Synthetic Fibres and Plastics
This page covers the types of synthetic fibres, the classification of plastics, and waste management for REET. REET has asked questions on this topic that test whether you can tell biodegradable and non-biodegradable materials apart and pick the right disposal method for each — not just recall the names of fibres.
- 2 questions in REET 2024
- Class 6-8 level content
- 10 min read
How REET actually asks this topic
To be upfront: REET 2024 carried two questions from this topic, and both were built around classifying and managing waste — not around memorising fibre names. The first question asked you to identify a biodegradable waste item (answer: cotton wool, because it is a natural fibre that decomposes). The second asked which kind of waste is best treated by recycling (answer: metallic waste). So REET is testing whether you understand the practical biodegradable/non-biodegradable classification and the correct waste-management method for each type — not just fibre trivia. That said, questions on the types of synthetic fibres, their sources, and the thermoplastic-thermosetting classification of plastics have also shown up in REET-level exams in earlier years, so prepare both halves of this topic thoroughly.
What are synthetic fibres?
Synthetic (man-made) fibres are produced mainly from petrochemicals through a chemical process. Small chemical units called monomers join together to form a long chain — a polymer — and that chain is what becomes the fibre. This is fundamentally different from natural fibres such as cotton, wool, and silk, which are obtained directly from plants or animals, without this chain-building chemistry.
Why plastic is used everywhere — and the property that makes it a problem
Plastic is also built from long polymer chains, much like synthetic fibres, and it is exactly this structure that gives it the properties that have made it useful in nearly every field today: it is lightweight, durable, resistant to rusting, chemically unreactive (non-reactive), can be moulded into almost any shape, and is relatively cheap. These same properties make plastic hugely popular for packaging, utensils, toys, and casings for electronic devices.
But that very unreactivity — the fact that plastic does not break down easily — is also its biggest environmental problem. Because it resists decomposition, plastic can remain in the environment for years or even decades, polluting soil and water sources and proving harmful to animals and other organisms that come into contact with it or accidentally ingest it.
Types of synthetic fibres
| Fibre | Source / characteristic | Main use |
|---|---|---|
| Rayon | Made from wood pulp (cellulose) through a chemical process; shiny and soft like silk — also called 'artificial silk' | Sarees, clothing |
| Nylon | The first fully synthetic fibre, made from coal, water and air; extremely strong, light and flexible | Rope, parachutes, socks, toothbrush bristles |
| Polyester | Made from repeating ester units; wrinkle-resistant and quick-drying — PET bottles are also made from this family | Clothing, plastic bottles |
| Acrylic | A cheap, light and durable substitute for wool, and easy to dye | Sweaters, blankets |
Types of plastic
| Type | Property | Example |
|---|---|---|
| Thermoplastic | Softens on heating and can be moulded into a different shape again and again | Polythene, PVC (polyvinyl chloride) — bags, bottles |
| Thermosetting plastic | Once moulded into shape, it does not melt on reheating — it breaks instead, and cannot be reshaped | Bakelite, melamine — electrical switches, utensils |
Biodegradable vs non-biodegradable materials
- Biodegradable
- Materials broken down naturally by microorganisms (bacteria, fungi) — such as cotton wool, paper, vegetable peels, and wool
- Non-biodegradable
- Materials that microorganisms cannot break down, so they persist in the environment for a long time — such as plastic, metal, and glass
Ways to manage waste
- Household and agricultural waste
- Most of this (vegetable and fruit peels, leftover food, straw) is biodegradable, so composting is the best and most eco-friendly way to deal with it
- Metallic waste
- Recycling is the best method, because metal can be melted down and reused repeatedly to make new objects without losing quality
- Medical waste
- Because of the risk of spreading infection, it is kept separate from ordinary waste and usually disposed of safely through special methods such as incineration
- Plastic waste
- Adopting the 3R principle is best — Reduce (use less), Reuse (use again), Recycle (process into new material); plastic should never be burnt in the open, because that produces toxic gases and increases air pollution
How to teach this to children
Classroom activity
Bring in small pieces of cloth from home (cotton, nylon, polyester) and have students read the fabric labels to identify natural versus synthetic fibres. It is also worth pointing out that reading the fibre content on a label is a genuinely useful life skill.
