What are plastics made from?
Polymers.
What is a polymer?
A polymer is a large molecule made from lots of monomers joined together.
What is polymerisation?
The process of monomers joining together to form a polymer.
What is addition polymerisation?
The process by which polyethene and other polymers are made, due to many monomers (ethene molecules) added together.
How does addition polymerisation occur?
- Ethene molecules have a double covalent bond between the carbon atoms
- One of the bonds in the double bond breaks open and another ethene molecule adds on
- This process happens again and again, forming a long chain
What is n?
A very large number.
What are examples of naturally occurring polymers and how are they produced?
- Starch: polymer made from glucose
- Proteins: polymer made from amino acids
- DNA: polymer made from 4 different monomers (nucleotides)
What are some uses and properties of polymers?
Check teacher notes diagram SC24b slide 13.
What are esters?
A homologous series with a ‘fruity smell’. They are found naturally in fruits but are artificially made on a large scale.
What are the properties of esters?
- Immiscible (insoluble) with water
- Volatile (low boiling point so evaporate easily, hence the reason why we can smell them easily)
How are esters produced?
Carboxylic acids react with alcohols in the pressure of a catalyst to make esters. This is a condensation reaction.
What are uses of esters?
- Cosmetics (e.g. perfumes)
- Food flavourings
- Solvents (e.g. nail varnish remover, board markers)
- Making plastic bottles (lightweight and can be recycled)
- Made into fibres which can be woven into fabrics
What are polyesters?
Long-chain molecules containing many ester molecules joined together.
How are polyesters formed?
By condensation polymerisation in which the monomers join together and eliminate a small molecule (e.g. water).
What are three ways of disposing polymers?
- Recycling
- Incineration (burning)
- Disposing in landfill
Why can plastics not be decomposed by bacteria in the soil?
Plastics are non-biodegradeable.
What advantages and disadvantages do we have from using polymers?
Disposal in landfill sites:
Advantage - Easy to do
Disadvantage - uses valuable land; loss of animal habitats; polymers do not rot (non-biodegradable)
Disposal by burning:
Advantage - produces energy/electricity
Disadvantage - produces carbon dioxide; may produce toxic gases
What are the solutions to environmental problems with polymers?
- Reducing the amount of materials we use
- Re-use materials
- Materials that cannot be reused anymore can be recycled by processing it to make a new item
State an example of a biodegradable plastic.
Polylactide is a plant-based polymer. These are often made from starch that has been modified to become more stable.
