WILHELMY PLATE STUDIES OF CARBON-FIBER VISCOUS-FLUID SYSTEMS

The use of Wilhelmy plate techniques for studying the interactions of fibers with fluids of variable viscosity is discussed. The influence o f hydrodynamic effects on force (F) vs. depth (z) plots is interpreted on the basis of surface tension-independent added terms of the consti tutive equation of the Wilhelmy experiment. Wetting experiments using pseudoplastic fluids (polyethyleneglycol/water solutions) show that vi scoelasticity is indeed important in the interpretation of Wilhelmy pl ate experiments. The comparison of wetting experiments performed on un treated and plasma-treated carbon fibers showed that at low stage spee d and fluid viscosity, surface chemistry and morphology determines con tact angles. At higher stage speeds and viscosities the advancing and receding angles are affected by surface chemistry-independent and hydr odynamics-dependent added contributions.