Plastics and man-made fibres are all around us - in bottles, bags, clothes and pipes. Exams ask fixed questions about them: what a polymer is, which plastic is used for non-stick pans, which fibre is called artificial silk, who made the first plastic. This post explains polymers, plastics and synthetic fibres in simple words, followed by 15 previous year questions.
Key Points (Quick Revision)
- A polymer is a long chain made of many small units called monomers.
- Thermoplastics soften on heating; thermosetting plastics (bakelite, melamine) do not.
- Bakelite was the first fully man-made plastic, made by Leo Baekeland in 1907.
- Nylon was the first fully synthetic fibre. Rayon is called artificial silk.
- Teflon is used for non-stick pans. Vulcanisation hardens rubber with sulphur.
1. What a polymer is
Think of a chain made of many paper clips joined together. Each clip is a small unit. The whole chain is a big unit. In chemistry, the small unit is called a monomer, and the long chain made of many monomers is called a polymer. "Poly" means many, and "mer" means part.
The process of joining monomers into a polymer is called polymerisation.
Some polymers are made by nature. Others are made in factories.
| Type | Examples |
|---|---|
| Natural polymers | Cellulose (in cotton and wood), starch, proteins (in silk, wool, hair), natural rubber |
| Synthetic polymers (man-made) | Polythene, PVC, nylon, polyester, Teflon, bakelite |
A common question: cotton is made of cellulose, while silk and wool are made of protein. Both are natural polymers.
2. Two kinds of plastic
| Type | What happens on heating | Examples and uses |
|---|---|---|
| Thermoplastics | Soften when heated and can be re-shaped many times | Polythene (bags), PVC (pipes), polystyrene (packing) |
| Thermosetting plastics | Do not soften once set; heating burns them instead | Bakelite (switches, pan handles), melamine (crockery, fire-resistant) |
This is why electric switches and cooker handles are made of bakelite - it does not melt with heat and it does not carry electricity. And melamine is used in kitchen plates and in fire-resistant uniforms because it resists heat and fire.
3. Common plastics and their monomers
| Plastic | Made from (monomer) | Used for |
|---|---|---|
| Polythene | Ethylene | Carry bags, packing film, bottles |
| PVC (polyvinyl chloride) | Vinyl chloride | Water pipes, electric wire covering, raincoats |
| Teflon | Tetrafluoroethylene | Non-stick coating on pans |
| Polystyrene | Styrene | Thermocol, packing, disposable cups |
| Bakelite | Phenol and formaldehyde | Switches, handles, electrical fittings |
| Natural rubber | Isoprene | Tyres (after vulcanisation), rubber goods |
Two of these are asked most often. Teflon for non-stick pans, because food does not stick to it and it can take heat. And isoprene is the monomer of natural rubber.
Vulcanisation is also a favourite question. Natural rubber is soft and sticky, and it becomes hard in cold and soft in heat. Charles Goodyear found in 1839 that heating rubber with sulphur makes it strong and elastic. That process is vulcanisation, and it is why tyres last.
4. Synthetic fibres
Fibres are thin threads used to make cloth. Cotton, wool and silk are natural. Many fibres today are made in factories.
| Fibre | Simple fact | Used for |
|---|---|---|
| Rayon | Made from wood pulp (cellulose); called artificial silk | Clothes, bedsheets |
| Nylon | The first fully synthetic fibre; very strong | Ropes, parachutes, socks, fishing nets |
| Polyester | Does not wrinkle easily; Terylene is a common polyester | Shirts, sarees; PET bottles are also polyester |
| Acrylic | Called artificial wool; cheaper than wool | Sweaters, shawls, blankets |
Keep these three pairs clear: rayon - artificial silk, acrylic - artificial wool, nylon - first fully synthetic fibre. Rayon is sometimes called semi-synthetic, because it starts from natural wood pulp and is then treated with chemicals.
Synthetic fibres dry fast and last long. But they melt on heating and stick to the body, so it is safer to wear cotton in the kitchen or near fire.
5. Plastics and the environment
Most plastics are non-biodegradable. This means bacteria cannot break them down, so they stay in soil and water for hundreds of years. Things like vegetable peels and paper are biodegradable - they rot and mix back into the soil.
Plastic waste blocks drains, harms animals that swallow it, and spoils soil. Burning plastic gives out poisonous gases.
What helps:
- Reduce, Reuse, Recycle - use less plastic, use items again, and send plastic for recycling.
- Cloth or jute bags instead of polythene bags.
- India banned identified single-use plastic items from 1 July 2022 - such as plastic straws, cutlery and earbuds with plastic sticks.
Recycling signs on plastic items carry a number inside a triangle, from 1 to 7. The number tells the type of plastic, so it can be sorted for recycling.
6. Previous year questions
- A polymer is made of many small units called what? — Monomers
- Which plastic is used for non-stick cookware? — Teflon
- What is the monomer of natural rubber? — Isoprene
- What is the monomer of polythene? — Ethylene
- Who made bakelite, the first fully man-made plastic? — Leo Baekeland, in 1907
- Which fibre is called artificial silk? — Rayon
- Which fibre is called artificial wool? — Acrylic
- Which was the first fully synthetic fibre? — Nylon
- Rayon is made from which natural material? — Wood pulp (cellulose)
- Heating rubber with sulphur to make it hard is called what? — Vulcanisation
- Who discovered vulcanisation? — Charles Goodyear
- Electric switches are made of which plastic? — Bakelite
- Plastics that do not soften on heating are called what? — Thermosetting plastics
- Cotton is made of which polymer? — Cellulose
- From which date did India ban identified single-use plastic items? — 1 July 2022
7. How to revise this topic
First, learn the words monomer, polymer, polymerisation and one example of each type: natural (cellulose) and man-made (polythene).
Next, learn the two kinds of plastic: thermoplastics soften, thermosetting do not. Bakelite and melamine are the two thermosetting names that come in exams.
Then learn the pairs by saying them out loud: Teflon - non-stick, PVC - pipes, rayon - artificial silk, acrylic - artificial wool, nylon - first synthetic fibre, isoprene - rubber, sulphur - vulcanisation.
Finally, keep the three names and years: Goodyear 1839, Baekeland 1907, and the single-use plastic ban of 1 July 2022.
8. Frequently Asked Questions
What is the difference between a monomer and a polymer?
A monomer is a small unit. A polymer is a long chain made by joining many monomers together. For example, ethylene is the monomer and polythene is the polymer made from it.
What is the difference between thermoplastics and thermosetting plastics?
Thermoplastics soften when heated and can be re-shaped many times, like polythene and PVC. Thermosetting plastics do not soften once set, and heating only burns them, like bakelite and melamine.
Why is Teflon used in non-stick pans?
Because food does not stick to it and it can take high heat without melting. It is a polymer made from tetrafluoroethylene.
Why is rayon called artificial silk?
Because it looks and feels like silk but is made in factories from wood pulp. Since it starts from a natural material, it is also called a semi-synthetic fibre.
Why are plastics harmful to the environment?
Most plastics are non-biodegradable, so bacteria cannot break them down. They stay in soil and water for hundreds of years, block drains and harm animals, and burning them gives out poisonous gases.
For more General Science topics in simple language, see our Carbon and Its Compounds and Important Alloys posts, or browse the General Science section. Preparing for a specific exam? Start with the SSC CGL guide or join the 100 Hour GS Course.