Multicycle Wilhelmy Plate Method for Wetting Properties,Swelling and Liquid Sorptionof Wood.

A multicycleWilhelmy plate method has been developed to investigatewetting properties, liquid sorption, and swelling of porous substratessuch as wood. The use of the method is exemplified by studies of woodveneers of Scots pine sapwood and heartwood, which were subjectedto repeated immersion and withdrawal in a swelling liquid (water)and in a nonswelling liquid (octane). The swelling liquid changesthe sample dimensions during measurements, in particular its perimeter.This, in turn, influences the force registered. A model based on alinear combination of the measured force and final change in sampleperimeter is suggested, and validated to elucidate the dynamic perimeterchange of wood veneer samples. We show that pine heartwood and pinesapwood differ in several respects in their interaction with water.Pine heartwood showed (i) lower liquid uptake, (ii) lower swelling,(iii) higher contact angle, and (iv) lower level of dissolution ofsurface active components (extractives) than pine sapwood. We concludethat the method is also suitable for studying wetting properties ofother porous and swellable materials. The wettability results weresupported by surface chemical analysis using X-ray photoelectron spectroscopy,showing higher extractives and lignin content on heartwood than onsapwood surfaces. [ABSTRACT FROM AUTHOR]