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Physics, Astronomy & Cosmology / Re: How can plastic, which is often light, end up at the bottom of the sea?
« on: 04/10/2016 10:52:51 »
It depends on the type of plastic; air-filled polystyrene foam is unlikely to sink.
Most plastics are manufactured from hydrocarbons, and oil floats on water, so you could guess that many hydrocarbon plastics will float on water.
But some plastics also contain Fluorine (eg Teflon) or Chlorine (eg Poly VinylChloride: PVC), and this will increase the density beyond a pure hydrocarbon. Some of these plastics are much more dense than water (water=1 g/cm3, or slightly higher for sea water).
See: http://www.dotmar.com.au/density.html
Note that some plastics are slightly porous, and water may penetrate the plastic over weeks, slowly increasing the density until it sinks.
Most plastics are manufactured from hydrocarbons, and oil floats on water, so you could guess that many hydrocarbon plastics will float on water.
But some plastics also contain Fluorine (eg Teflon) or Chlorine (eg Poly VinylChloride: PVC), and this will increase the density beyond a pure hydrocarbon. Some of these plastics are much more dense than water (water=1 g/cm3, or slightly higher for sea water).
See: http://www.dotmar.com.au/density.html
Note that some plastics are slightly porous, and water may penetrate the plastic over weeks, slowly increasing the density until it sinks.
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