Chemistry_Grade_10-12 (1).pdf

After the war synthetic rubber also played an

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tyres and parts of war machinery. After the war, synthetic rubber also played an important part in the space race and nuclear arms race. Polyethene/polyethylene (PE) Polyethylene (figure 10.1) was discovered in 1933. It is a cheap, flexible and durable plastic and is used to make films and packaging materials, containers and car fittings. One of the most well known polyethylene products is ’Tupperware’, the sealable food containers designed by Earl Tupper and promoted through a network of housewives! Polytetrafluoroethylene (PTFE) Polytetrafluoroethylene (figure 10.9) is more commonly known as ’Teflon’ and is most well known for its use in non-stick frying pans. Teflon is also used to make the breathable fabric Gore-Tex. C C F F F F C C F F F F n Figure 10.9: A tetra fluoroethylene monomer and polytetrafluoroethylene polymer Table 10.1 summarises the formulae, properties and uses of some of the most common plastics. Table 10.1: A summary of the formulae, properties and uses of some common plastics Name Formula Monomer Properties Uses Polyethene (low den- sity) -(CH 2 -CH 2 ) n - CH 2 =CH 2 soft, waxy solid film wrap and plastic bags Polyethene (high den- sity) -(CH 2 -CH 2 ) n - CH 2 =CH 2 rigid electrical insulation, bottles and toys Polypropene -[CH 2 -CH(CH 3 )] n - CH 2 =CHCH 3 different grades: some are soft and others hard carpets and uphol- stery Polyvinylchloride (PVC) -(CH 2 -CHCl) n - CH 2 =CHCl strong, rigid pipes, flooring Polystyrene -[CH 2 -CH(C 6 H 5 )] n CH 2 =CHC 6 H 5 hard, rigid toys, packaging Polytetrafluoroethylene -(CF 2 -CF 2 ) n - CF 2 =CF 2 resistant, smooth, solid non-stick surfaces, electrical insulation Exercise: Plastics 1. It is possible for macromolecules to be composed of more than one type of repeating monomer. The resulting polymer is called a copolymer . Varying the monomers that combine to form a polymer, is one way of controlling the properties of the resulting material. Refer to the table below which shows a number of different copolymers of rubber, and answer the questions that follow: 193
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10.5 CHAPTER 10. ORGANIC MACROMOLECULES - GRADE 12 Monomer A Monomer B Copolymer Uses H 2 C=CHCl H 2 C=CCl 2 Saran films and fi- bres H 2 C=CHC 6 H 5 H 2 C=C-CH=CH 2 SBR (styrene butadiene rubber) tyres H 2 C=CHCN H 2 C=C-CH=CH 2 Nitrile rubber adhesives and hoses H 2 C=C(CH 3 ) 2 H 2 C=C-CH=CH 2 Butyl rubber inner tubes F 2 C=CF(CF 3 ) H 2 C=CHF Viton gaskets (a) Give the structural formula for each of the monomers of nitrile rubber. (b) Give the structural formula of the copolymer viton. (c) In what ways would you expect the properties of SBR to be different from nitrile rubber? (d) Suggest a reason why the properties of these polymers are different. 2. In your home, find as many examples of different types of plastics that you can. Bring them to school and show them to your group. Together, use your examples to complete the following table: Object Type of plastic Properties Uses 10.5.2 Thermoplastics and thermosetting plastics A thermoplastic is a plastic that can be melted to a liquid when it is heated and freezes to a brittle, glassy state when it is cooled enough. These properties of thermoplastics are mostly
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