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Towards an understanding in paper strength
2002 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

It is argued that currently available strength models for paper are incapable of accurate predictions of strength behaviour. This is because these models fail to characterise the fibre material uniformly. A novel approach to paper strength developed by W. Batchelor is described in this thesis report. The new theory models a sheet of paper as a regular matrix of rectangles that wholly enclose the shape of a fibre cross-section. A formula can be derived from the new theory, which relates the relative bonded area in a sheet of paper (ie. the bonding degree) to the fill factor , the apparent sheet density and the density of the fibre material. The aim of this work was to verify and modify the new theory of paper strength by carrying out hydrocyclone fractionation and wet pressing experiments, then measuring the fibre and paper properties listed above. A confocal laser-scanning microscope was utilised to analyse the paper structure using a new microscopical technique developed by H. Jihong. The confocal microscope was also useful when analysing the degree of separation in the hydrocyclone. The major result of this thesis work was the successful fractionation of a softwood kraft pulp in a single hydrocyclone, due to the apparent density factor of the fibres. Hand sheets from the fractionated pulp were produced under different wet pressures and it was found that the hand sheets differ in apparent density, brightness and strength due to the pressing level as well as to the fraction that the pulp in the hand sheets originates from. The new theory developed by W. Batchelor could not be completely verified due to problems with the measurements of the relative bonded area. The model verification can only then be carried out once these data is available and a step towards an understanding in paper strength will then be made.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Tensile strength, fractionation, paper
Keyword [sv]
URN: urn:nbn:se:ltu:diva-51881ISRN: LTU-EX--02/023--SELocal ID: 90ee040d-e2bb-4183-b1ff-914bfd78c864OAI: diva2:1025245
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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