Synthetic Fibres , Plastics | its classification | how to prepare fibres?

  -  Synthetic Fibres & Plastics

 Fabrics 

     Fabrics are made from fibres. A fibre is a very thin, thread like strand. Fibres may be made from Natural or Artificial Sources. 

 Natural Fibres

       The fibre which is obtained from plants and animals anre called Naturals fibres. Like cotton, silk, wool, etc. 

Synthetic Fibres

       The artificial fibre are made by human beings and so are also called synthetic false. Synthetic fibre is a chain of small units of chemical compounds joined together. 

Monomers 

       A chemical substance having a single unit structure is called a monomer. A monomer may be thought of a small molecule. 

Polymers

     Many monomers combine to form a large unit called a polymer. The process of joining together of monomers to form a polymer is called polymerisation. A polymer a big molecule formed by the combination of a large number of small molecules. 

Polymer may be synthetic natural or synthetic :- cotton, wool, and silk are natural polymers. Cotton is a polymer of glucose. Wool and silk are polymers of amino- acids (that is protein).

 

Depending upon the types of chemicals used for making synthetic fibres. We have five major types of synthetic fibres. 

        1- Rayon

        2- Nylon

        3- Polyester

        4- Acrylic

        5- Lycra or Spandex

Rayon :- it is also known as synthetic silk because it's silk appearance is prepared from cellulose by subjecting it to extensive chemical treatment. Cellulose is obtained from cotton, wood and other plant products. Rayon is cheaper to make because it's preparation uses waste cotton paper. Rayon has the advantage that it can be blended with others fibres like wool and cotton. 

 Nylon :- It is made without using any natural raw material (plant or animal). It is made from coal and water. Nylon is useful as fibre as sheet and as moulded solids and is used in making a number of products like sarees, thread, ropes, fishing nets, carpets, upholstery, umbrella covers and parachutes, etc. 

Polyester :- Alcohal and organic acids react together to form compounds which are called esters. They give fruit like smell. Polyester is a type of polymer made up  of the repeating units of ester. Depending upon the types of alcohols and acids used, we have, different varieties for polyester. 

 Terelyne, Decron, Terene and polyester are all different brands of polyester. 

 Polyester is blended with cotton and wool in different ratio to obtain 'Polycot' or terrycot, polywool or terrywool. 

Acrylic :- It is made from a chemical 'Acrylonitrile' by the process of the polymerisation and due to it's wool like feel, is greatly used as a substitute for wool for making winter wears, shawls and blankets, etc. Acrylic absorbs very little water and so a thing made of acrylic dries very quickly. Acrylic fibre is resistant to moths And most chemicals. A form of acrylic plastic is transparent and is used as transparent 'sheersh and as a covering over automobile lights, lenses, surgical tools etc. 

Lycra or Spandex

      It is greatly elastic and is able to stretch about 600 times with the ability to return to it's original shape. It is used in combination with cotton in making garments like swim suits, T-shirt and universal- size caps. 

Plastics :- 

   Like synthetic fibres, plastic are also polymers. Depending upon the chemical used in making plastic, there is a great variety of plastics. 

  There are two main groups of plastics. 

          1- Thermosets

          2- Thermoplastic

 Thermosets :- Plastic which when moulded ones, cannot be softened by heating are called thermosetting. For example, Bakelite and Melamine. 

Bakelite :- Bakelite being a poor conductor of electricity and also heat resistant is used for making electrical switches, handles of utensils, part of fibre glass sheet used for making helmets, etc. 

Melamine :- Melamine is used in making good quality table wares and as a coating on uniforms of fire fighting personal to make them fine- resistant. 

 Thermoplastics :- Plastics which get deformed easily on heating and can be bent easily are known as thermoplastics. Thermoplastics can be drawn into fine fibres and can be moulded to any desired shape or stretched and spread as sheets. The moulded  plastics used in making articles like carpets, mugs, containers, etc,. Some of the thermoplastics in use are:

   (i) Polythene :- It is a type of plastic used for making commonly used polythene bags. 

   (ii) Teflon (Poly-tetra-flouroethylene(PTFE) :-  It is a non- stick plastic used as a non stick coating in Cookwares. It is very tough and insulating cables wires etc. 

    (iii) PVC (polyvinyl chloride) :- Commonly used for making plumbing materials, furniture, doors, bath rooms containers and insulating cables wires, etc. 

    (iv) PS (polystyrene) :- On mixing with synthetic rubber it is used in lining refrigerator. Air bubbled polystyrene is used as insulators (thermocol) boxes for storing ice or for packaging gadgets. 

     (v) PET ( Poly- Ethylene Terephthalate) :- It is a very light weight, naturally colourless, transparent, strong and impact resistant. It is increasingly glass to make bottles, jars and utensils. 

 

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