Category Polymers

          Think of hospital equipment that is used for processes like sterilization. Any idea about the kind of polymers used in them as they need to withstand high temperature?

          Some polymers are stable at very high temperatures. These polymers have strong force of attraction between the molecules. They also have special network structure. Some additives are added to some of these polymers which enhance their thermal resistance.

          These polymers are usually known as high temperature polymers and can withstand a service temperature greater than 150 degrees. They can even withstand temperatures higher than 250 degrees for a short span. They are very expensive and hence are used in small amounts.

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          Polymers can be arranged in two formations. If the molecules do not have a long-range order, the polymer chain has an amorphous arrangement. Amorphous polymers are generally transparent.

          Contact lenses, plastic windows and transparent food wraps are generally made of amorphous polymers.

          What about polymers those are not transparent? Translucent and opaque polymers have crystalline arrangement of molecules. Here, the atoms and ions are arranged in definite patterns. Generally, the amount of light that can pass through a polymer decreases with increasing amounts of crystallinity. So, the opaqueness of a polymer is an indicator of the degree of crystallinity.

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                    Think of the human body. What is it that gives us our shape? The skeleton of course. Without the skeleton, we would be a lump of flesh. Similarly all polymers have a skeleton which gives them their structure. Organic polymers have a carbon backbone. Their monomers are simple organic compounds.

           On the other hand, the backbone of an inorganic polymer is constituted by elements other than carbon, say phosphorous or sulphur. Most of the organic polymers have simple structures while inorganic polymers are highly branched with complex structures.

           Though they have carbon bonding, graphite and diamond are inorganic polymers. This is because they are constituted by carbon atoms alone which crosslink to give their structure.

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           Nylon is a synthetic fibre which is commonly used in the textile industry. The word fibre will give you an image of interlinked threads. Synthetic fibres are man-made fibres that are derived from several chemical processes. They can be easily woven because of their thread-like nature. The force of attraction between the monomers of a fibre is very strong; the monomers crosslink to form a strong hydrogen bond.

          Nylon is also used for making fishing nets, ropes and parachutes because it is strong and long lasting. Like nylon, polyester and rayon too are synthetic fibres. They are non-toxic substances and can be dyed.

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          Unlike thermoplastics, thermosetting plastics cannot be remoulded or reshaped. It assumes a permanent hard shape once heated.

          Initially, this is a liquid or a soft solid. Chemical reactions take place when it is heated and the long polymer chains crosslink to form a three dimensional structure. You might have bright coloured melamine dinnerware at home.  Melamine is a thermosetting plastic. Bakelite, which is used for insulating electric wires, also belongs to this category.

          Thermoplastics can be remelted quickly, but thermosetting plastics can withstand high temperatures. It cannot be recycled for the same reason.

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           Do you know how a plastic bottle is made? At first, the raw material used for making the bottle is heated and blown. It is then passed through another mould which gives it shape.

          The production of a plastic bottle is possible because the raw material can be moulded into any shape at a certain temperature. It then solidifies after cooling. Polymers of this kind are known as thermoplastics. Thermoplastics soften up on heating and harden when they are allowed to cool down They can be melted and recast into any possible shape. PET bottles and toys are has usually made of thermoplastics.

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