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Saturday, February 25, 2012

Exam Ready Notes SYNTHETIC FIBRES AND PLASTICS

  1. 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 ‘polymercomes from two Greek words; poly meaning many and mer meaning part/unit. So, a polymer is made of many repeating units.
  2. Polymers occur in nature also. Cotton, for example, is a polymer called cellulose.  Cellulose is made up of a large number of glucose units
  3. Rayon : 
  4. 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.
  5. 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
  6. Terylene is a popular polyester. It can be drawn into very fine fibres that can be woven like any other yarn.  
  7. PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.  
  8.  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.
  9.  All the synthetic fibres are prepared by a number of processes using raw materials of petroleum origin, called petrochemicals.
  10.   Polythene (Poly+ethene) is an example of a plastic. It is used for making commonly used polythene bags.
  11. Plastic is also a polymer like the synthetic fibre. All plastics do not have the same type of arrangement of units. In some it is linear, whereas in others it is cross-linked.
  12. . Plastic can be recycled, reused, coloured, melted, rolled into sheets or made into wires.
  13.  plastic 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.
  14. 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. 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 
  15. Plastics  as Materials  of   Choice
    • Plastic is non-reactive
    • Plastic is light, strong and durable
    • Plastics are poor conductors
    • 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, doctorsgloves 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.

  16. asa

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