In the flow distribution section of a paper machine, known as the head box, water is injected into the fiber suspension (stock) flow through a tee-mixer for more uniform production. This dilution process has two important requirements that must be fulfilled: (1) sufficient mixing so that the dilution flow spreads across the suspension flow and (2) that the injection flow rate not be so large to significantly alter the local head box flow rate. The objective of this research was to find a combination of velocity ratio and tee mixer geometry that lead to the injection flow being well mixed into the stock flow, but at the same time, the injection should not cause the total flow rate to change by more than 1%. Velocity ratios of 0.25, 0.75, 1.33, 1.5 and 2.25 were examined for four different cases of tee mixer geometries using the CFD software Fluent. Two of the cases had added contractions located near the injection point, while the other two cases had a more standard geometry with no added complexities. The pressure drop across the injection point was also measured. Mixing was qualitatively measured by simulating the injection of a passive tracer into the dilution flow. All of the results indicated that the case where the contraction was located after the injection showed the most promising results with quality mixing and lower flow rates. The cases without added contractions showed poor mixing for lower velocity ratios, and for higher velocity ratios, the flow rates were too large. The cases with contractions showed similar mixing, but the outlet flow rates produced were lower when the contraction was located after the injection instead of before it. A velocity ratio of 0.25-0.75 for the mixers with contractions produced acceptable flow rates and sufficient mixing. The simulations also showed that the static pressure for the contraction cases were nearly identical throughout the majority of the pipe. For both contraction cases the pressure drop across the injection increased with increasing injection flow rate. When the contraction was located before the injection, a pressure drop of 16% was calculated. A pressure drop of 18% to 20% across the injection resulted when the contraction was located after the injection.

As a low cost natural polymer, starch is widely used in paper, food, adhesive, and many other industries. In order to improve the performance of starch, crosslinking is often conducted either in the processes of starch modification or during the application processes. Many crosslinkers have been developed in the past for crosslinking starch. Ammonium zirconium carbonate (AZC) is one of the common crosslinkers for crosslinking starch in aqueous solutions, having been widely used as a starch crosslinking agent in paper surface coating for more than 20 years. However, the mechanisms of starch crosslinking with AZC have not been well studied. In order to optimize the crosslinking chemistry of starch and find new paths for the utilization of starch in papermaking, a better understanding of the starch crosslinking mechanism is necessary. This thesis focuses on the fundamental study of starch crosslinking in an aqueous solution and its applications in fiber surface grafting, filler modification, and starch nanoparticle formation. Particularly, the thesis contains three major parts: (1) Mechanism study of starch crosslinking induced by AZC: In this thesis, the crosslinking (or gelation) kinetics of starch/AZC blends were investigated by using rheological measurements. The evolution of viscoelastic properties of AZC solutions and the AZC-starch blends was characterized. It was found that for both AZC self-crosslinking and AZC-starch co-crosslinking, the initial bond formation rate and the gel strength had a strong power law relationship with the concentrations of both AZC and starch. It is suggested that the development of the crosslinking network is highly dependent on the AZC concentration, while the starch concentration effect is less significant. It was determined that the activation energy of AZC self-crosslinking was approximately 145-151 kJ/mol, while the activation energy of AZC-starch co-crosslinking was 139 kJ/mol. (2) Fiber and filler modifications with starch and crosslinkers: Besides reacting with starch, AZC can react with cellulose which also contains hydroxyl groups. Theoretically, it is possible to use AZC as a crosslinker / coupling agent to graft starch onto cellulose fibers. It is believed that the grafted starch on fiber surfaces can improve the fiber bonding capability. In this thesis, a facile method to graft starch onto cellulose fiber surfaces through the hydrogen bond formation among cellulose, starch and AZC was developed. Compared with the paper sheets made of fibers with an industry refining level (420 ml CSF), the paper sheets made of fibers with a much lower refining degree but with grafted starch showed higher paper strengths, including the tensile strength, stiffness and z direction tensile; meanwhile, a faster drainage rate during web formation could also be achieved. Not only can the fiber-fiber bonding be improved by grafting starch onto fiber surfaces, but the filler-fiber bonding can also be improved if starch can be effectively coated on the filler surface. This concept has been supported by the early studies. In this thesis, the effects of the crosslinking of starch in the filler modification for the papermaking application were also studied. (3) Mechanism of starch nanoparticle formation during extrusion with crosslinkers: It was reported that starch crosslinking could facilitate the reduction of starch particle size during reactive extrusion. However, the mechanism of the particle size reduction by starch crosslinking was not illustrated. The reason that the crosslinking can cause the particle size reduction of starch during extrusion is fundamentally interesting. In this thesis, the mechanism of starch particle size reduction during extrusion with and without crosslinkers was investigated by identifying the contributions of thermal and mechanical effects. The effects of extrusion conditions, including temperature, screw speed, torque, starch water content and crosslinker addition, on the particle size were studied. It was found that the addition of crosslinkers could significantly increase the shear force (torque), and consequently facilitate the reduction of the particle size. The results indicate that for extrusion without a crosslinker, the starch particle size decreased with the increase of temperature. At 100 degree Celsius, the starch particles with a size of 300 nm could be obtained. With the addition of appropriate crosslinkers (glyoxal), the starch particle size could be reduced to around 160 nm, even at a lower extrusion temperature of 75 degree Celsius .

