How well is the hair wettable before and after a wash? How compatible is a mineral fiber with the polymer of a composite material? Does a textile fabric print well? Answers to these seemingly unrelated questions are provided by contact angle measurements on biological, mineral, or synthetic fibers. With the new Meniscus method for the Drop Shape Analyzer product family, KRÜSS solves this measurement task optically.
Precise optical measuring method
In a Meniscus measurement, the fiber sample is immersed vertically in a liquid phase. This can be a standard test liquid or a sample directly relevant to the question, an ink for instance. The capillary force creates a meniscus along the fiber, which forms a characteristic contact angle at the three-phase point (solid-liquid-gaseous) that depends on the wettability. This contact angle is determined by the high-resolution camera of the Drop Shape Analyzer used and the precise evaluation algorithm of the ADVANCE software.
One method, many answers
When equipped with a software-controlled feed, the contact angle can also be determined during immersion and withdrawal in order to record the wetting and dewetting process on the basis of the advancing and receding angle. This allows, for example, conclusions to be drawn about the adsorption of the liquid on the fiber. Results with several test liquids pave the way for calculating the surface free energy to establish a wettability and adhesion profile towards polar (water-like) or non-polar (oil-like) liquids. Moreover, the same test setup can be used to optically determine the fiber diameter.
More flexibility for optical contact angle measurement
Until now, fiber contact angles have been measured primarily based on wetting force using tensiometers. Thanks to the optical access now available, users of a Drop Shape Analyzer can solve many fiber-related problems with little investment, switching quickly between the new method and the standard measurement on the sessile drop.
The user-friendly fiber holder accessory SH3220 with a sample preparation set is now available. The associated meniscus module is available for the new version 1.18 of our ADVANCE software.