MadSci Network: Chemistry

Re: Mouthwash + Polystyrene = Small lump of plastic???

Date: Wed Jan 15 17:43:17 2003
Posted By: Chris Fellows, Post-doc/Fellow, Chemistry, University of Sydney
Area of science: Chemistry
ID: 1041131717.Ch

Polystyrene foam is basically a little bit of plastic (poly(styrene)) and a lot of air. A piece of polystyrene keeps its shape because the plastic is (relatively) hard and brittle. If it gets softer and more flexible, it will deform and squash down into a small lump of plastic.

Polystyrene molecules are very very long, and at room temperature polystyrene is hard because the large numbers of weak chemical bonds between these molecules hold them in a rigid matrix.

The main non-water ingredient of your mouthwash, isopropyl myristate, is somewhat soluble in polystyrene, and vice versa. While these molecules [ (CH3)2-CH-O-CO-(CH2) 12-CH3 ] will be unable to dissolve the plastic, enough will work their way in between the long molecules of polystyrene and make it easier for them to slide past one another, making the material soft and rubbery. Thus, over time, the original polystyrene foam will shrink down to a lump of plastic...

Current Queue | Current Queue for Chemistry | Chemistry archives

Try the links in the MadSci Library for more information on Chemistry.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2002. All rights reserved.