The wetting of cellulose and wood hemicelluloses

The wetting properties of wood polysaccharides were characterized by Zisman's empirical parameter, the critical surface tension of wetting, γ c . Cellulose was tested in the form of cellulose films regenerated from viscose and cellulose acetate. It was found that the source of cellulose (cotton, wood and hydrolyzed cellulose), the method of film preparation (single‐bath, two‐bath, dry‐cast, orientation), and consequently the physical state of the cellulose surface, influenced the wettability of the samples. Contact angles were also measured on hemicellulose films derived from hardwoods and softwoods. The critical surface tension γ c ranged from 35.5 to 49.0 erg cm −2 for cellulose and from 33 to 36.5 erg cm −2 for hemicellulose films. The hemicellulose samples showed the smallest hysteresis effects which may be related to its energetically more uniform surface or lower porosity. The effect of moisture on contact angle measurements is discussed. Finally, the wetting of cellulose is evaluated in terms of recent theories relating surface energies and intermolecular forces.