Polymer

Polymer

  1. Polymer is a large molecule that is in the form of a long chain with a high relative molecular mass (RMM).
  2. It is made up of many smaller units called monomers, which are joined together through a process called polymerisation. Thus the monomer is actually the repetitive unit of a long polymer chain.
  3. There are two types of polymers:
    1. Natural polymers
    2. Synthetic polymers

Natural Polymers

  1. These occur naturally in living things. Some examples of natural polymers are:
    1. Natural rubber
    2. Protein in meat, leather, silk, hair and fur
    3. Carbohydrates in cellulose, starch and sugar
  2. Natural polymers are made up of carbon, hydrogen, nitrogen and oxygen.

Synthetic Polymers

  1. Synthetic polymer is a polymer that is manufactured in industry from chemical substances through the polymerisation process.
  2. Examples of synthetic polymers are:
    1. plastics
    2. synthetic fibres
    3. elastomers 
  3. The two types of polymerisation are:
    1. polymerisation by addition
    2. polymerisation by condensation


Polymerisation

  1. Polymerisation is the process of joining together the large number of monomers to form a polymer.
  2. There are 2 types of polymerisation process
    1. polylerisation by addition
    2. polylerisation by condensation

Polylerisation by Addition

Polymerisation by addition involves monomers with >C = C< bonding, where the monomers join together to make a long chain without losing any simple molecules from it.


Polylerisation by Condensation

  1. Polymerisation by condensation involves the elimination of small molecules like water, methanol, ammonia or hydrogen chloride during the process. 
  2. Examples of products of this process are terylene and nylon-66.



Plastics

  1. Plastics are light, strong and do not react with any chemical substances, like acids and alkalis.
  2. They can be made into many shapes and sizes.
  3. They are also good insulators of heat and electricity.

Examples of Plastics:

Polythene (polyethylene)

Structure

Monomer: Ethene
Produced by polymerisation: Addition
Uses: Plastic bags containers and cups
Advantages:  light and strong

Polyvinyl chloride or PVC (polychloroethene)

Structure

Monomer: Chloroethene
Produced by polymerisation: Addition
Uses: Raincoat, Pipes to insulate electric wires
Advantages: can be coloured; heat resistant

Polystyrene (polyphenylethene)

Structure

Monomer: Phenylethene
Produced by polymerisation: Addition
Uses: Packaging materials,  children toys, ball-point pens, as heat and electric insulators
Advantages: light and strong

Perspex (polymethyl 2-methyl propenoate)

Structure

Monomer: Methyl-2-methylpropenoate
Produced by polymerisation: Addition
Uses: Aeroplane window panes,  Lenses, car lamp covers
Advantages: light, strong, translucent, stable towards sunlight

Polypropene

Structure

Monomer: Propene
Produced by polymerisation: Addition
Uses: Plastics, Bottles, plastic tables and chairs
Advantages: strong and light

Teflon (polytetrafluoroethene or PTFE)

Structure

Monomer: Tetrafluoroethene
Produced by polymerisation: Addition
Uses: To make non-sticky pots and pans
Advantages: hard, can withstand high temperatures and corrosives chemicals

Synthetic Rubber

  1. Synthetic rubber is an elastomer or polymer which regains its size original shape after being pulled or pressed. [Natural rubber is an elastomer too.]
  2. Examples of synthetic rubber are neoprene and styrene-butadiene(SBR).

Neoprene

Structure

Monomer: Chloroprene
Produced by polymerisation: Addition
Uses: to make rubber gloves and to insulate electric wires.


Styrene-butadiene or SBR

Structure

Monomer: Styrene and butan-1,3-diene
Produced by polymerisation: Addition
Uses: to make tyres, soles of shoes and mechanical belts.


Synthetic Fibre

  1. Nylon and terylene are synthetic fibres which undergo the condensation polymerisation process.
  2. These fibres resemble natural fibres but more resistant to stress and chemicals, and more long-lasting. 
  3. In both cases, water is eliminated during the polymerisation process.


Nylon

Structure

Monomer: 
Produced by polymerisation: Condensation
Uses: To make umbrellas, carpets, comb, curtains, nylon string and rope, socks, toothbrush and so on.


Terylene

Structure

Monomer: 
Produced by polymerisation: Condensation
Uses: To make fishing nets, clothes (quick-dry, non-iron), cassette and video tapes.

Issue in Using Synthetic Polymers

  1. Synthetic polymers have multiple uses in daily life because of the following properties:
    1. Light and strong
    2. Relatively cheap
    3. Withstand corrosion and chemical reaction
    4. Withstand action of water
    5. Non-flammable
    6. Can be colour easily
    7. Easily mould to shape
  2. Synthetic polymers are also used to replace natural polymers such as cotton, silk and rubber.
  3. However, synthetic polymers cause environmental pollution.
    1. Most polymers are not biodegradable . Disposal of polymers has resulted in environmental.
    2. The open burning of plastics gives rise to poisonous and acidic gases like carbon monoxide, hydrogen chloride and hydrogen cyanide. These are harmful to the environment as they cause acid rain.
    3. Burning of plastics can also produce carbon dioxide, too much of this gas in the atmosphere leads to the `greenhouse effect’.
  4. These problem can be overcome by the following ways:
    1. Recycling polymers: Plastics can be decomposed by heating them without oxygen at 700°C. This process is called pyrolysis. The products of this process are then recycled into new products.
    2. Inventing biodegradable polymers: Such polymers should be mixed with substances that can be decomposed by bacteria (to become biodegradable) or light (to become photodegradable).