Dynamic water transport in a pigmented porous coating medium: Novel study of droplet absorption and evaporation by near-infrared spectroscopy

Carl-Mikael Tåg (Corresponding Author), Mikko Juuti, Kimmo Koivunen, Patrick A. C. Gane

Research output: Contribution to journalArticleScientificpeer-review

11 Citations (Scopus)

Abstract

The dynamic wetting of, and absorption into, model porous coatings in the form of compressed particulate pigment tablets by monocomponent, dual-component, and multicomponent liquid droplets has been studied by observation of apparent contact angle and near-infrared spectroscopy to identify the liquid water/moisture content. The absorption of the liquids was studied in a corresponding vapor-saturated environment. Liquid evaporation was determined for the tablets at both equilibrium starting pore saturation and under limited volume-filling conditions as evaporation proceeds. The changes in water and moisture content within the coatings as a function of time were also determined gravimetrically to relate the water uptake and evaporation being observed to changes in the near-infrared spectral data. Model and commercial offset printing fountain solutions were compared with respect to both absorption and evaporation. For the solutions containing isopropyl alcohol in water, a nonlinear behavior in the water response in the near-infrared spectra during absorption is observed as a function of time, which can be related to the fast evaporation of the alcohol. The nonlinear region was followed by a decline in water and moisture content as the penetration/evaporation of the water phase proceeded. Comparing the near-infrared water volume dependency in the upper layers of the structure with weight loss during evaporation showed that the mechanism of liquid transport to the surface−air interface reflected the logarithmic volume distribution of pore sizes, as might be expected from capillarity considerations and pore condensation hysteresis.
Original languageEnglish
Pages (from-to)4181-4189
JournalIndustrial & Engineering Chemistry Research
Volume49
Issue number9
DOIs
Publication statusPublished - 2010
MoE publication typeA1 Journal article-refereed

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