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 doin 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 realised i bin thinkin that an increase in temp would make the ball harder lol, so infact when the ball gets hotter doesnt it recieve the energy to break the bonds of some of the cross links in the pllymer and therefore become more flexible and therfore bouncier
im guessing the slower balls have more crosslinks