The effects of ultraviolet light exposure on the wetting properties of wood

With the aim to assess the viability of ultraviolet light irradiation as a surface pretreatment technique for activation, samples of two wood species, spruce (Picea abies Karst.) and teak (Tectona grandis), were exposed to ultraviolet light in ambient air. Contact angle measurements and scanning electron microscopy were used for the characterisation of these surfaces. After a specific exposure period to UV light radiation, the wettability and surface free energy (γS), especially the base component of γS, of radial and tangential wood surfaces of both species increased significantly. We presume UV irradiation to be an ablation process providing modification (cleaning) of the wood surface and opening the pits in spruce.