Synthetic Fibers and Plastics

2.1 INTRODUCTION
The clothes which we wear are made of fabrics.
Fabrics are made from fibres obtained from natural or artificial sources.
Can you name some natural fibres ?
Fibres are also used for making a large variety of household articles. You have read in your previous classes that natural fibres like cotton, wool, silk, etc., are obtained from plants or animals. The synthetic fibres, on the other hand, are made by human beings.
That is why these are called synthetic or man-made fibres.
2.2 SYNTHETIC FIBRES

Synthesis means to make and synthetic means man-made.
So, man made fibres are called synthetic fibres. A synthetic fibre is also a chain of small units joined together. Each small unit is actually a chemical substance. Many such small units combine to form a large single unit called a polymer.
The word polymer comes from two Greek words; poly meaning many and mer meaning part/unit. So, a polymer is made of many repeating units.
A) Rayon
We have learnt that silk fibre obtained from silkworm was discovered in China and was kept as a closely guarded secret for a long time. Fabric obtained from silk fibre was very costly.
But its beautiful texture fascinated everybody. Attempts were made to make silk artificially.
Towards the end of the nineteenth century, scientists were successful in obtaining a fibre having properties similar to that of silk.
Fibre obtained by chemically treating wood pulp is called rayon or artificial silk.

Although rayon is obtained from a natural source, wood pulp, yet it is a man-made fibre.
Characteristics of rayon
• Cheaper than silk and can be woven like silk fibres.
• Highly absorbent, soft and comfortable. 
• Easy to dye in a wide range of colours, and drapes well.
Uses of rayon
• Widely used in all types of clothing and home furnishings.
• Mixed with cotton to make bed sheets and curtains, or with wool to make carpets.
B) Nylon
Nylon is another man-made fibre. In 1931, it was made without using any natural raw material (from plant or animal). It was prepared from coal, water and air. It was the first fully synthetic fibre. Nylon is a synthetic fibre made from coal, water and air.

Characteristics of nylon
Nylon is Strong, Elastic , Light, Lustrous , Easy to wash. So, it became very popular for making clothes.
Uses of nylon
We use Nylon to make Socks, Ropes, Tents, Toothbrushes, Car seat belts, Sleeping bags, Curtains, etc.
Point to note
Is nylon fibre really so strong that we can make nylon parachutes and ropes for rock climbing ?
Nylon is also used for making parachutes and ropes for rock climbing.
A nylon thread is actually stronger than a steel wire.

C) Polyester
Polyester is a synthetic fibre, derived from coal, air, water and petroleum. Polyester is made of repeating chemical units called esters.
Fabric made from polyester retains its shape and remains crisp. Polyester is easy to wash and dry.
Polycot is a mixture of polyester and cotton. Polywool is a mixture of polyester and wool. Terylene is a popular form of polyester, which can be drawn into very fine fibres. These fibres can be woven like any other yarn.
PET, or Poly-ethylene terephthalate, is another familiar form of polyester, which is used to make bottles, utensils, films and wires.
Polyester is also used for making hoses, ropes, nets, thread, raincoats, fleece jackets, clothing and medical textiles.

D) Acryclic
We wear sweaters and use shawls or blankets in the winter. Do you know the material with which they are made of ? Many of these are actually not made from natural wool, though they appear to resemble wool. These are prepared from another type of synthetic fibre called acrylic.
Acrylic is a synthetic polymer of methyl methacrylate.
Fabric made from acrylic is warm to wear, retains its shape and is durable. Acrylic is easy to wash and dries quickly. Acrylic is used in apparel like sweaters and socks, and in home furnishings such as furniture, carpets, blankets and upholstery fabrics. Industrial uses of acrylic include craft yarns, awnings, boat and vehicle covers, and luggage.

Point Of Safety
Synthetic fibres are more durable and affordable which makes them more popular than natural fibres. But they too have demerits. Synthetic fibres melt on heating. If the clothes catch fire, it can be disastrous. The fabric melts and sticks to the body of the person wearing it. We should, therefore, not wear synthetic clothes while working in in the kitchen or in a laboratory.
2.3 PLASTICS
You must be familiar with many articles used in our daily life like bottles, mugs, polythene bags, plastic chairs, clips, handles of kitchen wares, doctor’s gloves etc.
Have you ever thought with what material all these are made ?
All these are made of Plastics. Plastic is also a polymer like the synthetic fibre. All plastics do not have the same type of arrangement of units.
In some, the units are arranged in linearly as shown. Whereas in others, they are cross linked as shown.

