Man Made Organic Materials - Part IV

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Artificial rubber
Natural rubber is made out of latex from rubber trees. Synthetic or artificial rubber is made from by products of petroleum industry. There are two important types of synthetic rubber : neoprene and Thiokol. Artificial rubber has many properties, which are much better than natural rubber and therefore they find wide use in industrial and domestic applications.

Neoprene
Neoprene is made by polymerization of chloroprene or 2 chlorobutadiene. The equation below shows the reaction.  

(The IUPAC nomenclature of chloreprene is easy to understand. There are 4 carbon atoms. Hence the prefix to be used is “bute”. There are double bonds; thus the hydrocarbon is an alkene. There are two double bonds hence it is called buta-di-ene. Number the carbon atoms serially, so that the branch where the chlorine is attached comes at a lower number. Thus carbon atom number 2 and not 3 has the Cl atom attached to it. Thus the IUPAC name of this compound is 2 chloro – buta-di-ene.)

Properties of neoprene
1. Neoprene is non-inflammable. This property is opposite to that of natural rubber made from latex.
2. Neoprene is unreactive to many industrial chemicals such as oil, grease, petrol, other solvents.
    Natural rubber is reactive to all these chemical agents.
3. Neoprene does not change shape even at lower or higher temperatures. Thus neoprene can be used 
    over a wide range of temperatures.
4. Neoprene in principle is a thermoplastic rubber. It can re-used again and again.  

Uses of neoprene

  • Neoprene is used as an insulating material for electrical connections, especially where the environment has chemicals.

  • Neoprene is used to make conveyor belts, car belts, gaskets, etc.

  • Neoprene is used in petrol industry in the form flexible pipes or hoses. This is because neoprene is not attacked by petrol.  

Thiokol
Thiokol is made by polymerization of ethylene chloride with sodium polysulphide. Another name for ethylene chloride is 1,2-dichloroethane. The equation below shows the reaction. The reaction products are the polymer thiokol and sodium chloride.  

(The IUPAC nomenclature of ethylene chloride is easy to understand. There are 2 carbon atoms. Hence the prefix to be used is “eth”. There are no double bonds; thus the hydrocarbon is an alkane. Number the carbon atoms serially. The chlorine atoms are attached to the two carbon atoms. Hence dichloro name is used. Thus the IUPAC name of this compound is 1,2 dichloro – ethane.)

The properties and uses of thiokol are similar to neoprene.

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