Polythene was the first of the polymers to be discovered. Polyethene is a polymer produced by reacting oxygen and ethene, in this reaction the small ethene molecules attach together to form long chain polymer molecules. This process is known as addition polymerisation. Melamine is an organic base molecule. It contains 66% Nitrogen by mass and, if mixed with resins, has fire retardant properties due to its release of nitrogen gas when burned or charred.
Thermoplastics can stretch or bend whereas thermosetting is rigid and breaks when bent. Thermoplastic softens and melts when heated whereas thermosetting chars and decomposes. Thermoplastic can be moulded into new shapes whereas thermosetting cannot be remoulded into new shapes once set.
The molecules in thermoplastic are often tangled around each other which make the polymer flexible. There are also weak forces of attraction between the molecules. When the thermoplastic polymer is heated up, these forces are broken and the molecules slide past each other. This allows the polymer to be remoulded.
When a thermosetting polymer is made, covalent bonds form between the molecules. These cross links are very strong and stop the molecules moving past each other. This is why the polymer is rigid and cannot be remoulded. If the thermosetting polymer is heated up, it does not melt, it just chars.
There are a lot of varieties of plastics available to the public. Some of these plastics are:
- Polyethylene terephthalate- Water bottles and fizzy drinks bottles
- High density polyethylene- Detergent bottles, milk bottles, yoghurt and margarine tubs
- Polyvinyl chloride- Cling film and vegetable oil bottles
- Low density polyethylene- Bin liner bags and squeezable bottles such as mustard or honey bottles
- Polypropylene- Ketchup bottles and medicine bottles
- Polystyrene- Grocery store meat trays and egg cartons
- Tupperware
Plastics are very useful items and can be used for a variety of different things. They can be used for:
As you can see the world has a very mixed usage of plastics. Plastics are used in a wide range of applications, and some plastics items, such as food packaging, become waste only a short time after purchase. Plastics are used the primarily for packaging because they are lightweight and durable. This means that they will not add to the cost of food items when they are being shipped. This is because they do not add much weight to the product.
Plastics are used secondarily for building and construction, such as guttering, because they are tough, durable and water resistant. In addition, most polymer chains may have branches on them and this affects the strength of the polymer. For example High density polyethene has few polymer branches whereas Low Density polyethene has many polymer branches; this will result in HDPE being much stronger than LDPE. Therefore HDPE would be used for such a job because it is much less stretchy than other plastics and much stronger. In addition HDPE can also be used in temperatures up to 120®C which means that it is very durable. Moreover by adding polymers such as unplasticised PVC, this is a hard polymer, to plastics it will increase the strength of that plastic therefore making it more tough and more durable.
Plastics are used thirdly as electrical devices because they insulated against electricity. Items such as earth wire are made from a plastic called fibrous plastic because it is a cheap, tough and a very insulating plastic. On the other hand, some plastic items lend themselves to be reused many times over. Reusing plastic is preferable to recycling as it uses less energy and fewer resources. Long life plastics used in packaging has become more widespread in recent years, replacing less durable alternatives, therefore reducing waste.
The evidence above supports Alan and Susie because it shows that plastics are not biodegradable as they are used for building and construction as guttering. It supports Alan also though because it shows that they are cheap as they are used for packaging however that also proves that they are tough and durable.
Advantages of plastics
Plastics are very useful because they can be used for many different situations. They are useful as they have many different properties. These properties include being recyclable (thermoplastic) and biodegradable. Biodegradable means that the plastic is capable of decaying through the use of living microorganisms, therefore if all plastic bags were biodegradable then landfill would not be as much of a problem. This is because once the plastic has biodegraded, the remains will be returned to the soil and fertilise it.
Plastics can be very versatile materials. This means they are able to adapt. If they are thermoplastic then they would possess this property, this could that they could in fact be used instead of other materials. For example, using plastic instead of metal. One primary advantage of using plastic over metal is weight reduction. Reducing product weight with plastics gives you more parts per pound of metal, significantly reduces shipping costs and improves the ease of utilisation for the user. In addition, if you were to choose plastic over metal for building a strong house then in would in fact benefit you. This is because you can get products which are lightweight, easier to use and possess more structural strength. Plastic parts can be made stronger than metal via engineering.
