Synthetic Fibres And Plastics class 8 | worksheet
Synthetic Fibres And Plastics. Download Synthetic Fibres And Plastics class 8 worksheet based on the latest CBSE syllabus including fill up, short and long questions.
Synthetic Fibres And Plastics class 8 (Points to remember)
Synthetic Fibres are human-made fibres made from polymers
Spandex is a synthetic fibre that was invented by Joseph Shivers in Virginia
Polymers: Are large molecules formed by the union of monomers
Thermosets: Type of plastics that cannot be remoulded once set.
What are Synthetic Fibres?
Synthetic fibres are made by human beings. That is why these are called synthetic or man-made fibres. 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.
Types of many repeating units.
1. Rayon: 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.
2. 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 fibre was strong, elastic and light. It was lustrous and easy to wash. So, it became very popular for making clothes. We use many articles made from nylon, such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains, etc.
3. 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.PET (polyethylene terephthalate) is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.
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.
Polythene (Poly+ethene) is an example of plastic. It is used for making commonly used polythene bags.
plastic which gets deformed easily on heating and can be bent easily are known as thermoplastics. Polythene and PVC are some of examples of thermoplastics. These are used for manufacturing toys, combs and various types of containers. On the other hand, there are some plastics which when moulded once, can not be softened by heating. These are called thermosetting plastics. Two examples are bakelite and melamine. Bakelite is a poor conductor of heat and electricity. It is used for making electrical switches, handles of various utensils, etc