RAYON

RAYON

You have read in Class VII 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. Such a fibre was obtained by chemical treatment of wood pulp. This fibre was called rayon or artificial silk. Although rayon is obtained from a natural source, wood pulp, yet it is a man-made fibre. It is cheaper than silk and can be woven like silk fibres. It can also be dyed in a wide variety of colours. Rayon is mixed with cotton to make bed sheets or mixed with wool to make carpets. (Fig. 3.2.)

Figure 3.2: Articles made of rayon

Source: This topic is taken from NCERT TEXTBOOK

NYLON

NYLON

Nylon is another man-made fibre. In 1931, it was made without using any natural raw material (from plants or animals). It was prepared from coal, water and air. It was the first fully synthetic fibre.

Nylon fibre was strong, elastic and light. It was lustrous and easy to wash. So, it became very popular for making clothes.

Figure 3.3: Various articles made from nylon

We use many articles made from nylon, such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains, etc. (Fig. 3.3). Nylon is also used for making parachutes and ropes for rock climbing (Fig. 3.4). A nylon thread is actually stronger than a steel wire.

Figure 3.4: Use of nylon Fibres

Let us find out.

Activity 9.1:   ( fibres of different strength )

Take an iron stand with a clamp. Take a cotton thread of about 60 cm in length. Tie it to the clamp so that it hangs freely from it as shown in Fig. 3.5. At the free end suspend a pan so that weight can be placed in it. Add weight one by one till the thread breaks. Note down the total weight required to break the thread. This weight indicates the strength of the fibre. Repeat the same activity with threads of wool, polyester, silk and nylon. Tabulate the data as shown in Table 3.2. Arrange the threads in order of their increasing strength.

Figure 3.5: An iron stand with a thread hanging from the clamp

Table 3.2:

You may use a hook or a nail on the wall for hanging the fibres and a polythene bag at the other end. In place of weights, you may use marbles (or pebbles) of similar size.

(Precaution: Note that all threads should be of the same length and almost of the same thickness.)

Source: This topic is taken from NCERT TEXTBOOK

POLYESTER AND ACRYLIC

POLYESTER AND ACRYLIC

Polyester is another synthetic fibre. Fabric made from this fibre does not get wrinkled easily. It remains crisp and is easy to wash. So, it is quite suitable for making dress material. You must have seen people wearing polyester shirts and other dresses. Terylene is a popular polyester. It can be drawn into very fine 

fibres that can be woven like any other yarn.

Polyester (Poly+ester) is actually made up of the repeating units of a chemical called an ester. Esters are the chemicals which give fruits their smell. Fabrics are sold by names like polycot, polywool, terrycot, etc. As the name suggests, these are made by mixing two types of fibres. Polycot is a mixture of polyester and cotton. Polywool is a mixture of polyester and wool.

PET (polyethylene terephthalate) is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

Look around and make a list of things made of polyester.

We wear sweaters and use shawls or blankets in the winter. 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. The wool obtained from natural sources is quite expensive, whereas clothes made from acrylic are relatively cheap. They are available in a variety of colours. Synthetic fibres are more durable and affordable which makes them more popular than natural fibres.

You have already performed an activity of burning natural and synthetic fibres (Activity 3.6 of Class VII*). What did you observe? When you burn synthetic fibres you find that their behaviour is different from that of the natural fibres. You must have noticed that synthetic fibres melt on heating. This is actually a disadvantage of synthetic fibres. 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.

All the synthetic fibres are prepared by a number of processes using raw materials of petroleum origin, called petrochemicals.

Note:

* Activity 3.6 (from 7^th class):

Take an artificial (synthetic) silk thread and a pure silk thread. Burn these threads carefully. Did you notice any difference in the smell while burning? Now, burn a woollen fibre carefully. Did it smell like burning of artificial silk or that of pure silk? Can you explain why?

Source: This topic is taken from NCERT TEXTBOOK