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)
