Can someone give me notes for Synthetic fibres class 8th
Answers
II. A Synthetic Fibre is a chain of small units of chemical substance joined together. Many such single units combine to form single unit called Polymer. Polymer means �made of many units joined together�.
III. Types of Synthetic Fibre
 Rayon- Rayon is synthesized from wood pulp. Rayon resembles silk, so it is also known as artificial silk. Rayon can be dyed in different colours and is much cheaper than silk.
 Nylon- Nylon was first commercially synthesized fibre. Nylon is synthesized from coal, water and air. Nylon is very strong and its fabric is like silk.
 Polyester- Polyester, one of the most popular man-made fibres. It is made of repeating unit of a chemical called ester. It is widely used to make clothes.
 Acrylic- Acrylic is a man-made fibre. Acrylic is known as artificial wool or synthetic wool because it resembles wool. Acrylic is cheaper than natural wool and can be dyed in various colour. This makes acrylic is very popular among other fabrics.
IV. Characteristics of Synthetic Fibres
 Synthetic fibres are cheaper than natural fibre.
 Synthetic fibres are stronger than natural fibre.
 Synthetic fibres are more durable than natural fibre.
 Synthetic fabrics are dried up in less time.
 Synthetic fibres are easy to maintain and wash.
V. Plastics
Plastic is a polymer that can be recycled, coloured, reused, mould or drawn into wires or various other shapes. Units of some plastics have linear arrangement while some plastics are formed by the cross linked arrangement of their units. Thus, plastic is used in making toys, suitcase, bags, cabinets, brush, chairs, tables, and many other countless items. Polythene is one of the most famous types of plastic, which is used in manufacturing of carry bags.
Types of Plastics
1. Thermoplastic: Plastics which can be easily bent or deform on heating are known as thermoplastic. PVC and Polythene are the examples of thermoplastics.
2. Thermosetting plastic: Plastics which do not get deformed or softened on heating when mold once, are called thermosetting plastics. Bakelite and melamine are the examples of thermosetting plastics.
Characteristics’ of Plastics
 Plastic is a poor conductor of heat and electricity.
 Plastic does not react with air and water and with many of the chemicals.
 Plastics are light weight, durable, cheap and very strong.
 Plastics are non- biodegradable substances. It takes many years to get decomposed and sometimes does not get decomposed at all. Thus plastic is not environment friendly.
 Plastic does not rust.
Explanation:
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.
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.
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.
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.
Synthetic Fibres and Plastics 1
Natural Fiber
The naturally occurring fibres that humans derive from plants or animals are known as natural fibres. Eg: cotton, wool, silk, etc.
Synthetic Fibres and Plastics 2
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.
Synthetic Fibres and Plastics 3
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.
Synthetic Fibres and Plastics 4
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.
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.
Synthetic Fibres and Plastics 5
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.
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
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
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.
Synthetic Fibres and Plastics 6
Implement the 4 R principle in everyday life. Following are the 4Rs:
Reduce
Reuse
Recycle
Recover
These habits are environment-friendly.
Hope it helps
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