ADSORPTION AND CONTACT-ANGLE STUDIES .3. ORGANIC-SUBSTANCES ON POLISHED POLYETHYLENE

Ellipsometrically determined adsorption isotherms are reported for ethanol, propanol, butanol, amyl alcohol, n-hexane, and diethyl ether on optically smooth polyethylene at 20°C. The contact angle behavior of the corresponding liquid substrates on the same surface was also determined. For the first four, nonwetting, cases, the film pressure of the adsorbed film is not negligible, and could not be neglected in semiempirical treatments of contact angle. Further, it appears that polyethylene surface is modified structurally by the adsorbates. The isotherms fit the potential-distortion model; they also fall on the same characteristic isotherm that previous nonwetting systems obeyed. The surfaces show microscopic roughness under scanning electron microscope examination, and the possibility that adsorption is mainly due to capillary condensation in surface dimples is examined. © 1979 Academic Press, Inc.