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Science

Designer polymers

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A lot of everyday items are made from polymers. Many of these polymers are not biodegradable - microbes cannot digest them and they take a long time to break down. Polymers are usually disposed of by burying them in landfill sites or burning them in incinerators. These methods of disposal cause environmental problems, and waste valuable resources.

The properties of polymers depend on the structure and bonding found in their molecules. Smart materials such as Gore-Tex® have more useful properties than other polymers.

Polymer properties and uses

Monomersmonomer: A monomer is a simple molecule. can join together to form polymerspolymers: Polymers are large molecules formed from many identical smaller molecules (monomers).. Additional polymers are formed from alkenes. For example:

  • ethene can polymerise to form polyethene, which is also called polythene
  • styrene can polymerise to form polystyrene.

Ethene makes polyethene

Typical uses for polythene include plastic shopping bags and plastic bottles, while polystyrene is typically used for insulation and protective packaging.

Branches

Polymer molecules can have branches coming off them, which change the properties of the polymer. You should be able to suggest the properties a polymer has for a particular purpose. The table compares two types of polythene.

Two types of polythene

LDPE

low-density polyethene

HDPE

high-density polyethene

branches on polymer moleculesmanyfew
relative strengthweakstrong
maximum useable temperature85 ºC120 ºC

HDPE is more suited for use in making disposable cups for hot drinks, for example.

Other polymers

Some polymers are not made from alkene monomers and these are called condensation polymers. Nylon and polyesters are examples of this. They can be drawn into very fine fibres and woven into cloth for clothing. Often, natural fibres such as cotton are mixed with nylon or polyester fibres to make a soft but hard-wearing cloth.

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