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| 3. |
- Vyörykkä, J., et al.
(author)
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Characterization of paper coatings - Review and future possibilities
- 2006
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In: 2006 TAPPI Advanced Coating Fundamentals Symposium. ; , s. 32-57
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Conference paper (peer-reviewed)abstract
- Paper coating obviously plays an important role in printing and converting performance and thus a thorough knowledge of coating structure and chemistry, its generation from the wet state of the colour layer and its reaction to downstream processing, end-use and recycling, is needed to understand current products as well as to develop new products. Coating characterization methods may be divided into two subcategories; research methods and quality control methods. The latter category typically contains methods based on standards and are fast tools to evaluate the quality of the coatings, on-line, at-line or off-line. The instruments used in paper coating research aim to provide absolute rather than relative information, with the goal of offering greater insight into mechanisms underlying paper performance. These methods are accordingly often more demanding in terms of sample preparation and analysis time, and in some cases are still under development. This paper summarizes the achievements, limitations and future challenges faced by established analysis methods as well as emerging methods which could be used in paper coating characterization.
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- Andersson, C, et al.
(author)
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Preparation and incorporation of microcapsules in functional coatings for self-healing of packaging board
- 2009
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In: Packaging technology & science. - 0894-3214 .- 1099-1522. ; 22:5, s. 275-291
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Journal article (peer-reviewed)abstract
- The replacement of flexible polyolefin barrier layers with novel, thin, functional polymer coatings in the production of paperboard packaging involves the risk of deteriorated barrier and mechanical properties during the converting process. Local defects or cracks in the protective barrier layer can arise because of the stress induced in creasing and folding operations. In this study, the incorporation of microencapsulated self-healing agents in coating formulations applied both by spot- and uniform-coating techniques was studied. The preparation process of microcapsules with a hydrophobic core surrounded by a hydrophobically modified polysaccharide membrane in aqueous suspension was developed to obtain capsules fulfilling both the criteria of small capsule size and reasonably high solids content to match the requirements set on surface treatment of paperboard for enhancement of packaging functionality. The survival of the microcapsules during application and their effectiveness as self-healing agents were investigated. The results showed a reduced tendency for deteriorated barrier properties and local termination of cracks formed upon creasing. The self-healing mechanism involves the rupture of microcapsules local to the applied stress, with subsequent release of the core material. Crack propagation is hindered by plasticization of the underlying coating layer, while the increased hydrophobicity helps to maintain the barrier properties.
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| 5. |
- Fogden, A, et al.
(author)
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Beyond the harmonic bending theory of ionic surfactant interfaces
- 1998
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In: Phys Rev E. - 2470-0053. ; 57, s. 5694-5706
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Journal article (peer-reviewed)abstract
- There is now a broad understanding of how electrostatics, described by the nonlinear Poisson-Boltzmann equation, contributes to the phenomenological coupling (bending) constants of the flexible surface model as applied to ionic surfactant interfaces when the curvature energy density is truncated at harmonic order. Here, we extend this to the constants associated with anharmonic terms, specifically at third order in the interfacial curvatures, using model aggregates of spherical and cylindrical geometry. We analyze in detail the two limits of excess added salt and counterions only, and also provide a simple construction for bridging these two extremes using the theory of theta functions. Further, we investigate the asymptotic nature of the curvature expansion for ionic membranes, showing that it progressively deteriorates as the aggregate curvature is increased, and offer an alternative approximation scheme for the full free energy, using the method of Pade approximants.
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| 6. |
- Nilsson, Helena, et al.
(author)
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Inkjet print quality on model paper coatings
- 2008
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In: Appita journal. - 1038-6807. ; 61:2, s. 120-127
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Journal article (peer-reviewed)abstract
- Laboratory paper coatings of simple composition, comprising only a single spherical plastic pigment and binder type, were analysed in terms of water-based inkjet print quality. Optical density and gamut of dye colours decreased with increasing pigment size, and followed the binder hierarchy from polyvinyl alcohol (best) to carboxymethyl cellulose to styrene-butadiene latex (worst). For the larger pigment size, density and gamut also decreased with decreasing binder content and increasing coat weight. Colour-colour sharpness was evaluated using four measures of line bleeding, of which mean line width and blurriness were found to be the most useful and well correlated. Both bleeding measures, while following the same binder chemistry hierarchy mentioned above, now worsened with decreasing pigment particle size. This tallies with expectations from capillarity and light scattering, e.g. increasing particle size (in the range studied) increases both liquid penetration rate and opacity, thus resulting in decreased colour richness but increased sharpness.
