FREE-VOLUME CHARACTERISTICS AND WATER-ABSORPTION OF NOVOLAC EPOXY-RESINS INVESTIGATED BY POSITRON-ANNIHILATION

A positron-annihilation lifetime technique was applied to four kinds o f epoxy resin (cresol novolac, tris-hydroxy-phenyl-methane (THPM), tet ra-methyl-biphenol and bis-phenol A) in order to study the relation be tween the intermolecular-space holes and water absorption. The sizes o f the holes were measured, based on the life-time (tau(3)) of the orth o-positronium. Since THPM has a larger tau(3) value (hence, a larger i ntermolecular-space hole) and absorption rate than that of the other s amples, a correlation between tau(3) and the absorption rate has been shown to be evident. Assuming a very simplified model, the shapes of t he holes for the smallest unit cell were calculated using a computer c ode of molecular dynamics; the shape for THPM was found to be differen t from those of the other three samples. Copyright (C) 1996 Elsevier S cience Ltd.