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Plastics - Lesson Summary

Plastics are polymers of long carbon chains. They consist of very long molecules each composed of carbon atoms linked in chains. Fossil fuels contain hydrocarbons (compounds containing hydrogen and carbon), which provide the building blocks for long polymer molecules. These small building blocks, called monomers, link together to form long carbon chains called polymers.
These monomers can be linked in linear manner to form linear polymers and linked cross linked manner to form cross linked polymers.

Depending on this physical property, plastics are categorized into two types: Thermoplastics and Thermosetting plastics.

Plastics that get deformed easily on heating and can be bent easily are known as thermoplastics. Most of the linear polymers or combination of linear and cross-linked polymers are thermoplastics.
Example: PVC, polythene, nylon, acrylic, celluloid and cellulose acetate

Thermosetting plastics
Plastics which when moulded, cannot be softened by heating are called thermosetting plastics. Heavily cross linked polymers are the thermosetting plastics.
Example: Bakelite, melamine, vulcanised rubber, duroplast and epoxy resin

Characteristics of plastics
       •  Plastics do not corrode easily
       •  Plastics can carry easily as they are low weight materials.
       •  Plastics are strong and durable.
       •  Plastics can be easily moulded into different shapes and sizes.
       •  Plastics are poor conductors of heat and electricity. Thus used to make handles of cooking vessels.

Uses of plastics

         Plastic                                         Uses Polythene Used for preparing polythene bags, pipes, buckets, and unbreakable bottles. Acrylic Used for making window panes of cars and trucks. Polypropylene Used for making ropes, fibres, and popes. Styrene Used for making acid caps, cases of voltaic cells, etc. Teflon Used in making non- sticky pans. Melamine Used in making vessels. Bakelite Used for making switches, plugs, combs, handles, etc. Celluloid  Used for making photographic films, combs and soap boxes. PVC (poly vinyl chloride) Used in food packaging, making of sanitary pipes. LDPE (Low density polyethylene) Used making of in food bottles and packaging of foods, polybags. HDPE (High density polyethylene) Used in making food and drink containers and in making of containers which are used in laboratory to store chemicals. PET (polyethylene terephthalate) Used in beverage bottles and food containers.

Plastic has a wide variety of uses in our day to day life.

Household appliances
Special plastic is used in the making of cookware used in microwave ovens for cooking food. In microwave ovens, the heat cooks the food but does not affect the plastic vessel. Teflon coating is another plastic which is used in non-stick cook ware. Teflon is a special plastic on which oil and water do not stick.

Health care
The packaging material of tablets, syringes, threads used for stitching wounds and doctor gloves etc are made of plastics.

The interior parts of a car like the dash board, and some other parts of helicopters and aeroplanes are made of plastic.

Harmful effects of plastics

Polythene bags are non-biodegradable and cause environmental pollution. Burning of plastics produce large amount of smoke which cause environmental pollution. They undergo a process known as photo degradation, in which they break down into smaller and smaller toxic particles. These particles contaminate soil and water and end up entering the food chain when eaten accidentally by animals like cows. In addition polythene bags can choke cattle to death. Hundreds and thousands of whales, dolphins, sea turtles and other marine mammals die every year after consuming discarded polythene bags.
Polythene bags are also responsible for the clogging of drainage systems in cities and towns. Plastics take several years to decompose. Thus, to save environment we should use plastic properly and avoid their misuse.


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