BARRIER AND SURFACE-PROPERTIES OF POLYURETHANE-EPOXY INTERPENETRATING POLYMER NETWORKS .2.

We have measured the advancing contact angles of drops of methanol‐ethylene glycol mixtures on films of previously studied polyurethane‐epoxy interpenetrating polymer networks. The extrapolated critical surface tensions were in excellent agreement with those obtained from advancing contact angles of drops of water‐methanol mixtures. A sharp minimum is observed in the critical surface tension at network compositions where we have previously found maxima in ultimate mechanical properties. We advance a physical explanation based on unrelieved surface strains. We have also measured the toluene vapor transmission (permeability, diffusion and sorption coefficients) in these films. These results, together with the previously obtained water vapor permeabilities, are in complete accord with the expected morphologies of these networks. Copyright © 1979 Society of Plastics Engineers, Inc.