Class 8 Science – Synthetic Fibres and Plastics: Types and Uses

1. Introduction

• Synthetic fibres and plastics are man-made materials made by humans using chemical processes.

• They are alternatives to natural fibres and materials like cotton, wool, and wood.

• Widely used due to their strength, durability, and versatility.

Key Concept:

• Synthetic fibres and plastics are engineered for specific uses, unlike natural fibres.

2. Synthetic Fibres

• Synthetic fibres are man-made fibres obtained from chemical substances like petroleum.

• They are stronger, lighter, and more durable than natural fibres.

Common Types and Uses

1. Nylon

   • Strong, elastic, and resistant to wear.

   • Uses: Ropes, stockings, parachutes, carpets.

2. Polyester

   • Durable, resists shrinking and stretching.

   • Uses: Clothing, bedsheets, curtains, and ropes.

3. Acrylic

   • Soft, warm, and lightweight.

   • Uses: Sweaters, blankets, and artificial wool.

4. Rayon (Artificial Silk)

   • Soft and shiny like natural silk.

   • Uses: Dresses, shirts, sarees, and linings.

Key Concept:

• Synthetic fibres are chosen based on strength, texture, and resistance to water or wear.

3. Plastics

• Plastics are synthetic materials made from polymers.

• Lightweight, flexible, and resistant to corrosion and chemicals.

Common Types and Uses

1. Thermoplastics

   • Can be melted and reshaped multiple times.

   • Uses: Toys, pipes, bottles, and containers.

2. Thermosetting Plastics

   • Cannot be reshaped once set.

   • Uses: Electrical switches, handles of utensils, insulation.

3. Polyethylene

   • Light and durable.

   • Uses: Bags, bottles, and containers.

4. PVC (Polyvinyl Chloride)

   • Stiff and strong.

   • Uses: Pipes, window frames, and raincoats.

4. Advantages of Synthetic Fibres and Plastics

• Durable and long-lasting.

• Resistant to water, chemicals, and pests.

• Lightweight and easy to carry.

• Can be manufactured in various shapes, sizes, and colors.

• Reduce the need for scarce natural resources.

5. Disadvantages

• Non-biodegradable → cause pollution.

• Can clog drains and harm animals if not disposed properly.

• Some synthetic materials may release harmful chemicals when burned.

6. Key Points to Remember

• Synthetic fibres: Man-made fibres from chemicals → used in clothing, ropes, carpets.

• Plastics: Man-made polymers → used in packaging, household items, and industry.

• Advantages: Durable, versatile, water-resistant, lightweight.

• Disadvantages: Non-biodegradable, polluting, can harm the environment.

• Proper disposal and recycling are essential for environmental safety.