WATER IN URETHANE ACRYLATES .1. SORPTION AND DESORPTION PROPERTIES OFURETHANE ACRYLATE-CO-GLYCOL ACRYLATE NETWORKS

Sorption and desorption kinetics of water uptake in urethane acrylate and urethane acrylate-coglycol acrylate networks are reported and anal ysed in terms of Fick's and Frisch's laws. The Frisch parameter n calc ulated for sorption ranged from 0.4 to 0.6, while that for desorption ranged from 0.5 to 0.8. Two-stage sorption for some samples at low rel ative humidities was interpreted in terms of water clustering within t he polymer, promoted by a high ratio of hydrophobic groups to polar wa ter-solubilizing moieties.