Why does a rubber band shrink when heated with a hairdryer?

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SUMMARY

The forum discussion centers on the behavior of rubber bands when subjected to heat, specifically using a hairdryer. When heated in air, the rubber band shrinks despite the expectation that heat would cause it to expand, as observed in hot water. This phenomenon is attributed to the material properties of rubber, which can undergo permanent deformation when heated in the presence of a weight. The discussion also references the concept of "heat shrink tubing" as a related example of this behavior.

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IB tired
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Hmm...some experimenting led to an interesting result. I attached a weight to a rubber band and suspended the rubber band in some hot water. The rubber band expanded. I repeated the experiment in cold water and the band shrank. An expected result, yes? Well I redid the experiment in air and I got something totally different. I used a hairdryer and heated the band with the weight on it and the band shrunk...anybody care to explain why?
thanks!
:)
 
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Do you have an estimate (be close) of the temperatures involved?
 
IB tired said:
Hmm...some experimenting led to an interesting result. I attached a weight to a rubber band and suspended the rubber band in some hot water. The rubber band expanded. I repeated the experiment in cold water and the band shrank. An expected result, yes? Well I redid the experiment in air and I got something totally different. I used a hairdryer and heated the band with the weight on it and the band shrunk...anybody care to explain why?
thanks!
:)

Maybe google to see how "heat shrink tubing" works. Note -- the rubber band's length was permanently changed by the hot air, correct?
 

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