CBSE Class 8 Science Chapter 3 Notes: Synthetic Fibres And Plastics

 

CBSE Class 8 Science Chapter 3 Notes: Synthetic Fibres And Plastics

Clothes that we wear on a daily basis are made of fabrics. Fabrics are made of fibres which are obtained from natural and artificial sources. Wool, silk, and cotton are a few examples of natural fibres and fibres like polyesters and terylene are a few examples of synthetic fibres. In class 8 science chapter 3, the various types of synthetic fibres along with their characteristics are mentioned.

Let’s Build

Fibre

• The clothes, which we wear are made of fabrics.
• Fabrics are made from fibres obtained from natural or artificial sources.
• Fibres are also used for making a large variety of household articles.

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Polymer

• The word ‘polymer’ comes from two Greek words; poly meaning many and mer meaning part/unit.
• A polymer is a substance composed of many repeated similar subunits.

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Synthetic Fibre

• Fibres that are made or created by humans are known as synthetic or man-made fibres.
• Humans have been able to make a variety of synthetic fibres. Eg: rayon, nylon etc.

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Natural Fibre

The naturally occurring fibres that humans derive from plants or animals are known as natural fibres. Eg: cotton, wool, silk, etc.

The Story of the Silkworm

Silk

• Silk fibre is obtained from the cocoon of a silkworm. It takes 10 kg of the cocoon material to create 1kg of silk.
• The process was discovered in China where it was kept as a closely guarded secret for a long time.
• Silk is costly due to the material quality and production process involved. It is used in making sarees, ties, etc.

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Raving about Rayon

Rayon

• Rayon is made from purified cellulose, which is chemically converted into a soluble compound.
• Rayon comes from natural sources such as wood pulp but is considered as a man-made fiber. This is because rayon can be treated chemically.
• When rayon is compared with silk, it is inexpensive but can be woven like silk fibres.

Nylon

• Nylon is a synthetic fibre obtained from coal, water and air.
• The first fully synthetic fibre obtained was nylon.
• The characteristic properties are that it is light, strong, and elastic.
• Nylon finds application in the manufacturing of socks, ropes, tents, car seat belts, sleeping bags, curtains etc.

To know more about Rayon and Nylon, visit here.

Pushy – Pull Polyesters

Polyester

• Polyester is made of repeating units of a chemical called an ester.
• It is a crease free synthetic fibre.
• It is best suited for the making of dress materials as it is crisp and is easy to wash.
• A popular polyester is Terylene.

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Fake Sheep – Acrylic

Acrylic Fibre

• Acrylic is a synthetic fibre that resembles wool.
• The wool obtained from natural sources is quite expensive, whereas clothes made from acrylic are relatively cheap.
• Synthetic fibres are more durable and affordable which makes them more popular than natural fibres.

Plastic Attack Alert

Plastic

• Plastic is also a polymer like the synthetic fibre.
• All plastics do not have the same type of arrangement of units. In some, it is linear whereas in others it is cross-linked.
• Plastic can be recycled, reused, coloured, melted, rolled into sheets or made into wires. That is why it finds such a variety of uses.

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Thermoplastics

Plastic, which gets deformed easily on heating and can be bent easily are known as thermoplastics. Eg: polythene and PVC

Thermosetting Plastics

Plastics, which when moulded once, can not be softened by heating. Eg: bakelite and melamine.

Characteristics of Plastics

– Plastic is non-reactive
– Plastic is light, strong and durable
– Plastic is a poor conductor

To know more about Properties of Plastics, visit here.

Biodegradable and Non-Biodegradable Materials

A material that decomposes through natural process is biodegradable and materials that are not easily decomposed by natural processes is termed as non-biodegradable.
Eg: Biodegradable – fruits, paper
Non Biodegradable – plastic, tin

To know more about Biodegradable and Non-Biodegradable Materials, visit here.

Environmental Effects on Plastic

• Plastic takes several years to decompose, it is not environmental friendly.
• It causes pollution.
• The burning process in the synthetic material is quite slow and it does not get completely burnt easily.
• It releases lots of poisonous fumes into the atmosphere causing air pollution in the process.

To know more about Effects of Plastics, Know more

Implement the 4 R principle in everyday life. Following are the 4Rs:

• Reduce
• Reuse
• Recycle
• Recover

These habits are environment-friendly.