Reusing plastic is preferable to recycling as the recycling process uses big amount energy resources; however recycling is still better than littering it.
Recycling plastics can have a significant contribution to the environment. This is because:
- Reduces energy consumption by two thirds
- Reduces water usage by 90%
- Reduces carbon dioxide emissions by two and a half times
Council recycling bins (green, brown and glass) are our local recycling scheme; however other schemes include recycling plants and recycling in school. These are a great way for you to involve yourself and help the environment. In addition there are also some national recycling schemes available to get yourself involved in.
Waste cycle is a nationwide campaign that operates a recycling service providing waste solutions nationally. They arrange collection of your waste anywhere in the UK using local waste management companies, who help with service and vehicles. Waste cycle is keen to help you decrease waste and seperate different waste materials through the use of many skips, bins or containers. Their service is designed to reduce your total waste costs by offering a recycling option where it is economically and environmentally beneficial. You will be provided with the best service, which may lead disposal at other licensed waste recycling centres within close distance of your site.UK Recycling is the nationwide division of Waste cycle. As the leading Waste management company in the Midlands, Waste cycle understands the difficulties of segregation on site, aggravated by the management of sub-contractors and the need to meet tight deadlines.
A number of plastic manufacturers have been exploring different alternatives to plastics made from non-renewable fossil fuels. Such “bio-plastic” alternatives include polymers made from plant sugars and plastics grown inside genetically modified plants or microorganisms. These include polymers such as cellulose. Cellulose can be used to make such plastics as cellophane. This is a thin plastic film normally used in packaging.
The evidence above supports Alan because it shows that plastics are lightweight, cheap, tough and durable and this corresponds with his statements. This does not support Susie as the information is not relevant to her statement.
Disadvantages of plastics
Plastics are recyclable materials, but unfortunately people do not realise this. Plastics make up 7% of household waste when they could go to more useful causes if you just recycle them.
The disposal of plastics products can contribute significantly to the environment. This is because most plastics are non-degradable. 57% of litter found in England 2003 was recyclable plastic. The amount of plastic waste generated annually in the UK is estimated to be nearly 3 million tonnes. According to a 2001Environment Agency report, 80% of post-consumer plastic waste is sent to landfill, 8% is incinerated and only 7% is recycled. Disposing of waste in a landfill involves burying the waste. A properly-designed and well-managed landfill can be a hygienic and relatively inexpensive method of disposing of waste materials. However older, poorly-designed or poorly-managed landfills can create a number of adverse environmental impacts such as wind-blown litter, attraction of vermin. Another common byproduct of landfills is gas (mostly composed of methane and carbon dioxide), which is produced as organic waste breaks down anaerobically. This gas can create problems associated with smell, kill vegetation, and is a greenhouse gas. This will therefore contribute to global warming which is a problem in itself. In addition incineration is a disposal method that involves combustion of waste material. Incineration is a controversial method of waste disposal, due to issues such as the emissions of gas pollutants. This also contributes to global warming and is therefore a problem.
Plastics production requires large quantities of energy resources to produce them, primarily fossil fuels. It is estimated that 4% of the world’s oil supply is used as a feedstock for plastic production and an additional 3-4% during manufacture. This puts huge strain on oil refineries to produce enough crude oil to satisfy the needs of these demands. Therefore crude oil supplies could run out quicker than we ever imagined. In addition, the consumption of crude oil means there will be an increase of carbon emissions; this will therefore lead to an increase in global warming.
The information above supports Susie because it says that “Plastics have littered everywhere for years.” This is proven in my research because I have shown how most plastics are non-degradable are therefore thrown away in bins which are taken to landfill. This does not support Alan because the information is not relevant to his statement.
Practical Work
The aim of our practical was to prove/test Alan’s theory, that plastics are tough and durable. We did this by adding weights to strips of plastic bags and finding out its breaking point.
The method we used was:
- To use a 30cm ruler as a template and draw around it three times on a plastic bag to make three identical strips of plastic. (These plastic strips we used needed to be identical in order to make the experiment more valid.)
