A5 Polymers
1. Plastics find many uses in modern society. i. Suggest one named plastic that is widely used to manufacture containers for liquids. Explain why its properties make it particularly useful for manufacturing containers. ii. Suggest one named plastic that is widely used to manufacture electrical fittings like plugs and sockets. Explain why its properties make it particularly useful for manufacturing these fittings.
2. PVC (polychloroethene) is an important plastic and is used to insulate electrical cables. However PVC is not particularly flexible. State and explain how the properties of PVC are changed to make it more flexible and suitable for insulating electrical cables.
3. Polypropene is a useful plastic particularly good for making tough bottles, ropes and crates. Explain, in terms of atom economy, why the manufacture of polypropene could be considered to be an example of “green chemistry”.
4. i. Explain briefly the difference between a thermosetting polymer and a thermoplastic polymer. ii. What is the main problem when making an object using a thermosetting plastic? iii. Suggest which type of polymer is most suitable for making the following articles and give a brief reason for your choice: a. a plastic bottle for containing an acid b. a water pipe, to drain water from a washbasin c. the casing for an electrical plug
5. Polythene (polyethene) is the most commonly used plastic. It is available in both low density (LDPE) and high density (HDPE) forms. i. In addition to their density differences, what is the main difference between the physical properties of LDPE and HDPE? ii. Explain the reason for the physical property difference referred to in part iii.
6. i. Draw a section of the polymer formed by 2-methylpropene, include at least three monomer units in your diagram. ii. Identify and explain how the physical properties of the polymer formed by 2-methylpropene is different to the polyethene. iii. 2-methylpropane can form an atactic or isotactic polymer. Explain with the use of diagrams the difference in structure between atactic and isotactic polymers.
7. Rubber is a natural polymer known as an elastomer. i. State and explain whether an elastomer is a thermosetting or thermoplastic. ii. What structural features of the polymer chains in an elastomer give it the characteristic “elastic” property?
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