[lic] Kemian tekniikan korkeakoulu / CHEM

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Browsing [lic] Kemian tekniikan korkeakoulu / CHEM by Subject "accessibility"

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  • Viscose filterability and fiber wall pore size as a measure of pulp reactivity
    (2019) Lehtonen, Eeva
     School of Chemical Engineering | Licentiate thesis
    This study presents research on pulp properties and characteristics affecting the reactivity and accessibility of the pulps. Pulps with different production methods and wood species were selected for the tests. Mainly dissolving pulps were investigated, but in addition, one paper grade pulp was also included in the selection as a reference of hemicellulose-rich pulp. In order to comprehensively understand the cellulose structure, pulp samples were investigated at three different levels: molecular, supramolecular and morphological. The main method used in this study was the viscose filterability test (Treiber test), which determines the filterability value (FV) of viscose and describes pulp reactivity, which is understood as the processability and quality of the pulp. The Treiber test device was built and thoroughly evaluated for FV determination. Pulp accessibility (reactivity) was investigated by determining the pore size of the fibre wall. The methods included solid-state NMR (to determine the lateral fibril aggregate dimensions (LFAD)), the fibre saturation point (FSP) and BET measurements. The results showed that the production method of the dissolving pulp, as well as pulp’s chemical composition, macromolecular properties and other characteristics affect the pulp reactivity (FV). High hemicellulose content indicated poor reactivity (FV) and a lower CS2 -charge negatively affected reactivity. A relationship between the crystallinities measured by NMR and the viscose filterability was found. This result was not expected, due to the results of earlier studies. A correlation between the crystal width and the filterability value was also found. Viscose filterability increased parallel with increasing crystal width.