WETTABILITY OF WOOL ASSEMBLIES

Abstract

Wool fibers purified by scouring show intensive water repellency caused by the epicuticle of the surface scale. Therefore wool assemblies absorb no water even when they are immersed statically for a long time in water at ambient temperature.In this study, wool assemblies were immersed in various kinds of liquids to find the wetting condition. Changes of wetting behaviour with the degree of porosity of wool assembly were discussed.The experimental procedures and the appraisals of wettability of sample wool assembly are as follows.Sample assemblies suspended from a strain gauge were immersed into liquid. Apparent weights of the sample assembly in the liquid were followed by the strain gauge as a function of elapsed time and the relations between retained air index (Va/Vc) and elapsed time were obtained. Rapid convergence of Va/Vc value to zero means the high wettability of the sample assembly.The results are as follows:1) In distilled water, the water did not enter into assembly, regardless of temperature and degree of porosity.2) In the mixtures of water and ethanol in various ratios, penetration of the liquid became fast in proportion to the decrease of surface tension of the liquid. In 55vol.% ethanol solution, of which surface tension was 31.2dyne/cm, Va/Vc value converged to zero, very rapidly. From these facts, we suggest that C. S. T. value of wool surface is in the range 30 to 35dyne/cm.3) In surfactant solutions of different concentrations, the penetration rate increased in proportion to the concentration. But in the dilute concentration range below the critical micelle concentration, the penetration of liquid was very slow.4) In tetrachloroethylene, penetration completed within a few second, at any degree of porosity. The solvent shows excellent permeability to the wool assembly.