Cookie policy: This site uses cookies (small files stored on your computer) to simplify and improve your experience of this website. Cookies are small text files stored on the device you are using to access this website. For more information please take a look at our terms and conditions. Some parts of the site may not work properly if you choose not to accept cookies.

Join

Subscribe or Register

Existing user? Login

Rubber’s odd behaviour

  • Print
  • Share
  • Comment
  • Save
  • Print Friendly Version of this pagePrint Get a PDF version of this webpagePDF

If, as mine sometimes does, your copy of The Pharmaceutical Journal arrives rolled up with other post inside a Royal Mail red rubber band, you might be interested to know that the first rubber band was patented in England on today’s date, 17 March, by Stephen Perry in 1845.

What is particularly interesting about rubber bands is their unusual behaviour when exposed to heat. This is due to the property in physics known as entropy, which describes the disorder in a system.

Heat causes rubber bands to contract, while cooling causes expansion. This is the opposite of the effect of heat on other substances, for example, water, which expands when heated.

Rubber, however, does not have a crystalline structure, which would allow its molecules to break apart when heated and enable expansion. Rubber is made from string-like molecules which when heated behave like strings of Christmas tree lights and get tangled, so causing a rubber band to contract.

Also counterintuitively, rubber heats when stretched. When you stretch rubber, the tangled molecules are pulled straighter into a straight line. Entropy (or disorder) is reduced and heat is given out. Stretch a rubber band and press it to your forehead and it will feel warm. Let it contract again and the rubber will feel cool as the molecules tangle, the entropy increases and the rubber sucks up heat from you.

Have your say

For commenting, please login or register as a user and agree to our Community Guidelines. You will be re-directed back to this page where you will have the ability to comment.

  • Print
  • Share
  • Comment
  • Save
  • Print Friendly Version of this pagePrint Get a PDF version of this webpagePDF

From: Beyond pharmacy blog

Take a look here for thoughts and musings beyond the pharmacy realm

Newsletter Sign-up

Want to keep up with the latest news, comment and CPD articles in pharmacy and science? Subscribe to our free alerts.