Short-time water absorption by model coatings
2008 (English)In: TAPPI Advanced Coating Fundamentals Symposium Proceedings, TAPPI Press, 2008, p. 204-216Conference paper, Published paper (Refereed)
Abstract [en]
Absorption of aqueous solutions into paper and board coatings is important in a number of printing technologies, not only inkjet printing but also flexography where aqueous based inks are frequent, and offset printing where the aqueous fountain solution has a strong impact on printability. An important difficulty in studying absorption into coatings is the small void volume of the coating which is in the order of a few cm3 per square meter for coatings designed for offset printing, but significant larger for coatings designed for inkjet paper. This paper presents a newly developed technique where it is possible to measure the absorption of very small amounts of aqueous solutions. In this technique a small droplet (=330 pl) is fired against the paper surface where it flattens out and forms a sessile drop with a height of about 40-50 μm. The base is constant during the absorption course studied. The absorption is calculated from the change in height and considering the drop-substrate contact area. This paper describes the technique in some detail, and the findings from absorption studies using model coatings containing various pigments (carbonate, clay, silica, polystyrene) in combination with different binders (various latexes, starch, PVA). Some systems showed a very fast absorption including an instant absorption that occurred within 8 ms. Almost all systems had an initial absorption rate that scaled linearly with time indicating an inertial flow regime. A transition occurred for many systems where the absorption process went into a regime where the absorption scaled linearly with the square root of time, indicating a viscous controlled regime according to the Lucas-Washburn equation and/or a diffusion controlled regime. This transition was promoted by swelling hydrocolloids such as starch and PVA within the coating.
Place, publisher, year, edition, pages
TAPPI Press, 2008. p. 204-216
Keywords [en]
Absorption, Clay minerals, Coatings, Drops, Geologic models, Lithography, Offset printing, Polystyrenes, Printing, Printing machinery, Printing presses, Silica, Solutions, Starch
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:ri:diva-29655Scopus ID: 2-s2.0-57649132132OAI: oai:DiVA.org:ri-29655DiVA, id: diva2:1105146
Conference
TAPPI Advanced Coating Fundamentals Symposium; Montreal, QC; Canada; 11 June 2008 through 13 June 200
Note
cited By 9
2017-06-022017-06-022020-12-01Bibliographically approved