CH 11: The Development of Plastics for the Future

Question 1

What is the main non-renewable material used in the production of plastic?

Answer 1

Crude oil

Question 2

What are the uses of plastics?

Answer 2

1. Food and drink packaging.
2. Mobile phones, tablets and other electronic devices.
3. Clothes.
4. Window frames.
5. Electrical cables.
6. Toys.

Question 3

What is the main use of plastics?

Answer 3

Packaging

Question 4

What is the trend in the global production of plastic each year?

Answer 4

Continues to increase

Question 5

What are the 2 main uses of crude oil?

Answer 5

Transportation - fuels such as diesel and petrol.
Energy sectors - fossil fuel power plants to produce electricity.

Question 6

What is the name of the process required to convert crude oil into the feedstocks required for plastic manufacture?

Answer 6

Fractional distillation

Question 7

What is the name of the molecules in crude oil?

Answer 7

Hydrocarbons

Question 8

How is feedstock is obtained from crude oil?

Answer 8

Crude oil undergoes fractional distillation to separate it into different substances including gases that can be used to make plastics.

Question 9

How is the feedstock prepared for storage before use?

Answer 9

The gases obtained by fractional distillation are cooled and liquefied because liquids are much easier than gases to store, transport and use.

Question 10

What fraction of crude oil is used for the production of plastics?

Answer 10

Naphtha

Question 11

What are two pollution problems associated with the use of plastics derived from fossil fuels?

Answer 11

• Cannot be broken down by microorganisms.
• Incineration produces toxic materials.

Question 12

What are the toxic gases that may be released during the incineration of plastics?

Answer 12

• Carbon monoxide
• Hydrogen cyanide
• Hydrochloric acid

Question 13

Why do plastics cause pollution problems in the oceans?

Answer 13

Plastics cannot be broken down by micro-organisms or easily recycled so they build up in the environment creating pollution issues such as the great Pacific garbage patch.

Question 14

What are the advantages associated with plastics derived from naphtha?

Answer 14

1. Plastics are readily available in a range of colours and different mechanical properties.
2. They are currently very cheap. This has the unfortunate outcome of promoting buying a new item rather than the consumer choosing to get an item fixed or refurbished.
3. Can be formed and shaped into many various design forms from mobile phones, televisions to keys for your car.
4. Plastics are durable, which means they last a long time. A laptop made from plastic, while it may slow down over the years, will look and behave mechanically the same for decades.

Question 15

How can we overcome plastics taking hundreds or thousands of years to break down?

Answer 15

1. Increase the quantity of plastic recycled. This reduces the amount of crude oil required and so releases less greenhouse gases into the atmosphere. This also has the added advantage of sending less plastic to landfill.
2. Make plastic degrade quicker. It will be made apparent later in this chapter, that the manufacturing process can be altered to enable plastics to decompose much more rapidly in the environment.

Question 16

What is meant by the term ‘biodegradable plastic’?

Answer 16

Plastics that can be broken down by micro-organisms, bacteria or other biological means.

Question 17

What are the applications of biodegradable plastics?

Answer 17

1. Biodegradable plastics can be used as packaging for single use items such as carrier bags, food packaging and drink and food cartons for the takeaway food industry.
2. Films. Biodegradable plastic agricultural films as mulch can be used to supress weeds, increase soil temperature, prevent loss of water and minerals from the soil. It can be ploughed into the soil after use.

Question 18

What are the applications for photodegradable plastic and what are the impacts on crops or the environment?

Answer 18

• Plastic Mulch
  Used as a growth promoter for saplings. In forestry or poor land. Allows soil to be stabilised whilst sapling takes root in otherwise unstable soil.
• Coatings for slow release fertiliser / pesticide pellets
  Controlled release of active agent. Particularly where risk of leaching. Or where risk of run off is high.

Question 19

What are the drawbacks of applying fertiliser?

Answer 19

1. Low absorption of nutrients from the fertiliser into the soil, which causes economic losses in terms of a reduced yield.
2. The fertiliser pellet can be dissolved into liquid form and it then leaches into the soil. However, this leachate could be washed away by heavy rain into water courses, such as streams and rivers having a devastating impact on eco systems.
   3.The fertiliser on the soil surface can be transported away before it infiltrates the soil structure. This can happen in a flash flood that takes place shortly after spreading the fertiliser. This fertiliser can be transported to local water courses, such as streams and rivers having a devastating impact on eco systems.

Question 20

What is the process of the slow release fertiliser?

