composites, ceramics, polymers revision

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  • Created by: kotriux
  • Created on: 21-06-17 19:20

composites

Composites

  • composites are made from two or more different types of materials.
  • Materials for composites are chosen because they have different properties that combine to make more useful materials.

Composite material examples

  • MDF- made from wood fibres and glue, fibreglass is made from mesh of fibre glass set intough polymer.
  • Steel-reinforced concrete- made by pouring concrete around a mesh of steel cables, when set, material is: strong when streched (because of the steel) and squashed (because of the concrete). 
  • Waterproof clothing made from nylon.
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Polymers

  • Most polymers are held together with covaelant bonds.
  • All atoms in a polymer are joined together by strong covaelant bonds.
  • Intermolecular forces between polymer molecules are larger meaning more energy is neede to break them , so most polymers are solid at room tempertaure.
  • The intermolecular forces are still weaker than ionic and covaelant bonds so thehy have lower boiling points than ionic or giant molecular forces.
  • Polymers are made by chemical reactions that join lots of small molecules together to make long molecules.
  • General properties of polymers: chemically unreactive, solids at room temperature, plastic (can be moulded into shape), electrical insulators, strong, hard-wearing.

For diagram visit: http://www.bbc.co.uk/education/guides/ztxnsbk/revision/2

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Ceramics

Key info and ceramic materials

  • They're non-metal solids with high temperatures and they're not carbon based
  • some ceramics are made from clay.
  • Solids made by baking a starting material in a very hot oven 
  • Are hard and tough
  • have very many different uses
  • Ceramic materials are coated in a tough glaze in bathrooms. They are hard and tough, and waterproof.

Clay and glass

  • clay is soft when dug out of ground can be moulded
  • when fired at high temperature clay hardens to form a type of ceramic, clay
  • glass is transparent moulded when hot but brittle when thin
  • most galss- made of soda lime glass (heated mixture of limestone, sand + sodium carbonate)
  • broscilater glass- higher melting point than soda lime glass, made in the same way but with and boron trioxide
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