Studies on the free volume and the volume expansion behavior of amorphous polymers

In order to estimate the free volume contribution on the volume change, we investigated the relationship between the volume expansion behavior by Pres sure-Volume-Temperature measurement apparatus and the free volume behavior by Positron Annihilation Lifetime Spectroscopy for some amorphous polymers. From these results, the free volume fraction of the amorphous polymers was calculated by assuming that the core volume increases at a constant rate w ith temperature. It was found that the amount of free volume was not consta nt even in the glassy state and it played a very important role in the volu me expansion. (C) 2000 Elsevier Science Ltd. All rights reserved.