Determining the advancing and receding water contact angles of single textile fibers through a micro droplet probe

Conventional methods that measure the wetting properties of single fibers only yield the static contact angles or are unviable for thin, flexible, and highly hydrophobic fibers. This study evaluates a novel droplet probe method to determine the advancing and receding contact angles of single fibers. A horizontally suspended fiber is moved towards a millimeter-sized hanging droplet, to gradually increase the wetting length, and then retracted until detachment. The evolution of the wetting length is recorded, and the footage is analyzed to obtain the contact angle between droplet and fiber throughout the event. Six synthetic or cellulosic textile fibers were measured: polypropylene, polyester, polyamide, viscose, Lyocell, and Ioncell®. It showed a clear distinction between different fibers, with the advancing and receding contact angles being 122.9° and 115.7°, respectively for polypropylene, and 50.0° and 44.1° for Lyocell. Thus, detailed wetting properties are determined on the fiber level, decoupled from further processing steps such as yarn spinning and fabric construction. The gained insights are useful for the development of fibers with tailored properties or coatings and finishes for fibers.