Teaching aids
Bring in a range of everyday items from home — paper, a plastic bag, a piece of metal, a vegetable peel, glass — and have students sort them into a table as biodegradable or non-biodegradable, then discuss the right disposal method for each.
Common misconception
Many students assume all plastics are equally harmful, or that all plastics can be recycled the same way, or that anything 'synthetic' is automatically 'fake' or inferior. Make it clear that thermoplastics can be remoulded while thermosetting plastics cannot — and that being synthetic does not automatically mean being harmful or low-quality: many synthetic fibres and plastics have become widely useful precisely because of properties like strength, lightness, and durability.
Assessment idea
Give students a list of eight everyday objects and ask them to classify each as biodegradable or non-biodegradable and name a suitable disposal method (composting, recycling, incineration) for each. Then discuss the answers as a class and go over any common mistakes again.
Memory trick / exam tip
A trick for thermoplastic versus thermosetting: the word 'thermosetting' contains 'set' — once it 'sets' into shape, it becomes permanent and never melts again (like an electrical switch). Thermoplastic, by contrast, behaves like plastic in the everyday sense — it can be reheated and reshaped again and again, like a polythene bag. For the fibres, remember: rayon comes from 'wood', nylon from 'coal-water-air', polyester shows up in both 'bottles and clothes', and acrylic is known as the 'substitute for wool'.
REET 2024 questions (with solutions)
Question 131
An example of biodegradable waste is
- Aप्लास्टिक
- Bधातु
- Cकाँच
- Dरूई
Explanation
जो पदार्थ जीवाणु, कवक आदि सूक्ष्मजीवों द्वारा प्राकृतिक रूप से अपघटित हो जाते हैं, वे जैव-निम्नीकरणीय (biodegradable) कहलाते हैं। रूई (कपास) पौधे से प्राप्त प्राकृतिक रेशा है, इसलिए यह अपघटित हो जाती है। प्लास्टिक, धातु और काँच सूक्ष्मजीवों द्वारा अपघटित नहीं होते।
Question 127
Which waste is the best treated by recycling ?
- Aघरेलू अपशिष्ट
- Bकृषिय अपशिष्ट
- Cधात्विक अपशिष्ट
- Dचिकित्सकीय अपशिष्ट
Explanation
धात्विक अपशिष्ट (जैसे लोहा, एल्युमिनियम, तांबा) को पिघलाकर बार-बार नई वस्तुएँ बनाई जा सकती हैं और इससे गुणवत्ता में खास कमी नहीं आती, इसलिए इसका उपचार पुनर्चक्रण द्वारा सबसे उत्तम है। घरेलू व कृषि अपशिष्ट का बड़ा भाग जैव-निम्नीकरणीय होता है, जिसे कम्पोस्ट आदि से उपचारित किया जाता है, और चिकित्सकीय अपशिष्ट संक्रामक होने के कारण प्रायः भस्मीकरण जैसी विधियों से नष्ट किया जाता है।
Practice questions
Question 1
From which natural substance is rayon made?
- Aकोयला
- Bलकड़ी की लुगदी (सेलुलोज़)
- Cपेट्रोलियम
- Dरेशम कीट का रेशा
Explanation
Rayon is made by chemically treating wood pulp (cellulose), which is why it's also classed as a semi-synthetic fibre — and because of its silk-like sheen, it's known as artificial silk.
Question 2
Which was the first fully synthetic (man-made) fibre, made from coal, water and air?
- Aरेयॉन
- Bपॉलिएस्टर
- Cनायलॉन
- Dऐक्रिलिक
Explanation
Nylon was the first fully synthetic fibre, made from coal, water and air. Because it is extremely strong, it's used in parachutes, ropes, and socks.
Question 3
Which of the following is an example of a thermosetting plastic?
- Aपॉलिथीन
- BPVC
- Cपॉलिएस्टर
- Dबैकेलाइट
Explanation
Bakelite is a thermosetting plastic — once moulded, it cannot be reshaped by heating again; instead of melting, it breaks. That's why it's used for electrical switches and handles. Polythene and PVC, by contrast, are thermoplastics.
