Chapter 3: Synthetic fibres and plastics

These NCERT Class 8 Science Chapter 3 notes explain synthetic fibres and plastics in a clear and structured manner. The chapter focuses on how synthetic fibres are made from chemicals derived from petroleum.

It discusses important concepts like polymers and monomers, different types of synthetic fibres such as rayon, nylon, polyester and acrylic, and various types of plastics. It also explains thermoplastics, thermosetting plastics and environmental concerns related to plastic waste.

Chapter 3 – Synthetic Fibres and Plastics is important for understanding modern materials and their impact on the environment. It is highly relevant for school examinations and foundation level competitive preparation.

Preparing for UPSC or BPSC? Strengthen your basics with our complete NCERT Book Notes PDF for Class 6–8, available inside the free foundation course.

👉 Access Complete NCERT Book Notes PDF

1. Introduction: what are synthetic fibres?

• Synthetic fibres are man-made fibres prepared in factories.
• They are made using chemicals obtained mainly from petroleum.
• These fibres are also called artificial fibres.
• Unlike cotton and wool, they do not come directly from plants or animals.
• Nylon shirts and polyester clothes are common examples of synthetic fibres.

2. What is a fibre?

• A fibre is a thin, thread-like structure used to make fabrics.
• Fibres are spun into yarns and then woven to form fabric.
• Fibres are of two main types: natural and synthetic.
• Natural fibres include cotton and wool obtained from plants and animals.
• Synthetic fibres include nylon and polyester made by chemical processes.

3. Synthetic fibres as polymers

• Synthetic fibres are made of polymers, which are large molecules.
• A polymer means many small units joined together.
• The small repeating units are called monomers.
• For example, polythene is made from many ethene units.
• Polymer structure gives synthetic fibres strength and flexibility.

4. Types of synthetic fibres

• There are four main types of synthetic fibres: rayon, nylon, polyester and acrylic.
• Each type has different properties and uses in daily life.
• These fibres are chosen based on strength, cost and durability.
• Some are substitutes for natural fibres like silk and wool.
• They are widely used in clothing and household materials.

5. Rayon as artificial silk

• Rayon is made from wood pulp, so it is not fully synthetic.
• It looks like silk and is therefore called artificial silk.
• Rayon is used in sarees, curtains, bed sheets and carpets.
• It absorbs moisture and is comfortable to wear.
• Rayon becomes less durable when wet.

6. Nylon as a strong synthetic fibre

• Nylon was the first fully synthetic fibre.
• It is strong, elastic and lightweight.
• Nylon is resistant to wear and tear and dries quickly.
• It is used in ropes, parachutes, fishing nets and seat belts.
• Mountaineers prefer nylon ropes because they are strong and light.

7. Polyester and its uses

• Polyester is made from repeating units of esters.
• A popular polyester fabric is terylene.
• Polyester is wrinkle-free, durable and easy to wash.
• It is used in dress materials, curtains and PET bottles.
• Polyester blends are commonly used in daily clothing.

8. Acrylic as artificial wool

• Acrylic is an artificial substitute for wool.
• It is warm and suitable for cold regions.
• Acrylic fibres are lightweight and cheaper than wool.
• They are used to make sweaters, blankets and shawls.
• Acrylic does not shrink as easily as wool.

9. Characteristics of synthetic fibres

• Synthetic fibres are strong and have high durability.
• They are lightweight and easy to maintain.
• Most are wrinkle resistant and dry quickly.
• They are generally cheaper than natural fibres.
• They are available in a wide variety of colours and designs.

10. Plastics as synthetic materials

• Plastics are synthetic materials made from polymers.
• They are widely used in almost every part of daily life.
• Plastics can be moulded into different shapes easily.
• They are used in containers, furniture and packaging.
• Plastics have replaced many traditional materials.

11. Types of plastics

• Thermoplastics soften on heating and can be reshaped repeatedly.
• Examples of thermoplastics include polythene and PVC used in bottles and wire insulation.
• Thermosetting plastics do not soften on heating and cannot be reshaped.
• Examples of thermosetting plastics include bakelite and melamine used in switches and kitchenware.
• The difference depends on how their polymer chains are arranged.

12. Properties of plastics

• Plastics are generally non-reactive, so they do not corrode easily.
• They are lightweight yet strong.
• Plastics are poor conductors of heat and electricity.
• They are resistant to chemicals and water.
• These properties make plastics useful in many applications.

13. Plastics and environment

• Plastics are non-biodegradable, meaning they do not decompose naturally.
• They cause soil and water pollution.
• Plastic waste harms animals and marine life.
• Plastic bags clog drains and create sanitation problems.
• Excessive use of plastics leads to environmental imbalance.

14. 4R principle to reduce plastic pollution

• The 4R principle stands for refuse, reduce, reuse and recycle.
• Refuse means avoiding unnecessary plastic use.
• Reduce means minimising plastic consumption.
• Reuse means using plastic items again instead of throwing them away.
• Recycle means converting plastic waste into new useful products.

15. Key exam-oriented keywords explained

• Synthetic fibres: Man-made fibres prepared using chemicals from petroleum.
• Polymer: Large molecule formed by joining many small repeating units.
• Monomer: Small unit that combines with others to form a polymer.
• Rayon: Artificial silk made from wood pulp.
• Nylon: First fully synthetic strong and elastic fibre.
• Polyester: Synthetic fibre made from ester units, used widely in fabrics.
• Acrylic: Artificial wool used for winter clothing.
• Plastics: Synthetic polymer materials that can be moulded into shapes.
• Thermoplastic: Plastic that softens on heating and can be reshaped.
• Thermosetting plastic: Plastic that does not soften on heating.
• Non-biodegradable: Substances that do not decompose naturally.
• 4R principle: Method to reduce plastic pollution by refuse, reduce, reuse and recycle.

16. One-page summary for quick revision

• Synthetic fibres are man-made polymers derived from petroleum.
• Main types include rayon, nylon, polyester and acrylic.
• Plastics are widely used due to their useful properties.
• Plastics are non-biodegradable and cause environmental problems.
• Following the 4R principle helps reduce plastic waste.

Understanding NCERT Class 8 Science Chapter 3 is essential to learn about man-made fibres and plastics used in daily life. The chapter clearly explains their properties, uses and environmental consequences.

The concepts help students understand non-biodegradable waste, recycling and the 4R principle. It is highly useful for school exams and foundation competitive preparation.

Continue reading NCERT Class 8 Science Chapter 4 – Materials: Metals and Non-Metals to understand physical and chemical properties of materials.

FAQs

Q1. What are synthetic fibres?
Synthetic fibres are man-made fibres prepared from chemicals, usually derived from petroleum.

Q2. What is a polymer?
A polymer is a large molecule formed by joining many small units called monomers.

Q3. What is the difference between thermoplastics and thermosetting plastics?
Thermoplastics soften on heating and can be reshaped, whereas thermosetting plastics do not soften once they are set.

Q4. Why are plastics harmful to the environment?
Most plastics are non-biodegradable and cause soil and water pollution because they do not decompose easily.

Q5. Why is this chapter important for exams?
It explains polymers, plastics and environmental issues, which are important for school exams and foundation level competitive preparation.

---