Re: Why do mylar balloons shrink more than latex balloons in cold air?

Charle's Law describes the relationship of a volume of gas and the 
temperature.
V1 / T1 = V2 / T2
V1 / V2 = T1 / T2

Where: V1*T2=V2*T1
V1&2 equals the Volume of gas
T1&2 equals the Temperure Kelvin
K = C + 273

1 liter of gas at 22 C will equal what volume at 0 C?

1*273=V2*295
273/295 = V2 = 0.9L

Now I'll assume that your experiment didn't fill the 2 balloons with the 
same volume of gas which may account for the unrecognizable difference. 
Next time you perform the test, grab a ruler and mark a 50 millimeter line 
on the balloon and then place the balloon in the freezer. Give the balloon 
a little time to come to temperature. Quickly remove the balloon from the 
cold and quickly measure the line. The line should get smaller due to the 
volume of gas decreased. Oh and please don't pop your balloon with a sharp 
pen!

The difference between mylar and latex is the material's ability to 
stretch. Mylar doesn't stretch quite like latex. Therefore you can push 
more volume of gas into a latex balloon. 

I agree that liquid Nitrogen would cause a considerable difference.
Liquid Nitrogen boils at 77 K (−196 °C/−321 °F), 
From the liter of gas above
1*77=V2*295 
77/295 = V2 = 0.3L
A very large difference.

Please be careful when using Liquid Nitrogen. 
The material is very very cold and could quickly cause frostbite. 
But the greatest danger is nitrogen's ability to displace the needed oxygen 
in the area of use. Use adequate ventilation or take the experiment 
outside.

Keep up the good work.... and never stop learning.