alternative had to be found. In 1900 Kondakor produced a synthetic form of rubber. One of the first synthetic polymers to find a commercial use was ‘neoprene’, discovered by Collins and -Carothers at Dupont. It is useful in making insulation, conveyor belts, weather balloons etc.
An elastomer — a synthetic polymer with great elasticity is used in making automobile tyres. The simplest polymer is the polymer of 1,3 butadiene which is synthesized using the Zigler-Natta Catalyst. This catalyst is named after the scientists Karl Zigler and Giulio Natta who discovered its formation in 1953. In 1963 the two scientists received the Nobel Prize for their work, which had revolutionized the polymer industry in only ten years.
Natural and Synthetic Fibres:
Probably Leather was the first polymer and wool was the first fibre used by man for clothing. The textile industry uses natural fibres such as cotton, flax, wool and silk. Synthetic fibres are nylon, polyester, acrylic etc. Efforts were made to modify the short cellulose fibres obtained from the wood into longer fibres like cotton or silk. This resulted in a fibre called rayon. Rayon was the first man-made fibre to be produced commercially.
Wallace Carothers of Dupont discovered nylon in 1938.He opened the door for a new age of fibres and textiles. Unlike the weak animal and plant fibres, nylon is very strong fibre. Polyester is another important man-made fibre which is important for wrinkle-free cloth manufacturing. It is discovered in 1940.
Polyethylene – Non-biodegradable Polymer:
Polyethylene Polymer has revolutionized the packaging industry since it was invented_ It can be both transparent and coloured. It is used iii making carry bags. An excessive, use of it is an environmental hazard as it is a non-biodegradable polymer. It simply means that it cannot be completely destroyed from the environment. When you burn it, it leaves another polymer liquid. Also, it cannot be dissolved in any organic or inorganic liquid. It can only be recycled for reuse. Since it cannot be destroyed, millions of tons of this waste is a matter of grave concern. The only remedy is to decrease its use by switching over to other options available such as using cloth or jute bags as packaging material.