Introduction — Fibres and Plastics

Materials used to make clothing, containers and a vast range of consumer goods can be broadly grouped into fibres and plastics. Fibres are long, thin strands used mainly to make textile fabrics; plastics are synthetic materials moulded into shapes. In this chapter, we study synthetic fibres — man-made replacements for natural fibres — and plastics, their properties, uses and environmental impact. These notes strictly follow the NCERT syllabus and emphasise the concepts that are frequently tested in CBSE Class 8 examinations.

Natural Fibres vs Synthetic Fibres

Natural fibres like cotton, wool and silk come from plants or animals. They have been used for centuries and are biodegradable. Synthetic fibres are manufactured using chemical processes starting from natural materials (like cellulose) or petrochemicals. Synthetic fibres were developed to overcome limitations of natural fibres — for example, to obtain stronger, more elastic, or low-maintenance fabrics.

Key point: Synthetic fibres are engineered for specific properties — durability, elasticity, light weight and resistance to wrinkling — but many are derived from non-renewable petroleum resources.

Important Synthetic Fibres — Overview

Below are the main synthetic fibres discussed in the NCERT Class 8 Chapter 3, with their key features and common uses.

Rayon (Viscose)

Rayon is produced from regenerated cellulose (wood pulp). It resembles cotton or silk in feel and is often called an artificial silk. Rayon is comfortable and absorbent but wrinkles easily and is less strong when wet compared to some other synthetics. Uses: dress materials, linings, curtains.

Nylon

Nylon was the first fully synthetic fibre to become commercially successful. It is strong, elastic and resistant to abrasion. Nylon is used for stockings, ropes, parachutes, toothbrush bristles and synthetic fabrics blended with other fibres to increase strength.

Polyester

Polyester fibres are strong, resistant to most chemicals, and do not shrink easily after washing. Polyester is commonly used in clothing, home furnishings (curtains), and industry (seat belts, conveyor belts). Polyester blends (e.g., poly-cotton) combine comfort with durability.

Acrylic

Acrylic is light, warm and soft with wool-like properties. It is used in sweaters, blankets and as a wool substitute. Acrylic is resistant to moths and sunlight compared to natural wool.

Plastics — What They Are and Why They’re Useful

Plastics are a broad group of organic materials made of long chains of repeating units called polymers. They can be shaped into various forms and retain that shape. Plastics are inexpensive, light in weight, corrosion resistant and easily moulded. These properties make plastics suitable for packaging, toys, household goods, medical devices and components in automobiles and electronics.

Thermoplastics vs Thermosetting Plastics

• Thermoplastics: Soften on heating and can be remoulded multiple times (e.g., polyethylene, PVC, polystyrene). Their recyclability is generally higher because they can be melted and reprocessed.
• Thermosetting plastics: Harden irreversibly on heating and cannot be remoulded (e.g., bakelite, melamine resin). They are heat-resistant and used where rigidity and dimensional stability are required.

Example: Bakelite (a thermosetting plastic) is used for electrical switches and handles because it does not melt on heating and is a good electrical insulator.

Properties and Uses — Quick Reference

Understanding characteristic properties helps predict how fibres and plastics are used:

• Strength & Durability: Nylon and polyester are strong and used where wear resistance is needed.
• Elasticity: Nylon and certain polyester blends are elastic, useful in stockings and sportswear.
• Absorbency: Rayon is absorbent and comfortable for garments.
• Heat resistance: Thermosetting plastics resist high temperatures; useful in electrical fittings.
• Chemical resistance: Many plastics resist chemical attack, useful for containers and piping.

Exam tip: When asked to compare two materials, use a table format: property — material A — material B — example use. That structure is readable and scores well in exams.

Environmental Concerns and Responsible Use

While synthetic fibres and plastics offer many conveniences, they also raise environmental issues. Most synthetic plastics are not biodegradable and can persist in the environment, causing pollution. Synthetic fibres shed microplastics during washing, contributing to aquatic pollution. Burning plastics releases toxic fumes.

Reduce, Reuse, Recycle (3Rs)

Key strategies to reduce environmental impact:

• Reduce: Limit single-use plastics and choose products with minimal packaging.
• Reuse: Use cloth bags, refill containers and repair items instead of discarding them.
• Recycle: Sort plastics by type (look for recycling codes) and support waste segregation and recycling initiatives.

Class activity idea: Demonstrate recycling by collecting torn synthetic cloth or plastic wrappers and showing images or videos of recycling plants; discuss how thermoplastics are remelted and reformed.

Care of Synthetic Fabrics and Safe Use of Plastics

Caring for synthetic fabrics extends their life and reduces waste. Follow washing instructions on labels, avoid high-temperature ironing on thermoplastic-based fabrics, and use appropriate detergents. For plastics, avoid heating food in certain plastic containers unless they are labelled microwave-safe.

• Read care labels: Symbols guide washing, bleaching and drying.
• Prevent pilling: Wash garments inside out on gentle cycles.
• Safe disposal: Recycle or donate usable textiles; follow local guidelines for plastic disposal.

Simple Practicals and Demonstrations (NCERT aligned)

NCERT suggests simple classroom demonstrations to reinforce concepts. These are safe and easy under teacher supervision:

• Burning test (demonstration only): Show how cotton burns (leaves ash) while some synthetic fibres melt and produce a plastic-like smell. Emphasise safety: perform in a fume hood or open space with small samples and fire safety measures.
• Absorbency test: Compare water absorption in cotton, rayon and polyester to illustrate differences in hydrophilicity.
• Recycling discussion: Bring sample cleaned plastic containers with recycling codes and explain which types are commonly recyclable.

Safety note: Do not perform open flame tests without teacher supervision and proper safety equipment.

Important Definitions & Quick Notes

• Fibre: A long, thin thread used to make textiles.
• Synthetic fibre: A fibre made by chemical synthesis (e.g., nylon, polyester).
• Polymer: Large molecules formed by repeating units (monomers).
• Thermoplastic: A plastic that softens on heating and can be remoulded.
• Thermosetting plastic: A plastic that hardens irreversibly when heated.

Exam Tips & Revision Strategy

To prepare effectively for CBSE Class 8 questions on this chapter:

• Memorise definitions and list examples for each fibre and plastic type.
• Use short comparison tables (e.g., nylon vs cotton, thermoplastic vs thermoset) for quick revision.
• Remember common uses — linking property to application earns marks (e.g., 'nylon is used for ropes because it is strong and elastic').
• Practice one or two short experiments in class and be able to describe observations and conclusions.
• Revise environmental points — 3Rs, recycling codes and safe disposal — as these are frequently asked in application-based questions.

Summary (Concise)

Synthetic fibres and plastics are integral to modern life. Synthetic fibres like rayon, nylon and polyester provide durable, versatile textiles, while plastics offer cheap, mouldable materials for countless uses. Understanding their properties, applications and environmental impact is essential. Focus on definitions, characteristic properties and linking properties to uses for best exam outcomes. These study materials are designed strictly as per the NCERT syllabus, making them ideal for CBSE Class 8 board exams standard.