Question 4
Plastic water bottles (PET bottles) are mainly made from which synthetic material?
- Aरेयॉन
- Bनायलॉन
- Cऐक्रिलिक
- Dपॉलिएस्टर
Explanation
Plastic water bottles (PET bottles) are made from the polyester family of materials, which is light, strong, and wrinkle-resistant.
Question 5
Which of the following is an example of biodegradable waste?
- Aरूई
- Bकाँच
- Cप्लास्टिक
- Dधातु
Explanation
Cotton wool is a natural, plant-based fibre that microorganisms can break down, which is why it's biodegradable. Plastic, glass and metal are all non-biodegradable.
Question 6
The best method for disposing of metallic waste (like iron, aluminium) is:
- Aभस्मीकरण (जलाना)
- Bकंपोस्टिंग
- Cपुनर्चक्रण
- Dभूमि में दबाना
Explanation
Metallic waste can be melted down repeatedly to make new objects without losing quality, which is why recycling is the best way to dispose of it.
Question 7
The main reason open burning of plastic waste harms the environment is:
- Aयह कोई गंध नहीं छोड़ता
- Bइससे विषैली गैसें उत्पन्न होती हैं
- Cयह जल्दी अपघटित हो जाता है
- Dइससे कोई हानि नहीं होती
Explanation
Burning plastic waste releases toxic gases such as dioxins, which cause air pollution and are harmful to health — which is why plastic waste should never be burnt in the open.
Question 8
The acrylic fibre is mainly considered a cheaper alternative to which natural fibre?
- Aऊन
- Bरेशम
- Cकपास
- Dजूट
Explanation
Acrylic is light, warm, and cheap, which is why it's treated as an affordable substitute for wool and is used to make sweaters and blankets.
Question 9
The most suitable way to teach class 8 students the classification of biodegradable and non-biodegradable substances is:
- Aकेवल परिभाषा श्यामपट्ट पर लिखना
- Bघर से लाई वस्तुओं को छाँटकर तालिका बनवाना
- Cपाठ्यपुस्तक रटवाना
- Dकेवल चित्र दिखाना
Explanation
When students sort familiar objects they've brought from home (paper, plastic, peels, bits of metal) themselves, they discover and understand the basis for classification — which sticks far better than simply memorising a definition.
Question 10
The '3R' principle for responsible use and disposal of plastic includes:
- AReduce, Reuse, Recycle
- BRepair, Replace, Reuse
- CRemove, Reduce, Refuse
- DRecycle, Repair, Replace
Explanation
The 3R principle — Reduce (use less), Reuse (use again) and Recycle (process into new material) — is the standard strategy for managing plastic waste responsibly.
Frequently asked questions
What is the difference between synthetic and natural fibres?+
Natural fibres (cotton, wool, silk) are obtained directly from plants or animals, while synthetic fibres (rayon, nylon, polyester, acrylic) are man-made from petrochemicals through a chemical process.
Why is rayon called artificial silk?+
Rayon is made from wood pulp (cellulose) through chemical treatment, and its sheen and texture closely resemble natural silk — which is why it is called artificial silk.
What is the difference between thermoplastic and thermosetting plastic?+
Thermoplastic (like polythene) can be reheated and reshaped again and again, while thermosetting plastic (like Bakelite) breaks rather than melts once it has been moulded, and cannot be reshaped a second time.
Plastic is non-biodegradable — so why is it still so popular?+
The structure of plastic's polymer molecules is such that microorganisms cannot break them down, so it stays in the environment for years. Even so, it is light, durable, rust-resistant and cheap, which makes it useful everywhere from packaging to electronics — which is exactly why using and disposing of it responsibly (the 3R principle) matters. Note that cellulose-based fibres like rayon can decompose relatively quickly, while fully petrochemical fibres like nylon and polyester are considered practically non-biodegradable.
Which waste is best handled through recycling?+
Metallic waste (iron, aluminium, copper) is best handled through recycling, because it can be melted down repeatedly to make new objects without losing quality — this was asked directly in REET 2024.
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Change Log
- 17 September 2026 — English page published — mirrors the fact-checked Hindi page, independently bilingual-accuracy checked