Measuring paper wetting processes with laser transmission

Abstract

We introduce a method to measure paper wetting based on the measurement of monochromatic (670 nm) light transmission through paper. The samples were 49.8–51.7 g m−2 handsheets, the hydrophobicity of which was tuned by the fibre content of the furnish. In addition, one of the samples was internally sized. Impact wetting with isopropanol and water mist pulses was applied. The duration of a pulse was 100 ms, and the amount of liquid per pulse was 12.6 ± 1.2 g m−2. Optical changes in a paper sample were detected by measuring the average intensity of transmitted light through a selected area. The results showed that different wetting processes (pure capillary and combined capillary and diffusion wetting) could be distinguished from each other. With the presented method, differences in the individual behaviour of the samples during wetting could also be seen.

Transmission of ultraviolet light through reinforcement fabrics and its effect on ultraviolet curing of composite laminates

“…For the glass fiber fabrics, wetting with polyester resin changes the transmission significantly. The same effect was discussed in detail by Karppinen et al [19] for the transmission of visible light through wetted paper. For dry fabrics, multiple diffuse reflections of incident light occur at each interface between the individual fibers and the surrounding air.…”

Accessibility of fiber surface sites for polymeric additives determines dry and wet tensile strength of paper sheets

“…We compare the treatment of paper samples with a light-sensitive copolymer (Toomey et al 2004;Janko et al 2015;Jocher et al 2015;Bump et al 2015) using an impregnation process with three different solvents. The solvents were chosen based on literature-data of cellulose fiber swelling (El Seoud et al 2008;Karppinen et al 2004) because we were particularly interested in the use of solvents, that don't lead to significant fiber swelling, in comparison to water. The latter is known for its capability to significantly swell paper fibers thereby altering the morphology.…”

Caracterização de propriedades de papel para impressão por jato de tinta.

“…O espalhamento, e subsequente penetração de líquidos em papel, pode ser visto como a soma de quatro subprocessos coexistentes (Karppinen et al, 2004):…”