Increased strength with multilayers on extensible kraft fibres

In this study high consistency refined pulp from an atmospheric and a pressurized refiner was low consistency refined in an Escher-Wyss laboratory refiner to a SR-number between 17,5-20,5. Ordinary ISO-sheets and freely dried sheets were manufactured from those pulp samples. The laboratory sheets made from pulp samples from the pressurized system had higher strain at break and tensile energy adsorption index but lower tensile index compared to sheets from the pulp sample refined in a conventional atmospheric high consistency system.

ISO-sheets and freely dried sheets were also made from refined pulp samples whose fibres had been coated with one or three layers of polymer. Polyelectrolyte multilayers were built by sequential provision of anionic starch and cationic CMC. Three different stock preparation strategies were used for the provision of polymer. Adsorption equilibrium was determined indirectly by charge titration of non-adsorbed polyelectrolyte in a particle charge detector. Physical paper properties of the sheets showed that the addition of only one layer of starch increased strain at break, tensile index, tensile energy adsorption index and Scott-Bond significantly. By using the multilayer technique tensile index could be increased further compared to sheets from fibres with one single starch layer, however, no major positive effects on strain at break and tensile energy adsorption index was obtained. When the fibres were treated with multilayers Scott-Bond, which is a measure of the internal bonding strength, increased dramatically compared to the samples with one layer of starch.

Author: Averheim, Andreas

Source: LuleƄ University of Technology

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