Answer 20

1. A fertiliser pellet is coated in a plastic which can be photodegradable.
   2.This fertiliser is applied to a field. Fields that are susceptible to leaching and or a high probability of surface run off, are particularly suitable.
2. Over a period of time, which can be determined and controlled by the plastic coating thickness, the fertiliser will diffuse through the plastic coating into the ground. The time periods can be as large as six to nine months, ensuring a more uniform distribution of nutrients to the crops as they grow. This considerably reduces the issues associated with leaching and surface water run off associated with traditional fertilisers, as the larger mass pellets are more difficult to displace in heavy rain.

Question 21

What is a piece of laboratory apparatus that could be used to measure the tensile strength of photodegradable plastics.

Answer 21

The Newton meter

Question 22

What additive can cause a plastic bag to degrade much faster?

Answer 22

Oxygen

Question 23

How can oxygen cause a plastic bag to be broken down at the end of its useful life?

Answer 23

Stage 1 – Additive is included in the basic polymer resin during the manufacturing process.
Stage 2 – Breaks the molecular chains so that at the end of its predetermined service life the plastic starts degrading in the presence of oxygen by a process of oxidation, which is accelerated by light, heat and stress.
Stage 3 – Bio-degradation is completed by microorganisms.

Question 24

How can a plastic can be modified during the manufacturing process to make it photodegradable?

Answer 24

It is manufactured to contain a chemical additive which absorbs light, attacks the polymer and breaks it down.

Question 25

What can be used in modern plastic manufacturing processes to improve biodegradability?

Answer 25

Option 1; Modification of the process to enhance thermal and photodegradation. Addition of different chemical links into long chain molecules of plastic which breaks up when hit by UV light. Option 2; Production of bioplastics. Addition of starch which is digested by microorganisms – breaks up plastics into smaller pieces. Option 3; Production of compostable plastics. Made from e.g. corn starch fully biodegradable and compostable.

Question 26

What are the agricultural uses of compostable plastics?

Answer 26

- Compostable plastics can be used to improve soil composition. They break down in the environment to provide useful soil nutrients. - They can be used as weed suppressant as they can cover ground around plants preventing weed growth. - They can be used as mulch keeping soil temperatures raised in winter / conserving moisture.

Question 27

How is bioderived polyethylene (BPE) produced?

Answer 27

A plant such as corn/sugar cane undergoes fermentation to produce ethanol. Ethanol is converted to ethylene (dehydration). Ethylene then undergoes (addition) polymerisation to form BPE.

Question 28

How is production of bioderived polyethylene (BPE) not a sustainable manufacturing process?

Answer 28

It is energy intensive process and energy used in its production will almost certainly come from a non-renewable source.

Question 29

What does BPE stand for?

Answer 29

Bioderived Polyethylene

Question 30

What are the global moves towards sustainable manufacture?

Answer 30

1. Manufacturing process - The energy required for the manufacturing process, through the operation of machines and the fractional distillation process, are likely derived from fossil fuels.  These are finite and so will run out. Additionally, they also pollute the atmosphere through greenhouse gas emissions. 2. Biodegradability - Many existing plastics derived from crude oil take hundreds, if not thousands, of years to degrade sufficiently.  Chemical additives can be added during the manufacturing process, to considerably reduce the length of time for the degradation process which occurs through either UV radiation (photodegradation) or microorganisms (biodegradation). This has the potential to greatly reduce waste at landfill and in the oceans of this planet.  But the microplastics formed are still a long-term concern. 3. Bioplastics - The production of plastics such as bioderived polyethylene, removed the need to use crude oil to produce plastics.  This reduces the need to extract crude oil which increases the duration that such fuel sources will last. It also removes any issues of sourcing these fuels from volatile nations.  Therefore, security of supply is increased for plastic production.  It also does not release greenhouse gases into the atmosphere as the biomass absorbs CO2 during the growing phase.

Question 31

What are the global moves towards sustainable use?

Answer 31

1. Single use plastics - This chapter has shown that as of 2015, some 381 million tonnes of plastic are being produced globally per year.  A very high proportion of this has been discarded after one use, especially in food packaging.  Reuse of plastic is paramount to reduce the quantity of plastics ending up in landfill sites and our oceans.  The next option must be recycling. 2. Recycling - When plastic cannot be used any more for its primary purpose, it should be recycled.  Segregation of the waste is critical for effective recycling to take place.  Effective recycling reduces the need to extract and manufacture more new plastic from crude oil or from biomass.  It also reduces the plastic going to landfill and our oceans.