Investigation of Gas Permeation and Free Volume Hole Properties of Polyurethane Membranes by Positrons

摘要

Positron annihilation lifetime measurements have been carried out for hydroxyl terminated polybutadiene (HTPB), hydroxyl terminated polybutadiene/styrene (HTBS) and hydroxyl terminated polybutadiene/acrylonitrile (HTBN) based PU membranes at room temperature. The average ortho-positronium (o-Ps) lifetime, its intensity and average free-volume hole volume (V{sub}F) were calculated using two phase model. We found that average hole volume decreased with the increase of hard segment content. On the other hand, direct relationship between the gas permeability and the free volume has been established.