Chemistry_Grade_10-12 (1).pdf

Pla can be used for products such as plant pots and

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PLA can be used for products such as plant pots and disposable nappies. It has been commercially available in some countries since 1990, and certain blends have proved successful in medical implants, sutures and drug delivery systems because they are able to dissolve away over time. However, because PLA is much more expensive than normal plastics, it has not become as popular as one would have hoped. Questions 1. In your own words, explain what is meant by a ’biodegradable plastic’. 2. Using your knowledge of chemical bonding, explain why some polymers are biodegradable and others are not. 3. Explain why lactic acid is a more useful monomer than starch, when making a biodegradable plastic. 4. If you were a consumer (shopper), would you choose to buy a biodegradable plastic rather than another? Explain your answer. 5. What do you think could be done to make biodegradable plastics more popular with consumers? 10.5.3 Plastics and the environment Although plastics have had a huge impact globally, there is also an environmental price that has to be paid for their use. The following are just some of the ways in which plastics can cause damage to the environment. 1. Waste disposal Plastics are not easily broken down by micro-organisms and therefore most are not easily biodegradeable. This leads to waste dispoal problems. 2. Air pollution When plastics burn, they can produce toxic gases such as carbon monoxide, hydrogen cyanide and hydrogen chloride (particularly from PVC and other plastics that contain chlorine and nitrogen). 3. Recycling It is very difficult to recycle plastics because each type of plastic has different properties and so different recycling methods may be needed for each plastic. However, attempts are being made to find ways of recycling plastics more effectively. Some plastics can be remelted and re-used, while others can be ground up and used as a filler. However, 195
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10.6 CHAPTER 10. ORGANIC MACROMOLECULES - GRADE 12 one of the problems with recycling plastics is that they have to be sorted according to plastic type . This process is difficult to do with machinery, and therefore needs a lot of labour. Alternatively, plastics should be re-used. In many countries, including South Africa, shoppers must now pay for plastic bags. This encourages people to collect and re-use the bags they already have. Activity :: Case Study : Plastic pollution in South Africa Read the following extract, taken from ’Planet Ark’ (September 2003), and then answer the questions that follow. South Africa launches a programme this week to exterminate its ”national flower” - the millions of used plastic bags that litter the landscape. Beginning on Friday, plastic shopping bags used in the country must be both thicker and more recyclable, a move officials hope will stop peo- ple from simply tossing them away. ”Government has targeted plastic bags because they are the most visible kind of waste,” said Phindile Mak- wakwa, spokeswoman for the Department of Environmental Affairs and Tourism. ”But this is mostly about changing people’s mindsets about the
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