Chapter 3 :- Synthetic fibres and plastics Class 8 Notes

• Introduction
• Types of Synthetic fibers
• Characteristics/ Advantages of synthetic fibers
• Disadvantages of Synthetic fibers
• Plastics
• Properties & Uses of plastics
• Problems with excessive use of plastics

Introduction

• Man-made fibers and not derived from natural sources are called synthetic fibers. E.g. Nylon, rayon, polyester etc.
• Synthetic fibers and plastics are made up of molecules called polymers.
• A polymer is a large molecule formed by combination of many small molecules, each of which is called a monomer.
• The structure of polymer can be compared to that of bead neckless- the bead being the monomers.
• The process of combining the monomers to form a polymer is called polymerization.

Types of Synthetic fibers

• Rayon
• Nylon
• Polyester
• Acrylic are some synthetic fibers.

Rayon is made from wood (artificial silk) pulp, a naturally- occurring, cellulose- based raw material. Rayon is moisture-absorbent and comfortable to wear.
Uses of Rayon

• Home furnishings such as bedspreads, bed sheets, blankets, curtains, tablecloth, carpets etc. are made from rayon fiber, as it has a silky lustre.
• It is strong fibre, it is used in automobile tyre cords.
• It is used to make apparel such are suits, jackets, slacks etc.

Nylon was the first synthetic fiber to be made entirely from chemicals.

• Basic raw materials for the production of nylon are coal, petroleum oil, water and air.
• Nylon fiber is very strong and elastic.
• It is light and wrinkle- resistant.
• It is easy to wash and absorbs very little water.

• Garments such as saris are made from nylon. Since it is wear resistant, garments made from it last for a long time.
• Being very strong, nylon fiber is used to make ropes, tents, fishing nets and parachutes.
• It is also used to make toothbrushes, combs, zip fasteners and machine parts.

Polyester is a polymer of many ester units.

• Polyester is manufactured from petroleum.
• Polyester fibers are extremely strong, very durable, resistant to most chemicals and do not get wrinkled easily.
• Polyester does not absorb water, so it dries quickly.
• PET (Polyethylene terephthalate), the commonly used polyester, is made from two monomers by condensation polymerization.

• Polyester is used to make pants, shirts, suits and bed sheets either by itself or as a blend.
• Its water- resistant property makes it ideal for garments & jackets that are to be used in wet or damp environments.

Acrylic is a light weight soft and warm synthetic fabric which has a wool like feel.

• It does not shrink is wrinkle- resistant and cheaper than wool.
• It can also be dyed very well in a variety of color.

• Strong & warm, acrylic fiber is often used for making sweaters and tracksuits and as linings for boots and gloves as well as in furnishing fabrics and carpets.
• It is used in craft yarns, boat sails and vehicle covers.

Characteristics/ Advantages of synthetic fibers

1. They are stronger, more elastic and make tough and durable fabrics.
2. They are color- resistant and do not bleed color when washed.
3. They are easy to wash and dry.
4. They do not shrink when washed.
5. They are resistant to attack by moths.

Disadvantages of Synthetic fibers

1. Synthetic fibers cannot absorb moisture. This makes them unsuitable to be worn during summers when our body sweats.
2. It is dangerous to wear them while near fire, as they catch fire easily.
3. They cannot be easily ironed as they melt very easily.

Plastics

Properties & Uses of plastics

1. Plastic are poor conductors of heat and electricity. So they are used to make covering of electric wires and handles of tools.
2. Plastics are highly resistant to chemicals and water.
3. Plastics are lightweight, strong and durable and are therefore used to make parts for aircrafts, cars etc.

Problems with excessive use of plastics

1. Never throw plastic bags or other plastic articles into water bodies, drains or on roads.
2. Carry cotton or jute bags for shopping.
3. Buy products with less plastic packaging.
4. Recycling and reuse of plastics should be encouraging.

Summary

• Man-made fibers and not derived from natural sources are called synthetic fibers.
• The process of combining the monomers to form a polymer is called polymerization
• Nylon was the first synthetic fiber to be made entirely from chemicals.Basic raw materials for the production of nylon are coal, petroleum oil, water and air
• Polyester fibers are extremely strong, very durable, resistant to most chemicals and do not get wrinkled easily.
• Plastics are non- biodegradable and do not decompose for several years and When they are burnt, toxic fumes are released into the atmosphere causing pollution

• Notes
  • Synthethic Fibre and plastics Class 8 Notes
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  • synthetic fibres and plastics class 8 questions answers
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