Effect of temperature on a squash ball

[destinct]

hey,my gf is doing the effect of temperature on a squash ball expt and i started thinkin about it (im doing physics at uni(and this makes me sound sad dunt it lol)) but why does it bounce higher when hot...is it because the air inside heats up and therefore there is a higher pressure? but i was thinking about the different types of ball aswell, so would they have a different remperature co-efficent and dissapate the heat faster and therefore the balls with a higher temperature co-efficent be 'slower' balls or another idea...is it to do with the properties of the material ie, some type of thermo setting polymer and the balls have different temperatures at which they set, therefore the 'faster balls would have a lower setting temperature', its been a while since i did solid materials

 

[destinct]

i just realized i bin thinkin that an increase in temp would make the ball harder lol, so infact when the ball gets hotter doesn't it receive the energy to break the bonds of some of the cross links in the pllymer and therefore become more flexible and therefore bouncier
im guessing the slower balls have more crosslinks