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Q & A: Easy to find insulators

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Most recent answer: 10/22/2007
Q:
What are the best "easy to find" thermal insulators for cold temperatures?
- Angel (age 12)
A:
Styrofoam's pretty good at insulating materials at all temperatures below a couple of hundred degrees Fahrenheit. We put liquid nitrogen in styrofoam cups and pick them up all the time. (We don't drink the stuff of course -- that's really dangerous). Dry ice is commonly distributed in ordinary coolers which are often just plastic boxes with styrofoam or other insulation between the walls.

Fiber materials also work well -- wool, cotton and poleyster are common materials which are used as insulators. They don't work too well when wet, though (styrofoam works even when holding a liquid), and so are not recommended for liquid nitrogen use. In fact, they can be worse than no insulator because cloth that is soaked in liquid nitrogen held next to your skin will damage your skin much more than letting the liquid nitrogen roll off. The fibers are quite effective for making coats and other clothing items to keep you warm.

Fiberglass insulation is common in homes. The fiber insulation is good because it conducts heat badly (very little cross-sectional area per fiber, poor heat conduction along a fiber, and poor contact between fibers), and they also stop convection effectively, by keeping the trapped air from circulating inside. Air can blow through some fiber products, which is why coats and insulation and other stuff usually has a shell of material on the outside to prevent wind and rain (and possibly liquid nitrogen) from getting through.

Tom

(published on 10/22/2007)

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