Wettability of Porous Materials III: Is the Wilhelmy Method Useful for Fabrics Analysis?

Woven and nonwoven fabrics and the corresponding fibers have been analyzed using a Wilhelmy microbalance. A self-developed analysis software (written using Labview flow-data language) has been used to extract the advancing and receding angles and also other informations commonly neglected by the standard data analysis of Wilhelmy technique, such as the immersion cross-sectional area, the effective wet perimeter, the liquid absorption, the parallelism of the straight lines describing the immersion and the withdrawal of the sample in a typical force vs immersion graph. This approach has previously been proposed for rigid porous materials such as stones and wood with some success. In the present cases some modifications of the approach have been introduced to take into account the specificity of the materials. The results appear promising for the more rigid nonwoven fabric, but suffer from a greater uncertainty and from even unacceptable inconsistencies in the case of the softer and traditional fabric. Through the application of the proposed method and software to the Wilhelmy approach the precision of the measurements can be increased in the most common cases and may help in estimating wettability. This remains true even for soft fabrics, although in this case some very important limitations of the experiment and of the model are unable to eliminate systematic errors, with the consequence that only a qualitative estimate of contact angles can be achieved.