On the refractive index contrast modification in paper and printing applications : studies with fillers and coating pigments

dc.contributorAalto Universityen
dc.contributor.advisorGane, Patrick A.C., Prof.
dc.contributor.authorKoivunen, Kimmo
dc.contributor.departmentPuunjalostustekniikan laitosfi
dc.contributor.departmentDepartment of Forest Products Technologyen
dc.contributor.schoolKemian tekniikan korkeakoulufi
dc.contributor.supervisorPaulapuro, Hannu, Prof.
dc.description.abstractIn papermaking, fillers are traditionally added to the fibrous stock to extend expensive fibre, to improve the paper surface uniformity enabling beneficial liquid interactions during printing, and to improve the light scattering coefficient of paper. It is advantageous, therefore, to introduce as much filler as possible. However, fillers also have negative effects on paper properties, such as weakening the paper by preventing the formation of fibre-fibre bonds, which limit their use. Accordingly, fillers must be optimised to achieve the best functionality at controlled dose. One objective of the work is to improve paper optical properties, which could later promote more efficient use of materials in papermaking. Light scattering potential of fillers can be controlled by changes in the particle size distribution (PSD), specific surface area (SSA), shape, surface chemistry and refractive index (RI). Refractive index has received the least attention of these approaches. Therefore, novel fillers displaying increased effective refractive indices were developed. The results suggest that the methods studied can improve the light scattering effects. Since there are difficulties deconvoluting the boundary refractive index contrast from particle size in complex paper composites, which were highlighted in the first part, a second objective of the work was to study the complementary situation of reducing RI contrast by introducing liquid into a porous paper coating. The liquid distribution was then monitored by reflectance measurements. Knowledge of absorption behaviour of liquids into paper is essential for the print quality and controllability of printing processes. A relationship could be established, normalised for porosity, describing the reflectance change as a function of saturation level. In conclusion, the local change of refractive index boundary in a porous medium can be monitored indirectly via light scattering, or vice versa modified to affect scattering, and the opportunities for enhancing the function of filler-containing porous media can be identified. The combination of the publications and complementary results bound together in this work suggest that the methods studied provide potentially important new means to utilise RI contrast modification in papermaking and printing applications.en
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dc.identifier.isbn978-952-60-4034-9 (PDF)
dc.identifier.isbn978-952-60-4033-2 (printed)#8195;
dc.publisherAalto Universityen
dc.relation.haspart[Publication 1]: Kimmo Koivunen, Ilpo Niskanen, Kai-Erik Peiponen, and Hannu Paulapuro. 2009. Novel nanostructured PCC fillers. Journal of Materials Science, volume 44, number 2, pages 477-482.en
dc.relation.haspart[Publication 2]: Kimmo Koivunen and Hannu Paulapuro. 2010. Papermaking potential of novel structured PCC fillers with enhanced refractive index. TAPPI Journal, volume 9, number 1, pages 4-12.en
dc.relation.haspart[Publication 3]: Mikko Juuti, Kimmo Koivunen, Martti Silvennoinen, Hannu Paulapuro, and Kai-Erik Peiponen. 2009. Light scattering study from nanoparticle-coated pigments of paper. Colloids and Surfaces A: Physicochemical and Engineering Aspects, volume 352, numbers 1-3, pages 94-98.en
dc.relation.haspart[Publication 4]: K. Koivunen, H. Alatalo, P. Silenius, and H. Paulapuro. 2010. Starch granules spot-coated with aluminum silicate particles and their use as fillers for papermaking. Journal of Materials Science, volume 45, number 12, pages 3184-3189.en
dc.relation.haspart[Publication 5]: Lauri Kuutti, Kaisa Putkisto, Sari Hyvärinen, Soili Peltonen, Kimmo Koivunen, Hannu Paulapuro, Jere Tupala, Markku Leskelä, Tommi Virtanen, and Sirkka Liisa Maunu. 2010. Starch-hybrid fillers for paper. Nordic Pulp and Paper Research Journal, volume 25, number 1, pages 114-123.en
dc.relation.haspart[Publication 6]: P. A. C. Gane and K. Koivunen. 2010. Relating liquid location as a function of contact time within a porous coating structure to optical reflectance. Transport in Porous Media, volume 84, number 3, pages 587-603.en
dc.relation.haspart[Publication 7]: K. Koivunen and P. A. C. Gane. 2010. Optical reflectance as a function of liquid contact time and penetration depth distribution in coatings with mono and discretely bimodal pore size distributions. In: Proceedings of the 11th TAPPI Advanced Coating Fundamentals Symposium. Munich, Germany. 11-13 October 2010. Atlanta, Georgia, USA. TAPPI Press. Pages 108-128.en
dc.relation.ispartofseriesAalto University publication series DOCTORAL DISSERTATIONS , 11/2011en
dc.subject.keywordpaper optical propertiesen
dc.subject.keywordlight scattering coefficienten
dc.subject.keywordrefractive indexen
dc.subject.keywordcoating-liquid interactionen
dc.subject.otherPaper technology
dc.titleOn the refractive index contrast modification in paper and printing applications : studies with fillers and coating pigmentsen
dc.typeG5 Artikkeliväitöskirjafi
dc.type.ontasotVäitöskirja (artikkeli)fi
dc.type.ontasotDoctoral dissertation (article-based)en
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