Observation of the Effect of Wetting Efficiency on a Flow of Liquids Impinging on Solid Substrates by Fluorescence Depolarization

Abstract

Steady-state fluorescence depolarization has proven, in the past few years, to be a method sensitive to adhesion of thin liquid films flowing without boundaries on solid substrates of different chemical constitutions. This work extends our prior preliminary assessment of the efficiency of the method and the influence of experimental variables. Ten thin films of ethylene glycol (MEG) were mapped over 102 mm2 by polarized laser-induced fluorescence (PLF−FI) while flowing on substrates. The interfacial tension, ΓSL, was varied either by changing the chemical constitution of the substrate (borosilicate, tin dioxide, poly(vinyl alcohol) (PVA), and linear alkylbenzene sulfonate (LAS)) or by addition of tensoactives to MEG (sodium dodecyl sulfate (SDS) and poly(ethylene oxide) (PEO)). Contact angle measurements were employed to classify interfaces according to their static ΓSL, that is, their wetting efficiencies. PLF−FI experimental variables, such as laser power, film thickness, and impinging velocity profile, did not alter the data within the range studied, except for flow rates over 220 cm s-1. Average polarization (P av) increased from 10.5% to 13.5% upon decreasing adhesion by varying the chemical constitution of the solid. When surfactants were dissolved in the liquid flow, polarization ranged from 5.4% to 3.8% while for surfactant as substrate it increased. Simple multivariate principal component analysis (PCA) was applied to downstream polarization averages (P down) for each map. The two principal components accounted for 95.6% of the variance, ordering the maps according to decreasing adhesion and gathering them into three groups: dissolved surfactants, liquid films flowing at the highest flow rate, and solid surfaces of different chemical composition. Hierarchic cluster analysis (HCA) showed that, as adhesion decreased, similarity among the polarization maps increased.

Polymeric Surfaces for Heavy Oil Pipelines To Inhibit Wax Deposition: PP, EVA28, and HDPE

“…For the same liquid, the interfacial tension is proportional to the cosine of θ c . It is known that θ c depends on the surface roughness, on the chemical nature of both the solid surface and the liquid, − and on the relative orientation of the surface chemical groups …”

Wettability under Imposed Flow as a Function of the Baking Temperatures of a DGEBA Epoxy Resin Used in the Crude Oil Industry

“…ΓSL has been determined for many decades under static or slow flow conditions by sessile drop contact angle (θc) measurements . It is known that θc depends on surface roughness, on the chemical composition of both the solid surface and the flowing liquid, − and on the relative orientation of the surface chemical groups . Extrand proposed a simple thermodynamic model for free energies of wetting obtained from the θc of small sessile drops spread on a solid surface and found reasonable agreement with bond strengths measured by other experimental methods.…”

Fluorescence Depolarization Investigation of the Lobed Jet 90° Twists and Structural Features

“…They have channel length of 40 mm and slit apertures of 6 mm × 300 μm and 6 mm × 500 μm. The liquid jet consists of Merck 99.5% ethylene glycol (MEG), chosen for its physical properties such as viscosity and low evaporation rate and widely used in fluorescence depolarization studies. ,,, The liquid's temperature was kept at (14.0 ± 0.2) °C. Jet net velocities were obtained by dividing the volumetric rate by the nozzle channel area.…”