Une nouvelle interprétation de l'hystérèse de mouillage des polymères

Centre de Recherches sur la Physico-Chimie des Surfaces Solides, C.N.R.S., 24, avenue du Président Kennedy, 68200 Mulhouse et Laboratoire de Recherches sur la Physico-Chimie des Interfaces de l'Ecole Nationale Supérieure de Chimie de Mulhouse, 3 rue Alfred Werner, 68093 Mulhouse Cedex, France.

Résumé

L'hystérèse de mouillage de polymères de différentes natures chimiques a été déterminée par mesure des angles de contact à l'avance et au retrait dans un système à deux phases liquides non miscibles. Cette hystérèse est directement proportionnelle à la polarité superficielle des solides et peut être attribuée à un phénomène d'orientation des groupements fonctionnels de surface des polymères.

Abstract

Contact angle measurement constitutes a simple, rapid and sensitive method of characterisation of the surface properties of solids For a given solid, liquid and fluid environment, one would expect a unique value for the contact angle at the triple line. However, in practice, a given system will often display a range of contact angles between a lower limit, θr, or receding angle, and an upper limit, θa, or advancing angle. This difference is often referred to as hysteresis. Several reaons for wetting hysteresis have been suggested in the past, notably the inhomogeneity of the solid surface composition and its rugosity. Nevertheless, these would seem to be inadequate to explain wetting hysteresis on polymers. A study has therefore been undertaken to correlate hysteresis and the intrinsic polar nature of polymer surfaces. An original method using a two-phase liquid system has been employed in which polymer polarity and hysteresis may be estimated simultaneously. An undeniable correlation has been obtained between the two parameters. This has been attributed to the potential orientation of polar sidegroups on the polymer long-chain molecules near the liquid-solid interface.