KS3 Science Video: Stephanie Kwolek and composite materials

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KS3 science video: Stephanie Kwolek talks about her invention of new polymer material Kevlar.

In this short KS3 science video (3.32 mins), Stephanie talks about her life, how she became a chemist and her research at DuPont. Stephanie invented a new new polymer fibre at DuPont, called Kevlar which is five times stronger than steel.

Kevlar is used in composite materials, where it is layered with other substances such as rubber.

View the video

Properties of Kevlar

  • Kevlar is a polymer. This means that it is made up of long chains of individual molecules (monomers) joined together –  a bit like a chain of paperclips. The individual chains are held together very strongly by forces of attraction.
  • It’s tensile strength (the force that a material is able to withstand when being stretched) is very high but its compressive strength (the force that a material can withstand when being crushed) is low.
  • Kevlar doesn’t melt. It breaks down (decomposes) at a temperature between 427-482°C.
  • Kevlar has a density of 1.44 g/cm3. This is much less than steel’s density which is 7.80 g/cm3.
  • It is also five times stronger than steel.

Some questions you could ask your students

  • Use the information about its properties to explain why Kevlar is used for each of these applications:
  • Fuel tanks of Formula 1 cars.
  • Body armour.
  • String for tennis rackets.
  • Fire-fighter’s clothing
  • Explain why Kevlar is not used for building bridges.

More free resources on composites and compounds …

Video source: http://invention.smithsonian.org