synthetic fibers and plastics class 8, NCERT - easy study material-notes- important topic

SYNTHETIC FIBERS AND PLASTICS- IMPORTANT TOPICS

synthetic fibers and plastics class 8

plastic bottles in nylon net

In our daily life, we are using different types of fabrics which are made up of natural and synthetic fibers. Natural fibers like cotton and wool are obtained from plants and animals. 

Synthetic fibers are made by human beings and hence they are called man-made fibers.

Synthetic fibers are made by the process of polymerization. Greek words 'poly' means many and 'mer' means unit or part. 

So a polymer is made of many repeating units joined together. Each repeating unit is called a monomer. The polymer is similar to a chain of beads.

Example: in polyester, an ester is a repeating unit. Cellulose is a natural polymer with many glucose units.

beads on chain

CHARACTERISTICS OF SYNTHETIC FIBRES

Fabrics made up of synthetic fibers are very popular. They are durable, less expensive, and can be easily maintained. They dry up quickly and are wrinkle-free. The color of synthetic fabrics will not fade.

TYPES OF SYNTHETIC FIBRES

                                        RAYON

• Rayon is a synthetic fiber having properties similar to that of silk. Hence it is called artificial silk.
• On the chemical treatment of wood pulp, we can obtain a rayon.
• It is cheaper than silk and can be dyed in a variety of colors.
• When rayon is mixed with cotton, we can make bed sheets.
• When it is mixed with wool, we can make carpets.

rayon mat

NYLON

Nylon is prepared from coal, water, and air. Nylon fibers are elastic, strong, and light. It is lustrous and can be washed easily. It dries up fast.

 So it is popular in making clothes, socks, tents, toothbrush bristles, seat belts, curtains, etc. Since it is strong and durable, it is widely used for making rock climbing ropes and parachutes.

parachute nylon

nylon rope

nylon socks

toothbrush bristles nylon

POLYESTER

Polyester is made up of repeating units of ester. Terylene and Polyethylene terephthalate(PET) are very familiar polyesters used by us. 

Terylene can be woven like any other yarn. It does not get wrinkled easily and is easy to wash. Polycot, poly-wool, and terry cot are some of the fabrics made by mixing with cotton and wool.

poly cot- polyester+cotton

poly wool-polyester+wool

polyester shirt

PET is used for making bottles, utensils, wires, films. and many other products.

PET container

ACRYLIC

Acrylic is another synthetic fiber that resembles natural wool. Clothes made from acrylic are less expensive and are durable. It is available in different colors. We are using sweaters, shawls, blankets and soft toys made up of acrylic fibers.

Acrylic toy

acrylic blanket

BURNING TEST OF FIBRES

When you burn a synthetic fiber, it melts. But on burning a natural fiber like cotton, it forms ash. If synthetic clothes catch fire, it can be disastrous as it melts and sticks to the body. So it is not advisable to wear synthetic clothes in the kitchen and laboratory.

PLASTICS

Plastics are also polymers in which the repeating units are arranged in the linear or cross-linked pattern. The main advantage of plastic is that it can be recycled and reused. It can be remolded into different shapes and colors.

Plastics can be classified into two.

Thermoplastics and Thermosetting plastics

THERMOPLASTICS

Plastic which gets deformed on heating and can be bent easily are known as thermoplastics. It can be reused and recycled.

Example: Polythene and PVC

They are used for manufacturing toys, pipes, combs, and containers.

PVC toy

PVC pipe

 

THERMOSETTING PLASTICS

Plastic which when molded once, can not be softened on heating is called thermosetting plastic. This kind of plastic will get hardened on heating. Hence it can not be recycled or reused.

Example- Bakelite and Melamine

old phone bakelite

switches bakelite

melamine utensils

Bakelite is used for making handles of kitchen utensils and electrical switches as it is a poor conductor of heat and electricity.

Melamine is used for making kitchenware, floor tiles, and fire-resistant fabrics. It can resist heat better than other kinds of plastics.

CHARACTERISTIC PROPERTIES OF PLASTICS

1. Plastics are non-reactive- plastics do not react with air or water and are not corroded easily.

2. Plastics are strong, durable, and light- since they have these properties, they can be molded into various shapes and sizes.

3. Plastics are poor conductors of heat and electricity- since they have these properties, it is widely used as a covering for electrical wires and handles of testers and screwdrivers. Handles of kitchen wares are made up of thermosetting plastics as it is a poor conductor of heat.

PLASTICS AND THE ENVIRONMENT

Plastic causes environmental pollution if it is not disposed of properly. It is a threat to earth as it causes soil pollution, air pollution, and water pollution.

Avoid the use of one-time-use plastics as far as possible. Plastic waste should be collected and given to recycling. Do not litter public places. Use paper bags, cloth bags, and jute bags.

BIODEGRADABLE - materials that get decomposed easily by natural processes.

example; paper, wood, vegetable waste

NON-BIODEGRADABLE-materials which is not easily getting decomposed by natural processes

example: plastics

We have discussed the importance of synthetic fibers and their major uses. I have tried to give some insight into the different types of polymers used in our daily life.

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