Concepts

  • Polymer :The long chain like molecule made from small molecules.
  • Natural Materials: which occurs in nature. Ex. wood, cotton , coal , graphite, diamond etc..
  • Man-made Materials: which made be chemical processes. Ex. plastics , paints , cement, fertilizers glass synthetic fibers..
  • Synthetic Fibers: Man-made material, thread-like. Ex.: Rayon , Nylon , Terylene.
    • Rayon:
      • A man-made fiber having silky texture ,Known as artificial silk , Made from cellulose obtained from wood pulp.
      • Used in textile industry for making fabrics , carpets , tyre cord , surgical dressings.
    • Nylon:
      • Made from simple chemicals obtained from coal.
      • First fully synthetic fibre.
      • Properties: very strong , elastic and lustrous , very thin fibre , do not absorb water , wrinkle resistant , fungus free.
    • Polyester:
      • Terylene , Decron , Terene are polyster fibres.Made from petroleum products.
      • Properties: quite strong , absorb very little water , wrinkle resistant
      • Used for making sarees, dresses. Ex. terylene with cotton gives terycot ,with wool it ives terywool.sail boats , water hoses.
  • Synthetic Plastics: can be easily mounded into any desired shape on heating. Ex.: Bakelite , Nylon , Terylene , PVC etc.
    • Plastics are two types:
      • Thermoplastics (can be softened on heating): long chain polymers with no cross linking , processed repeatedly. Ex.: Polythene , PVC , Nylon, Polyesters.
        • Polythene: Obtained from ethylene under high temp, high pressure and presence of a catalyst.
          • Properties: translucent material , light weight , flexible , insulator , do not absorb water.
          • Used for making sheets, packaging , water proofing etc.
        • PVC: Obtained by the polymerization of vinyl chloride. Used for making rain coats, handbags , shoe-sole etc.
        • Polystyrene: Obtained from the monomer styrene. highly transparent used for making hot drink cups, toys
        • Acrylic: highly transparent plastic resembling glass. soft , can be scratched. Dissolves in organic solvents.
        • Used for making lenses ,  aircraft window screws , making paints.
      • Thermosetting plastics ( can not be soften or melted ):no cross linking , can not be reprocessed.
        • Bakelite: Insulator , Once  set into  shape , does not melt/soften. Obtained by reacting phenol with formaldehyde. Used for making electrical switches and plugs , combs , pen bodies , photo frame etc..
        • Melamine: hard and high polish polymer. Used for making unbreakable dinner-ware and decorative.
  • Biodegradable substances :The substances which get decomposed to harmless substances through natural process are called biodegradable substances. For example: Kitchen waste , leftover food , paper , cotton cloth , Dry leaves.
  • Two fibers terylene with cotton gives terycot  , and with wool it gives terywool.

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