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CBSE Class 8 Chemistry Notes for Chapter 1 Synthetic Fibres and Platsics

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       CHAPTER 1 SYNTHETIC FIBRES AND PLASTICS
 
SYNTHETIC FIBRES
The fibres which are not obtained from plants or animals and are made by humans are called synthetic or man-made fibres. Synthetic fibres are made from small units joined together. Such substances that are made up of a number of small units joined together are called polymers.
 
TYPES OF SYNTHETIC FIBRES
Rayon: By chemically treating wooden pulp, rayon can be obtained. Rayon is also called artificial silk as its properties are similar to silk. It can be mixed with cotton to make bed sheets and with wool to make carpets.
Nylon: Nylon was the first fully synthetic fibre and it was made from coal, air and water. It is very strong, elastic and light and is used to make articles such as ropes, tents, curtains. A nylon thread is stronger than a steel wire.
Polyester and acrylic: The fabrics made from polyester do not wrinkle easily and it is therefore becoming a popular choice for dress material. PET is a form of polyester that is used to make bottles, utensils, wires, etc. Acrylic fibre is used to make clothes that look like woollen clothes.
 
CHARACTERISTICS OF SYNTHETIC FIBRE

  • Dries quickly
  • Less expensive
  • Durable
  • Easy to maintain
  • Readily available
  • Melts when burned

 
PLASTICS
Plastic is also a polymer. Plastic can be shaped in any form and is therefore widely used to make objects like chairs, tables, toys, etc.
Plastics which bend easily on heating are known as thermoplastics. E.g. PVC, polythene, etc.
Plastics which cannot be softened by heating are called thermosetting plastics. E.g. Bakelite, melamine, etc.
 
CHARACTERISTICS OF PALSTIC

  • Non-reactive
  • Light, strong and durable
  • Poor conductors of heat and electricity

 
PLASTICS AND ENVIRONMENT
A substance which gets decomposed naturally is called biodegradable.
A substance which cannot be decomposed easily by natural processes is called non-biodegradable.
Plastic takes a very long time to degrade. Therefore, disposing of plastic substances are very difficult.
The 4 R principle helps in reducing the stress on the environment. These 4 R’s are: Reduce, Reuse, Recycle and Recycle.

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