Are all plastics of the same kind or are there different types of plastics, having different properties ?
Let’s see
Types of Plastics
Plastics can be broadly classified into two categories, depending on their interaction with heat.
A) Thermoplastics
Plastics which gets deformed easily on heating and can be bent easily are known as thermoplastics.
Polythene and PVC are some of the examples of thermoplastics. These are used for manufacturing toys, combs and various types of containers.
B) Thermosetting Plastics
Plastics which when moulded once, can not be softened by heating called thermosetting plastics. Bakelite and melamine are the examples. Bakelite is a poor conductor of heat and electricity.
It is used for making electrical switches, handles of various utensils, etc. Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics. It is used for making floor tiles, kitchenware and fabrics which resist fire.
Think it over !
Today if we think of storing a food item, water, milk, pickles, dry food, etc., plastic containers seem most convenient. Why is this so ?
This is because of their light weight, lower price, good strength and easy handling. Being lighter as compared to metals, plastics are used in cars, aircrafts and spacecrafts. The list is endless if we start counting articles like slippers, furniture and decoration pieces, etc.
Characteristic properties of Plastics
A) Plastic is non-reactive
You know that metals like iron get rusted when left exposed to moisture and air. But plastics do not react with water and air. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.
B) Plastic is light, strong and durable
As plastic is very light, strong, durable and can be moulded into different shapes and sizes, it is used for various purposes. Plastics are generally cheaper than metals. They are widely used in industry and for household articles.
C) Plastics are poor conductors
Plastics are poor conductors of heat and electricity. That is why electrical wires have plastic covering, and handles of screw drivers are made of plastic. As mentioned earlier, handles of frying pans are also made of plastic.
Do you Know
• Plastics find extensive use in the health-care industry. Some examples of their use are the packaging of tablets, threads used for stitching wounds, syringes, doctors’ gloves and a number of medical instruments.
• Special plastic cookware is used in microwave ovens for cooking food. In microwave ovens, the heat cooks the food but does not affect the plastic vessel.
• Teflon is a special plastic on which oil and water do not stick. It is used for nonstick coating on cookwares.
• Fire-proof plastics : Although synthetic fibre catches fire easily, it is interesting to know that the uniforms of firemen have coating of melamine plastic to make them flame resistant.
Plastics and the Environment
When we go to the market, we get usually things wrapped in plastic or packed in polythene bags. That is one reason why plastic waste keeps getting accumulated in our homes. Ultimately, plastic finds its way in the garbage. Disposal of plastic is a major problem. Why ?
A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. A material which is not easily decomposed by natural processes is termed as non-biodegradable.

Type of waste

Approximate time taken to degenerate

Nature of material

Peels of vegetable and fruits, leftover foodstuff

1 to 2 weeks.

Biodegradable

Paper

10–30 days

Biodegradable

Cotton cloth

2 to 5 mont hs

Biodegradable

Wood

10 to15 years

Biodegradable

Woollen clothes

About a year

Biodegradable

Tin, aluminium, and other metal cans

100 to 500 years

Non-biodegradable

Plastic bags

Several years

Non-biodegradable

Environmental Pollution By Plastics
Since plastic takes several years to decompose, it is not environment friendly. It causes environmental pollution. Besides, the burning process in the synthetic material is quite slow and it does not get completely burnt easily. In the process, it releases lots of poisonous fumes into the atmosphere causing air pollution.

Solving the problem
Avoid the use of plastics as far as possible. Make use of bags made of cotton or jute when you go for shopping. The biodegradable and non-biodegradable wastes should be collected separately and disposed off separately. It is better to recycle the plastic waste. Most of the thermoplastics can be recycled.
However, during recycling certain colouring agents are added.
This limits its usage especially for storage of food.
As a responsible citizen remember the 4R principle.

Also, develop the habits which are environment friendly.
Our Role in solving the problem
Have you ever seen a garbage dump where animals, especially cows, are eating garbage?
In the process of eating the food waste they swallow materials like polythene bags and wrappers of food.

Can you imagine the consequences ?
The plastic material chokes the respiratory system of these animals, or forms a lining in their stomachs and can be the cause of their death. The polybags carelessly thrown here and there are responsible for clogging the drains, too. Sometimes we are very careless and throw the wrappers of chips, biscuits and other eatables on the road or in parks or picnic places. Should we not think twice before doing so ?
As a responsible citizen what measures do you suggest to keep public places clean and free of plastic ?
FINAL MESSAGE
• Do not throw plastic bags in the water bodies or on the road.
• Take a cotton carry-bag or a jute bag while going for shopping.
• Try to minimise the use of plastic materials e.g., use a steel lunch box instead of a plastic one.
The amount of these resources in nature is limited. They can be exhausted by human activities.
Examples : Forests, Wildlife, Minerals, Coal, Petroleum, Natural gas, etc.

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