Free-volume evolution in the system polycarbonate-polycaprolaptone studiedby positron annihilation spectroscopy

Positron annihilation spectroscopy (PAS) can measure the free-volume proper ties in polymeric materials. In this paper PAS has been used to follow the free-volume evolution in several samples of polycarbonate (PC) with differe nt contents of polycaprolaptone (PCL) and different annealing times at 418 K. Results show that an increase in the content of the PCL added to the sam ple decreases the free-volume radius present in the PC. From the data obtai ned it can be observed that the free-volume radius is linearly dependent on the content of PCL in the range 0-10%. of PCL. An increase in the annealin g time at 418 K also produces a decrease in the free-volume radius of the s amples. However, the relative variation in the free volume of the samples i s much less than the change produced by the PCL. (C) 2001 Elsevier Science B.V. All rights reserved.