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| 8. |
- Persson, PV, et al.
(author)
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Silica nanocasts of wood fibres: A study of cell wall accessibility and structure
- 2004
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In: Biomacromolecules. - 1525-7797 .- 1526-4602. ; 5, s. 1097-1101
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Journal article (peer-reviewed)abstract
- The porosity and the available surface area of a lignocellulosic fiber can influence the accessibility and reactivity in derivatization and modification reactions because the porous cell-wall network determines the upper size limit for molecules that can penetrate and react with the interior of the wall. To obtain information concerning the accessibility of the porous cell wall of wood fibers, surfactant-templated sol-gel mineralization has been examined. Wood and kraft pulp samples of Norway spruce were impregnated with a silica sol-gel and subsequently heated (calcined) and transformed into structured mesoporous silica. Microscopy studies (environmental scanning electron microscopy, transmission electron microsopy, TEM) on the silica casts showed that the three-dimensional architecture of the wood and pulp fiber cell wall was revealed down to the nanometer level. Image analysis of TEM micrographs of silica fragments from the never-dried pulp revealed complete infiltration of the cell-wall voids and microcavities (mean pore width 4.7 ± 2 nm) by the sol-gel and the presence of cellulose fibrils with a width of 3.6 ± 1 nm. Cellulose fibrils of the same width as that shown by image analysis were also identified by nitrogen adsorption measurements of the pore size distribution in the replicas.
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| 9. |
- Pettersson, Torbjörn, et al.
(author)
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Leveling during toner fusing : Effects on surface roughness and gloss of printed paper
- 2006
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In: Journal of Imaging Science and Technology. - 1062-3701 .- 1943-3522. ; 50:2, s. 202-215
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Journal article (peer-reviewed)abstract
- The results of digital printing trials using a Xeikon press on uncoated and coated paper were analyzed using interferometric profilometry to characterize printed paper topography and toner film thickness. Solid print areas were fused at various temperatures, including radiant fusing with and without heated rolls. The overall surface roughness of the prints is slightly higher on the coated than uncoated paper, but is mainly dictated by transferred toner amount and fusing conditions. Increased toner coverage degree, or layer thickness, gives reduced surface roughness, provided the applied fusing power suffices. Increase in radiant fusing temperature yields a decrease in overall print roughness, however, this decrease is more pronounced on coated paper and higher toner amounts. Bandpass analysis of print surface roughness shows that short-scale roughness at or below the lateral length scales of toner particle dimensions always decreases with increasing radiant fusing temperature, whereas roughness contributions at wavelengths above 10 mu m can increase, with this transition value being shorter on coated paper and at lower toner amounts. Print gloss after radiant fusing is strongly correlated to print roughness on wavelengths up to this transition length scale, and the correlation can extend to order 100 mu m if complemented by heated roll fusing.
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| 10. |
- Pettersson, T, et al.
(author)
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Leveling during toner fusing: Effects on surface roughness and gloss of printed paper
- 2006
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In: Journal of Imaging Science and Technology. - 1062-3701 .- 1943-3522. ; 50, s. 202-215
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Journal article (peer-reviewed)abstract
- The results of digital printing trials using a Xeikon press on uncoated and coated paper were analyzed using interferometric profilometry to characterize printed paper topography and toner film thickness. Solid print areas were fused at various temperatures, including radiant fusing with and without heated rolls. The overall surface roughness of the prints is slightly higher on the coated than uncoated paper, but is mainly dictated by transferred toner amount and fusing conditions. Increased toner coverage degree, or layer thickness, gives reduced surface roughness, provided the applied fusing power suffices. Increase in radiant fusing temperature yields a decrease in overall print roughness, however this decrease is more pronounced on coated paper and higher toner amounts. Bandpass analysis of print surface roughness shows that short-scale roughness at or below the lateral length scales of toner particle dimensions always decreases with increasing radiant fusing temperature, whereas roughness contributions at wavelengths above 10 mm can increase, with this transition value being shorter on coated paper and at lower toner amounts. Print gloss after radiant fusing is strongly correlated to print roughness on wavelengths up to this transition length scale, and the correlation can extend to order 100 mm if complemented by heated roll fusing.
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