Comparison of the surface energetics data of eucalypt fibers and some polymers obtained by contact angle and inverse gas chromatography methods

This study compares two approaches to determine the surface energy of solid s, and its acid-base components in particular: inverse gas chromatography ( IGC) and analysis of contact angle data using the Good-van Oss theory. The comparison is made in the context of wood fibers from Eucalyptus globulus a nd Eucalyptus regnans,ls pulped by the kraft and neutral sulfite semi-chemi cal (NSSC) processes, and of selected polymers. Contact angles on wood fibe rs were measured using the Wilhelmy method and on polymer samples using the sessile drop technique. For the dispersive component of the surface energy , the level of agreement between the two approaches was reasonable, using a lkanes for the IGC measurements and diiodomethane for the Wilhelmy and sess ile drop techniques. However, agreement was poor for the acid and base char acteristics when monopolar probes were used for IGC and water, formamide, a nd diiodomethane for contact angle measurements. The Good-van Oss approach suggested that all fibers and polymers are monopolarly basic, whereas IGC m easurements suggested that they are bipolar. When new values were used for the acid and base components of the surface energy of the liquid probes bas ed on the values for water proposed by Della Volpe and Siboni, all samples still appeared strongly basic. This is inconsistent with the chemical natur e of the lignocellulosic fibers. Thus, the Good-van Oss approach provides a poor indication of acid-base properties of the surfaces of solids in sugge sting that lignocellulosic fibers and polymers are strongly basic. The abov e issues as well as potential problems in measuring the surface energy of l ignocellulosic fibers using the three-liquid procedure and the Good-van Oss approach are discussed.