Since "Styrofoam" is actually a brand name (see http://en.wikipedia.org/wiki/Styrofoam), you might be better off going with the generic name of the material: polystyrene foam.

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Note added at 15 mins (2009-06-16 01:07:20 GMT)
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The original bill pretty much banned coolers with this language: “No person shall possess foam or Styrofoam, polypropylene, expanded polypropylene or polystyrene coolers on or within fifty feet of any river . . .”

http://blog.jeffcitylaw.com/?p=814

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Note added at 16 mins (2009-06-16 01:08:38 GMT)
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Foam Coolers Prohibited on Riverways starting 2007

Ozark National Scenic Riverways has announced that starting May 1, 2007, all polystyrene foam type food and beverage coolers typically known as “Styrofoam” coolers will be prohibited on the Jacks Fork and Current Rivers within the Riverways boundary. This includes all polystyrene coolers with an exterior foam coating or coolers made of solid foam.

http://nps.gov/ozar/parkmgmt/upload/WEBNR 050 styrofoam coolers on rivers.doc

The price leads me to think that it is not a polystyrene cooler but rather a polyurethane cooler. Short life.
Polyurethane has a longer life but the price is much higher.
Modern fridges, freezers, coolers and thermal aislation use polyurethane as it can easily be expanded inside a form.


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Note added at 1 hr (2009-06-16 02:14:30 GMT)
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Acording to the description provided, the coolers must be hardy so the use of polystyrene for the coolers is not an option. The cooler will be used day after day. See modern use of polyurethane for coolers in the following pages.

http://www.chinasuppliers.globalsources.com/china-suppliers/...
Polyurethane Cooler Box China Manufacturers & Suppliers

http://north.manufacturer.globalsources.com/si/6008804471442...
Foam CFC-free Polyurethane Cooler Box with Capacity of 15L and 40W ±20% Hot Mode. ...

http://www.websters-online-dictionary.org/Wi/Wine cooler.htm...
damper, polyurethane cooler; wine cooler. ...

http://www.couriersupply.com/catalog/courier_shippers
36517, 22130208, Small Polyurethane Cooler, 6-7/8" x 3-3/8" x 13", 10" x 6-3/8" x 15-1/2" ... 36519, 22130210, Large Polyurethane Cooler, 17" x 9-1/2" x 13" ...
http://www.sphinxpanel.com/sp_walkinclrs.htm
The foamed-in-place polyurethane cooler wall and ceiling panel .

http://www.fullbooks.com/Roget-s-Thesaurus-of-English-Words-...
polyurethane cooler refrigerador

http://www.forensicmag.com/newsletters/archive/January/Foren...
This rigid polyurethane cooler is inert to methanol, liquid nitrogen, dry ice and salt and will not rust, leak or sweat. (Bel-Art) ...

http://www.bonn-cooling.com/mobile3.htm
This high-density polyurethane cooler can be customized to fulfill your widest possible range of cooling needs.


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Note added at 15 hrs (2009-06-16 15:57:17 GMT)
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Styro foam and polyurethane foam are both expanded plastics, where a gas is generated inside the plastic mass.
The only difference is that polyurethane foam is more durable.
Same foam production methodology, different hardiness.

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Note added at 16 hrs (2009-06-16 17:09:49 GMT)
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Kate, do not let this difference bother you.
There are so many common use artifacts that have traditional names that really do not represent its content that I would disregard the problem straight away.
If the article is to be read by any one, do not bother with technicalities at all.
If it is technical, the use is optional.
If it is highly technical then the matter changes and the correct term should be used.