.In addition to solvent evaporation and critical micellar concentration, we show the capillary transport velocity to be a crucial factor for mesopore formation in paper using sol-gel chemistry. Pores are generated at the fiber inner and outer surface.
Research into paper-based devices and ionic liquids has increased considerably in the past few years. Thus, the combination of paper-based devices with ionic liquids is also becoming an increasingly frequent research subject. However, the influence of the ionic liquid on the paper properties has been hardly considered. In this paper, the influence of a hydrophobic ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide) on the mechanical properties of laboratory paper, isotropic and oriented, made from eucalyptus sulfate and cotton linters, is investigated. The tensile strength, elastic modulus, and breaking strain of papers saturated with ionic liquid were about 60 to 90% of the dry paper characteristics. In contrast to water, the breaking strain did not increase in the presence of the ionic liquid. This is because the ionic liquid only slightly swelled the fibers.
The aim of this work is to investigate the influence of fiber fibrillation and fines on the pore structure of well-defined regenerated fiber sheets as well as the water flow through the sheet. For this purpose, sheets were produced with refined, fibrillated fibers only, with unfibrillated fibers and fines, as well as with fibrillated fibers and fines. Next, the samples were analyzed by brightfield and fluorescence microscopy, mercury porosimetry, and an ascending test. Both the fibrils and the added fines reach into the pores between the fibers or are deposited there. As a result, pore size decreases and capillary flow slows down. The two effects overlap when the fiber surface is fibrillated and fines are present. Sheets with thicker fibers form a pore structure with larger pores in between the fibers. However, such a change in pore size has no significant influence on the flow of water through the sheet in the performed ascending tests. It is shown that a statistical model with the parameters fibrillation and fines content can be used to describe the ascending rate nearly as well as the Lucas–Washburn equation. Consequently, the equation could be improved by the addition of further fiber and sheet properties.
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