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

I am a general science teacher for grades 6-8.  We recently did an experiment 
where we blew up 2 balloons and left one in the classroom and put one in the 
refrigerator (the kids actually put them in the freezer - I found out later). 
After about 30 minutes they got them out - the book I was using said they 
would shrink.  They didn't appear to.  They really may have been smaller if we 
had examined more carefully - maybe by using a tape measure etc... but we ran 
out of time.  I don't think this experiment will make a lasting impression on 
my students.  I know about & am teaching Charles' law to them.  I know that 
when a mylar balloon is in the cold, the shrinking is very noticable - why the 
difference between latex and mylar???  I'm thinking it has to be something 
about their composition - the latex is a better insulator?  I really thought 
we may see a more drastic change.  I know you can use liquid nitrogen and the 
latex balloon will really shrink, then expand when back in room temp. - is it 
that the temperature in the freezer wasn't cold enough?  Help!

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