POLY(ETHYLENE-TEREPHTHALATE) SURFACE DYNAMICS IN AIR AND WATER STUDIED BY TENSIOMETRY AND MOLECULAR MODELING

The wetting characteristics of an amorphous poly(ethylene terephthalat e) (PET) film by water were studied by the Wilhelmy plate technique in the dynamic and static modes. At room temperature, a dynamic hysteres is of 40 degrees (theta(A) = 80 degrees, theta(R) = 40 degrees) was fo und. It was interpreted in terms of water adsorption-desorption phenom ena. The air-water and water-air equilibration processes of the PET su rface were studied. The static mode was most useful for this purpose. It showed that it takes about 10 days to reach equilibrium at 20 degre es C and that equilibration with water is only partially reversible. S urface restructuration was described by molecular modelling. The valid ity of this description was confirmed by a good quantitative agreement between experimental and calculated data. An increase of the temperat ure accelerates molecular rearrangements especially around the glass t ransition temperature of the polymer.