Wettability of four Asian meranti species

Summary

The wettability of four Asian meranti species (dark red, light red, white, and yellow) in various liquids was studied by a cone-immersion technique. Wettability was expressed in terms of the area under the force-immersion curve and referred to as the wettability index. Wettability was strongly influenced by the pH of the solution, generally increasing with increasing pH. Surfactant type affected wettability, with the cationic type yielding the greatest wettability followed by anionic and nonionic types. Among the liquids used, distilled water gave the lowest, and acetone-isopropyl alcohol solution gave the greatest wettability. Of the meranti species, yellow meranti showed the greatest wettability, followed by white, light red, and dark red meranti.

A plot of the relative amount of liquid absorbed into the wood sample versus wettability index yielded two regions, one attributed mainly to liquid trapped in crevices on the wood surface, and another which may be more indicative of wood-liquid interactions. A highly significant linear correlation between wettability index and liquid surface tension was found for those species with low and medium wettability, while that with high wettability showed no correlation. A new empirical approach of determining the critical surface tension of wood is discussed. Limited data for the present method indicated close agreement with result from the literature obtained by the use of the well-known Zisman's contact angle approach.