<p>The orientation of fibres suspended in a viscous fluid, flowing over a solid surface, has been studied experimentally. A shear layer was generated, by letting the suspension flow down an inclined plate. Far upstream from the measuring section the suspension was accelerated to obtain an initial orientation of the fibres aligned with the flow direction. A CCD-camera was used to visualise the fibres. The velocity profile of the fibres coincided with the theoretical expression for fully developed flow of Newtonian liquid down an inclined wall.</p><p>The orientation of the fibres was analysed in planes parallel to the solid surface. At distances from the wall larger than one fibre length the fibres performed a tumbling motion in the flow-gradient plane in what appeared to be Jeffery-like orbits. Closer to the wall a difference was found between fibres of aspect ratio <i>r</i><i>p </i>= 10 and 40. The longer fibres of <i>r</i><i>p </i>= 40 kept their orientation, aligned with the flow, also in the near wall region. For the shorter fibres the orientation shifted gradually, to orientations closer to the vorticity axis, when the distance from the wall was decreased. In the very proximity to the wall the fibres were aligned with the vorticity, perpendicular to the direction of the flow. Another distinction, most likely related to the fibre orientation, was seen in the wall normal concentration profile. Due to sedimentation effects fibres accumulated in the near wall region. For fibres of <i>r</i><i>p </i>= 10 a peak in concentration was found at the wall, while for r=40 the maximum concentration was found approximately half a fibre length from the wall. It is previously known that a fibre can interact with the wall in what is referred to as a "pole vaulting" motion away from the wall. It is suggested, as a likely explanation to the location of the maximum concentration, that fibres of <i>r</i><i>p </i>= 40 perform this motion, while fibres of <i>rp</i>=10 do not.</p><p>In another experiment the surface of the wall was modified with ridges. For fibres of <i>r</i><i>p </i>= 10 there were no longer any fibres oriented perpendicular to the flow direction in the near wall region.</p><p>The main application in mind throughout this work is papermaking. The study is considered to be of fundamental character and is not applicable in a direct sense. The difference between the flow situation in the experiments and the paper machine is discussed further.</p>

Thesis (Ph. D.)--Institute of Paper Chemistry, 1951. / Includes bibliographical references (p. 117-119).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1943. / Includes bibliographical references (p. 84-85).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1940. / Includes bibliographical references (leaves 113-117).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1934. / Includes bibliographical references (leaves 48-51).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1975. / Bibliography: leaves 101-103.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1941. / Bibliography: leaves 64-65.

Background: The bleaching of paper is an important and controversial treatment employed in the conservation of art. The use of a bleach may greatly enhance the quality of an image but at a cost of lost structural integrity. In order to fully consider the ramifications of bleaching a paper artifact, a historical study of early European paper and its manufacture was conducted. The structure of paper was also studied in order to understand the finer points of early European paper manufacture and to draw conclusions from the bleaching comparison. Results: A comparison of the commonly used ClO2 bleaching with a previously proposed chlorous acid treatment was conducted. The two different bleaching techniques were evaluated on their impact on the colour of artificially aged and unaged Whatman chromatography 1 paper. The results of the bleaching were analyzed with a colourimeter and it was determined that there was a significant change in colour as a result of the bleaching. The ClO2 and chlorous acid bleaching treatments did not produce results that were significantly different from one another, visually and statistically. The bleaching treatments were also tested with the viscometry of the paper in cadoxen and it was determined that ClO2 is a more degradative bleach than chlorous acid. The research also demonstrated that bleaching has a greater degradative impact on previously degraded samples. The quantitative results of the viscometry were accompanied by a qualitative look at the paper samples with a scanning electron microscope (SEM). In the SEM images there were slight visible differences in the samples that could correlate to aging. Conclusions: Chlorous acid is a gentle effective bleaching technique that was as effective as ClO2 and less degrading to the paper samples. Bleaching has an increased impact on previously degraded samples, and conservators should be wary of this. Further research involving this bleaching technique is suggested. The use of an SEM in imaging damage to paper is a viable option but more work is needed with this technique to ensure conclusive results. / Thesis (Master, Art History) -- Queen's University, 2012-01-31 22:51:58.027