Drying and film formation of industrial waterborne latices

Abstract

Experimental evidence is given for the mechanism of film formation from industrial waterborne latices using Inverse‐Micro‐Raman‐Spectroscopy (IMRS). In the vertical direction of the film drying is gas‐side controlled, indicated by uniform water concentration profiles. In the horizontal direction inhomogeneous drying resulting from a horizontal mass flux toward the edge of the film and the formation of a drying front are observed. The completeness of film formation is tested by so‐called IMRS redispersion experiments. For hard latices (Texperiment ≃ Tmff) particle deformation is incomplete and the final coating—although transparent and optically clear—is a porous structure with a network of surfactant material located at the particle interfaces. The use of a film‐forming aid lowers the polymer's minimum film formation temperature (Tmff) and facilitates particle deformation and polymer interdiffusion. The result is a nonporous film structure where individual particles and a network of surfactant material are no longer observed. IMRS redispersion experiments are compared with pictures of the final coating surface obtained from atomic force microscopy (AFM). © 2007 American Institute of Chemical Engineers AIChE J, 2007

Measuring the Drying Rate of Liquid Film Coatings Using Heat Flux Method

“…Before the liquid deposition (Regime I), the test fluid was preheated to the initial substrate temperature, and the measured flux shows a nonzero constant value q S 0 , which is attributed to the sensible heat flux in air in Eq. (6). The subsequent coating operation resulted in a rapid decrease in substrate temperature and an increase in the heat flux (Regime II).…”

“…The conventional gravimetric method, [1][2][3] by which a coating weight loss per unit area is measured over time, is often disturbed by fluctuations of the flowing air and is thus limited to low drying rates. Although recent progress in infrared [4,5] and confocal Raman [6] spectroscopies has enabled us to quantify local solvent concentrations in evaporating multicomponent liquids, careful calibrations are usually required for each chemical species. Furthermore, the need for optical transparency at the wavelength of interest often limits the applicability of these techniques to samples $10 mm thick or less.…”

Effect of soluble polymer binder on particle distribution in a drying particulate coating

“…The evaporation speed is proportional to the molar flux of solvent that is transported to the gas phase, _ n s , and can therefore be modeled by applying the Stefan-Maxwell equations for unidirectional diffusion in a binary system [20][21][22] …”

Coat formation of surface-active proteins on aqueous surfaces during drying

“…Drying of a film is a necessary simplification in this investigation to allow an experimental analysis using inverse micro Raman spectrometry (IMRS). With the IMRS used in this work, the local concentration of components within a dried film can be obtained quantitatively with an optical resolution of 2-3 m [14,15]. X-ray photoelectron spectroscopy (XPS) sputter-depth profiling is used to measure local concentrations of protein and carbohydrate in the near surface region (nanometer range) of the dried film.…”