Nitrogen, argon and oxygen adsorption isotherms at 78 °K have been determined on samples of solvent exchange dried, fully bleached, kraft pulp of western hemlock and Douglas fir. The solvent exchange drying sequence used was water-methanol-n-pentane with the n-pentane removed at room temperature. The pulp samples were in two groups: one group was beaten to various levels on a P.F.I. mill and solvent exchange dried from a water swollen state; the second group was air dried to different moisture contents and then solvent exchange dried. The presence of micropores (Dubinin definition) in solvent exchange dried cellulose has been shown. This finding was suggested by the results of Harris, who noted that adsorbents having an average pore radius of less than 18 Å indicated an average Kelvin pore radius of 18 Å. The finding of micropores in solvent exchange dried cellulose was substantiated by the pore volume distribution which indicated a very large volume of pores at 18 Å radius, and by the Dubinin plot technique for the measurement of micropore volume. Some solvent exchange dried wood pulp samples indicated that up to 70 percent of their total pore volume was present as micropores. The presence of micropores with the associated enhanced adsorption and restricted adsorption space complicates the analysis of isotherms so that the B. E. T. surface area and Kelvin type pore analysis cannot be considered reliable. An investigation into the effects of errors associated with assuming values for the physical properties of adsorbed molecules led to the conclusion that gas adsorption is useful for indicating trends or for use as a parameter for correlations of some pulp and paper properties but should not be used to postulate models of specified dimensions. The Kelvin type pore analysis and the Dubinin pore analysis have been shown to be very sensitive to the model assumed to describe the physical structure.of the wood pulp fibre. While gas adsorption techniques are of doubtful validity for solvent exchange dried pulp samples, the B.E.T. analysis, was found to be quite reliable on air dried paper sheets. The existence of the large volume of pores of approximately 18 Å radius (cylindrical pore model) or 25 Å wall separation (parallel sided fissure model) in solvent exchange dried cellulosic materials which have been found by other workers has been shown to be doubtful. This finding is substantiated by the accessibility data of Stone and Scallan which does not indicate a large volume of pores near the most common pore sizes found by gas adsorption. P. F. I. mill beating of the pulp was found to lower the surface area slightly, to shift the pore size distribution slightly to larger pore sizes and to substantially lower the volume of pores at the most common pore size. The Dubinin micropore volume analysis also indicated lowering of micropore volume with beating. These results led to the conclusion that beating affected the structure of the pulp fibre even in structural elements of the smallest size measured. Partial drying of the pulp handsheets prior to solvent exchange drying was found to lower the surface area by nearly two orders of magnitude and to shift the pore volume distribution strongly to the smaller pore sizes. The effects of .beating and drying were easily interpreted on the basis of the Stone and Scallan parallel sided fissure model of the structure of cellulose. Comparisons between isotherm shapes indicated solvent exchange dried wood pulp may have a structure similar to montmorillonite, which is known to have a flat plate structure. The Kaganer and "t"-plot analytical techniques were applied to the solvent exchange dried wood pulp as additional methods of obtaining estimates of the surface area. The surface areas determined by these methods were significantly larger than those found by the B. E. T. equation, however, the trends were found to be the same. Handsheets were made from the pulp samples and these sheets were subjected to physical tests. The surface areas of these sheets were determined and the bonded areas estimated. The bonded area was found to increase with the level of beating. Sheet density increased as bonded area increased, so did the breaking length and burst. Tear factor decreased as the bonded area increased. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Ph.D. / The main objective of this study was to investigate the presence, variations and the fate of lipophilic extractives during all the stages in the dissolving pulp production process. Lipophilic wood extractives which include fatty acids, sterols, hydrocarbons, steroid hydrocarbons and ketones are organic compounds present in the wood and dissolving pulp which are soluble in organic solvents. Their presence in wood and pulp has negative effects on both the pulping process and the quality of the produced dissolving pulp. Comparison of two Eucalyptus species (E. grandis and E. dunnii) at three different sites (Richmond, Umvoti and Ixopo in KwaZulu-Natal Province, South Africa) revealed that lipophilic extractives were higher in E. dunnii than in E. grandis in all the sampled sites and that the woods at the Ixopo site were found to have the highest amount of lipophilic extractives. The quantitative variation of lipophilic extractives in wood was found to be significantly affected by respective sites and tree species. The principal component analysis (PCA) model, which was used to correlate soil parameters and amount of lipophilic extractives in woods per each site, revealed that high amounts of lipophilic extractives were found in trees grown at sites with a high composition of clay soil and organic matter. Thus if the industry is to avoid the high levels of lipophilic extractives in wood, sandy sites should be the choice to grow the trees. Partial least squares (PLS) modelling revealed that sterols and saturated fatty acids significantly influence the quality parameters (Kappa number, viscosity, copper number, cellulose yield and retained carbohydrates) of dissolving pulp, whereas unsaturated fatty acids and unsaturated sterols in particular were found to positively correlate with the Kappa number, thus affecting its measurement.The main objective of this study was to investigate the presence, variations and the fate of lipophilic extractives during all the stages in the dissolving pulp production process. Lipophilic wood extractives which include fatty acids, sterols, hydrocarbons, steroid hydrocarbons and ketones are organic compounds present in the wood and dissolving pulp which are soluble in organic solvents. Their presence in wood and pulp has negative effects on both the pulping process and the quality of the produced dissolving pulp. Comparison of two Eucalyptus species (E. grandis and E. dunnii) at three different sites (Richmond, Umvoti and Ixopo in KwaZulu-Natal Province, South Africa) revealed that lipophilic extractives were higher in E. dunnii than in E. grandis in all the sampled sites and that the woods at the Ixopo site were found to have the highest amount of lipophilic extractives. The quantitative variation of lipophilic extractives in wood was found to be significantly affected by respective sites and tree species. The principal component analysis (PCA) model, which was used to correlate soil parameters and amount of lipophilic extractives in woods per each site, revealed that high amounts of lipophilic extractives were found in trees grown at sites with a high composition of clay soil and organic matter. Thus if the industry is to avoid the high levels of lipophilic extractives in wood, sandy sites should be the choice to grow the trees. Partial least squares (PLS) modelling revealed that sterols and saturated fatty acids significantly influence the quality parameters (Kappa number, viscosity, copper number, cellulose yield and retained carbohydrates) of dissolving pulp, whereas unsaturated fatty acids and unsaturated sterols in particular were found to positively correlate with the Kappa number, thus affecting its measurement. Viscosity of pulp which is an important quality parameter was also found to be positively influenced by sterol residues, whereas the reducing properties of pulp were found to be affected by sterols and saturated fatty acids with a carbon chain length of less than C20.

