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

[IB tired]

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!
:)

 

[Lok]

Do you have an estimate (be close) of the temperatures involved?

 

[berkeman]

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?