- After we had the three templates, we cut them out.
- Once we had the strips of plastic, we added weights to one of the strips very carefully on hangers until the plastic strip snapped. (We kept the strip as flat as possible to make ourselves more reliable.)
- Once the strip snapped we counted the mass of weight in grams and made a note of it, then converted it into kilograms and Newton’s.
- We then repeated this with the two other strips of plastic.
- Once we had the results for the other two strips, we averaged our results therefore making ourselves more reliable.
- After that we compared our results with other people in order to make ourselves more reliable
Here was the table we used to collect our data:
Average force needed to break your plastic: 45.75 N
(I have not included the results of the first strip in the averaging because these results were not completed, we ran out of time for that one)
Averages collected from other groups:
From the data we collected in this experiment I can conclude that plastics are tough and durable. This is because we added 4.75 and 4.4 kilograms to the strips of plastic before they were able to break, which suggests that they are strong also. We were valid in this experiment because we controlled all the variables, we had the same people doing the same jobs and we used the most accurate equipment e.g. 30cm ruler and took repeat readings. We were reliable in this experiment because we followed a valid plan as shown above, we took averages and we compared our results with the other groups.
From the data collected from all of the groups that did this experiment I can conclude that that collectively plastics are not tough and durable because only two bags, the Shell and Boots bags are tough because they could hold a lot of mass however the Clintons, M & S and Game were not. This is because they are not use to carry heavy products.
The above research supports Alan because it shows that plastics are tough and durable and we have evidence that proves this. This does not support Susie as the information is not relevant to her statement.
Summary
Overall, the research I have gathered supports Alan more than Susie. This is because I have researched both points of view and gathered evidence which supports both Alan and Susie, however the evidence is more in favour of Alan as there is more evidence which indicates that “Plastics are a great modern invention because: They are lightweight, cheap, energy saving, tough and durable.”For example, plastics can be used as a cheaper and more cost effective way for building materials. These materials can be used for such items as guttering. This also proves that plastics are durable because gutters last for quite a lot of years.
I think that plastics are a great benefit to us as they can be useful for multiple reasons, especially plastic bags. This is because they can be reused again and again and are therefore very durable. This is proven in my research from my results table of my practical work.
Glossary
Hydrocarbons – An organic compound containing just hydrogen and carbon
Fractional Distillation – An industrial process used to separate the constituent parts of crude oil
Fraction – A constituent part of crude oil, produced by fractional distillation
Alkane – A hydrocarbon in which all the bonds between the carbon atoms are single
Alkene – A hydrocarbon in which two or more carbon atoms are joined by double bonds
Cracking – A type of chemical reaction in which large alkane molecules are decomposed to form smaller alkanes and alkenes
Monomers – A small molecule, for example an alkene that can be joined to many other small molecules to form a large molecule
Polymerisation – A chemical process that combines several monomers to form a polymer
Thermosetting – A polymer which cannot be melted or remoulded again once formed
Thermoplastic – A polymer which softens or melts when heated up and becomes hard again when cooled
Biodegradable – Capable of decaying through the action of living organisms
Non-Renewable – Cannot be replaced of reused after use
Non-Degradable – Incapable of degradation or decomposition
Recycle – To treat or process waste materials so as to make them suitable for reuse
Plasticiser – A substance added to polymers to make them softer and more flexible. Plasticisers allow polymer chains to slide over each other more easily
Bibliography
Cracking – Page 108/109 Edexcel GCSE Additional 360 Science textbook
Fractional Distillation - Page 168/169 Edexcel GCSE 360 Science textbook
Polymerisation - Page 110/111 Edexcel GCSE Additional 360 Science textbook
Thermosetting and thermoplastics – Page 110/111 Edexcel GCSE Additional 360 Science textbook
Uses of plastics -
Varieties of plastics -
Metal to plastic conversion -
Benefits of plastics -
Development of bio-plastics -
WC 7 well written and structured, good bibliography and glossary
A 7 Very good scientific research including types of plastic, biopolymers and recycling schemes. Good analysis of data.
A+I 6 good discussion of Alan and Susie throughout, implications and applications well discussed.
Total 20 A
Marked LAW 28/2/10