title: Short time spreading and wetting of offset printing liquids on model calcium carbonate coating structures.
abstract: Spreading of oils and water on porous and pre-saturated model carbonate coating structures was studied with high speed video imaging. The short-time data were complemented with long time absorption and wicking experiments. The results indicate a strong dependence between surface structural features of the pigment tablets and water spreading at short times, both in non-saturated and water pre-saturated cases, while the oil spreading is mainly dependent on the liquid properties. Sodium polyacrylate dispersant on pigment surfaces is shown to contribute to water spreading and absorption. On pre-saturated structures the liquid-liquid interactions are dominant and the majority of results support spreading according to the molecular kinetic model. The evidence supports the hypothesis of S. Rousu, P. Gane, and D. Eklund, ["Influence of coating pigment chemistry and morphology on the chromatographic separation of offset ink constituents," in The Science of Papermaking Transactions of the 12th Fundamental Research Symposium, FRC The Pulp & Paper Fundamental Research Society, Oxford, UK, 2001, p. 1115] that at long times the oils absorb into the porous structure at a rate proportional to the ratio of viscosity and surface tension, provided there is no sorptive action with the binder. A combination of nanosized pores and large surface area is useful for providing sufficient absorption capability for carbonate based coatings.
authors.affiliation: Center for Functional Materials, Abo Akademi University, Department of Chemical Engineering, Abo/Turku, Finland. hanna.koivula@abo.fi
authors.forename: Hanna
authors.initials: H
authors.lastname: Koivula
authors.forename: Martti
authors.initials: M
authors.lastname: Toivakka
authors.forename: Patrick
authors.initials: P
authors.lastname: Gane