Polymer behavior with nanoindentation test

[generous]

Hello everyone, I'm glad to join the forums and enjoy some scientific discussions

 

I hope my question is not very specific...I've been reading since a while about nanoindentation of polymers...it is always reported that, longer holding times of the test (creep) leads to obtaining less values of stiffnes

 

similarly...faster unloading rates lead also to less stiffness...but the papers where i read that never mentioned the reason

 

any idea about the reason behind this, considering the creep and the chain movements and all this?

 

many thanks!