A new technique for measuring the water content of fiber is presented. Tritiated water is added to a pulp/water suspension whereupon the tritium partitions between the bulk water and the pulp. Through this technique a fiber:water partition coefficient is developed, Kpw. This thesis will cover the development of the Kpw procedure and three different case studies. The first study involves comparing Kpw to traditional methods of fiber water content. The procedure provides a value of ten percent for the tightly bound water content of unrefined hardwood or softwood kraft fiber, either bleached or unbleached. If this water is assumed to cover the fiber surface as a monolayer, then an estimate of the wet surface area of fiber can be obtained. This estimate compares well to independent measurements of surface area. Kpw has also been found to be valuable in furthering the understanding of refining. Based on the study, it is proposed that refining occurs in three discrete stages. First, refining removes the primary cell wall and S1 layer while beginning to swell the S2 layer. Next, internal delamination occurs within the S2 layer. Finally, fiber destruction occurs at high refining levels. By using Kpw, the three stages of refining are clearly recognized. Lastly, Kpw is used to study the effect of hornification on bleached softwood kraft fiber. The recycling effects at three refining levels were characterized by Kpw and followed closely the findings of the refining study. At low and high refining levels, the impact of recycling was minimal according to Kpw results, but at 400 mL csf the impact of recycling was much more pronounced. This could be attributed to the closing of internal delaminations within the fiber.

The scope of these studies was two-fold: to evaluate high pressure homogenized slurries as a rapid means of screening wood pulps for their Cu, Mn and Fe content and to evaluate the high pressure homogenization in combination with chelating agents or enzymatic digestion for the liberation/extraction of metal ions from this matrix. / Cu, Mn and Fe were determined successfully in pulp samples using high-pressure homogenization prior to slurry introduction-GF-AAS. The analysis time of the method from sample acquisition to determination was of the order of a few minutes per sample. / Different cellulose swelling/dissolution agents were evaluated for the generation of quasi-stable pulp suspensions, rich in cellulose. High-pressure homogenization alone or in combination with chelating agents or enzymatic digestion was also investigated as a means of quantitatively releasing these metal ions into the liquid phases. / A new model of homogenizer equipped with ceramic homogenizing valve with a few modifications was evaluated in terms of metal contamination levels within the final sample dispersion. (Abstract shortened by UMI.)

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