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9.5. Option - Polymers : 4. Synthetic polymers remain in the environment for a long time
| Syllabus reference (October 2002 version) | ||
|---|---|---|
| 4. As synthetic polymers are
not natural substances they do not decompose but remain in the environment
for a long time |
Students learn to: |
Students:
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Extract from Senior Science Stage 6
© Board of Studies, NSW.
[Edit 12 May 11]
Prior learning: ScienceStages 4–5
Background information: Unlike their
natural counterparts, most synthetic polymers are not biodegradable (i.e. decomposed
by micro-organisms). They do not rot, nor are they broken down by the action
of weather. In some cases this can be an advantage, but it can cause problems
The recycling of synthetic polymers can
save energy, raw materials and prevent damage to the environment.
identify that micro-organisms are part of the natural environment and their role as decomposers is vital in the ecosystem, with particular emphasis on the recycling of matter in ecosystems
- A micro-organism (microbe) is a very small (microscopic)
living creature.
Examples of micro-organisms are fungi (moulds and yeasts) and bacteria.
- The environment is the conditions in which a plant or animal lives.
- An ecosystem is a group of living things, together with their environment.
- A decomposer is an organism that feeds on and breaks down organic compounds, which are then returned to ecosystems to be re-used.
- Matter, including nutrients are recycled with the help of micro-organisms.
The major nutrient cycles are those involving
oxygen, carbon, nitrogen and water.
apply
the term biodegradability to those substances which can be decomposed by
micro-organisms.
- A substance that is biodegradable can be broken down by the action of living things such as micro-organisms.
gather,
process and
analyse secondary information, to assess the viability of
recycling plastics including those with additives such as
– stabilisers
– plasticisers
– fire-retardants
- Gather information from places like Clean Up Australia
NSW,
the Vinyl Council of Australia and the LEAD Action News . You could
use a search engine to gather more information. Your local or school library
may also have some suitable books.
- A good way to analyse information is to structure the information in a table. Well-designed tables assist you to identify trends, patterns and relationships. Try using a table to analyse the information from the notes provided below.
Backgroud information
Organisations may not recycle plastics if it is not a viable (eg financially worthwhile) process.
The cost of recycling the plastic needs to be compared with cost of manufacturing new plastic.
The quality of the recycled plastic may not be high.
Environmental considerations need to be taken into account – ie recycling may be “better” than landfill or other methods of disposal.
Some objects may be made of a mixture of plastics (and other materials) and be difficult to recycle.
Plastics that are not “pure”, but contain additives may be more difficult to recycle.
- Stabilisers are added to plastics to help them keep their original properties.
- Plasticisers are added to plastics to make them more flexible.
- Fire retardants are added to decrease the flammability of plastics.
gather and process information from secondary sources to present local government regulations on recycling of plastics in the local area
- To gather this information ring your local council and ask for the Health and Environment section. Ask if they have some information to send you. If they do not , arrange to have an interview with the appropriate person.
- When you have enough information, process it by arranging it in a logical order. You might draw up a table with the different grades of plastic in the left hand column and then record how that grade is treated by your council. Most councils will recycle plastic containers with the numbers 1,2 and 3 in the recycle triangle. Plastic bags are not taken by curbside recycling but some supermarkets will take them.
Background information
Local governments have a responsibility to collect and dispose of waste.
Many local authorities have a policy of recycling materials including plastics.
Many local authorities supply (and collect) containers specifically for recyclable materials.
Councils may consider methods to encourage people to recycle, such as charging extra if waste is over a particular weight.
There may be different regulations for domestic and industrial waste.
compare
the relative biodegradability of natural and synthetic polymers and assess
the impact of synthetic polymers in aquatic and terrestrial environments
- Because synthetic polymers are durable, easily shaped and coloured, they have been widely used for packaging. Disposal of this plastic packaging (and other plastic products) can cause problems as they don’t break down easily.
- Natural polymers include such materials as cotton,
wool, cellulose and silk.
Natural polymers have substances such as amino acids and glucose as their monomers. Because of their chemical make-up, many natural polymers are biodegradable.
- Aquatic environments are those involving water, eg
ponds, rivers and dams.
Terrestrial environments are those in or on the ground. Organic matter needs moisture, warmth and air to be decomposed.
- Plastics are not broken down quickly by weather, i.e.
heat, cold, wind or rain.
Plastics are not digestible by living creatures.
- Plastic that is thrown away is often buried as landfill.
Burying is not a particularly good solution as plastics do not decompose quickly
and landfill takes up large areas of land. However if plastic is made from
biodegradable material the problem of filling up landfill and contaminating
the soil will not occur. Some information on this can be found at Reactive
Extrusion Processing and Extrusion Polymerization Chemical Engineering
and Materials Science, Michigan State University, scroll down to Biobased
Thermoplastics and Thermoset composites.
- Some plastics contain substances that may cause damage
as these plastics eventually break down. Some materials, lost or thrown away,
such as polythene bags, nylon fishing lines or nets, can remain as a danger
to wildlife for many years, especially those in water bodies such as rivers
and oceans. Dangerous
Debris and What YOU can do about it See the sea.org, Salinas, California,
USA
gather,
process, analyse
and present information, to perform
a first-hand investigation to determine the amount of plastic material that
is thrown out per day at school or at home.
- To gather information you will need to look in the bins at school or at home.
- At school, bins to look in include bins in classrooms, playgrounds and near canteen facilities. Before you start looking make sure you have strong plastic gloves and keep an eye out for anything sharp that may cut you.
- Tip the contents on a plastic sheet and then separate the plastic from the other rubbish.
- Process the information by recording it in
a table. The headings could be:
Source, Type of plastic, Amount, Recyclable.
- Analyse the information in the table.
- Investigations should take place over several days
so as to obtain reliable results.
The amount of plastic could be measured by number of items, volume or weight.
- Present the information in table form, pie charts (sector graphs) column graphs (bar charts) or histograms.
- Issues that could be raised include:
- what types of items are most common
- were there any differences between households?
- what were the differences between school and home?
- could some of the plastic items be recycled?
gather
and process first-hand information and information from secondary
sources to describe the coding system developed by industry to aid
the identification and recycling of plastics
- Before plastics can be recycled they have to be identified and sorted.
- There are so many plastics in common use that consumers are unlikely to recognise them all.
- Plastics manufacturers have come up with a code.
- The plastic item is stamped with a number from one to seven within a triangle.
- Collect a range of plastic items and identify them using the coding system described.
- Look in the library or on the internet to find more
information about coding and recycling. Some questions to answer might be:
- Has this code only been developed for Australia or are the symbols international?
- Which industry developed the code, the packaging or recycling industry? Are they different?
- What is the significance of this code to the recycling industry? Eg. Does it make recycling easier or save money?
discuss some of the issues involved in recycling plastic materials, downcycling and the uses of recycled plastics
- The use of plastics worldwide has grown from about 5 million tonnes in the 1950's to around 100 million tonnes today due to their being lightweight, versatile, inexpensive and durable.
- There are hundreds of different varieties of plastics and all types are recyclable but only types 1 and 2 in the table above are currently recycled by kerbside collections carried out by most local councils, with some councils collecting number 3.
- As more recycled plastic is used so more will be required.
Some current uses of recycled plastics are:
- wheelie bins
- outdoor furniture
- compost bins
- timber substitute planking used in jetties and walking tracks
- pipes
- pots for plants.
- However these products have to have some new plastic material in them. A common mix is 75% new and 25% recycled.
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