MEASURING THE SURFACE ENERGIES OF SPHERICAL CELLULOSE BEADS BY INVERSE GAS-CHROMATOGRAPHY

The effect of the chemical composition of regenerated cellulose solids on surface energy was studied by inverse gas chromatography (IGC). Th is was to probe a possible relationship between the ability of the cel lulose surface to interact with other phases through van der Waals for ces and its bonding potential, A model consisting of amorphous cellulo se spheres (''beads'') was used to eliminate all effects of morphology and geometry, The surface of the beads was modified by chemical react ion of the hydroxyl groups of cellulose. A thin layer of cellulose der ivative, such as cellulose trifluoroethoxyacetate (CW-TFEA), cellulose laurate (CW-LA), or directly fluorinated cellulose (CW-F), was produc ed on the bead surface, The surface properties of the cellulose beads were fully characterized by X-ray photoelectron spectroscopy (XPS), sc anning electron microscopy (SEM), and nitrogen adsorption, IGC was per formed using the adsorption of two kinds of probes: alkanes to measure the dispersive component of the surface energy (gamma(S)(d)), and aci d/base probes to quantify the specific adsorption enthalpy (Delta H-Sp ). The dispersive component of the surface energy of cellulose was fou nd to depend mostly on the presence and concentration of free hydroxyl groups on the surface. At low degrees of substitution (DS < 1), how t hese OH groups were replaced by modification, whether by fatty acid ty pe substituents or by fluorine-containing groups, was essentially irre levant for surface energies, The dispersive component of the surface e nergy (gamma(S)(d)) declined with DS almost irrespective of substituen t type. The surface of cellulose was found to be highly acidic, and th is was attributed mainly to the presence of hydroxyl groups.