The Effect of Silica Surface Area on Microparticle Retention Systems

Retention of fines and fillers has always been a concern in the paper industry. There has been many different types of retention aids in the past, but they lack performance under the vigorous conditions in today\u27s paper mills. High shear forces associated with high speed paper of recycled materials into the mill brought along with it high fines content and a lot of anionic trash which readily reacts with cationic polymers. Consequently, the dosage must be increased which can lead to poor formation and increased chemical cost. A new retention aid was needed to combat these problems. Microparticle retention systems were developed by a group of papermakers, scientist, and process control experts in the late 1970\u27s. A dramatic improvement in retention and drainage was achieved, which allowed higher filler loading, increased machine speeds, and better formation. To this date, continuing research is being done on the improvement of microparticle retention aids as well as developing new retention aids. This paper deals with microparticle retention systems in a different way. Normally, the dosage of microparticle, anionic silica in this research, to the system is on a weight basis, i.e., pounds of microparticle per ton of paper. In this study, silica dosage will be done on a surface area basis. Silica particles have a very high specific surface area, which can range anywhere from around 500m2/g to 1200m2/g. Using this information and the typical dosage rate on a weight basis, a surface area dosage can be calculated. For example, 600m2/g X 1.0 lb./ton = 272,155m2/ton and 1200m2/g X 0.5lb./ton X 272,155m2/ton . Both give the same surface area dosage, but different only half of the weight basis dosage is needed for the high surface area silica. Therefore, the objective of this thesis is to test the hypothesis that equivalent retention will be obtained when equal surface area dosage is applied to the system. A two level, three variable factorial design was used to test the effects of surface area of microparticle, surface area dosage, and polymer dosage. Two different furnishes were used, a fine paper grade and a wood containing grade. Both grades are similar to those found in industry. All retention studies were carried out using a Britt Dynamic Drainage Jar. Percent fines and ash retention was measured. The results for the fine paper furnish showed no conclusive trends other than an effect of polymer dosage on fines retention. The variability in the system was extremely high. The wood containing furnish, however showed several promising results. Again, the polymer dosage was found to have a large effect on the system. There was an interaction between surface area dosage and polymer dosage. At low polymer dosages, the surface area dosage had an effect on retention, but at high polymer dosage, there was not an improved retention response as the surface area dosage increased. Finally, the wood containing furnish followed the hypothesis that equivalent retention will be obtained at equal surface area dosage. Many chemical suppliers pride themselves on the high surface area of their microparticle and the improved performance it offers. The results of this thesis show that this may not be exactly true. The dosage needed to get the same retention with a high surface area microparticle may be less, but not necessarily improved performance. If retention could be measured as a function of surface area added to the system per ton of paper, a mill could determine what is the most economical microparticle to use. For example, a supplier could supply a low surface area microparticle at a very low price, while the another supplier is offering a high surface area microparticle at an extremely high price. The mill would have to use a lot more of the low surface area microparticle to get the retention they want, but it sill may be more economical

Wave-number dependence of the transitions between traveling and standing vortex waves and their mixed states in the Taylor-Couette system

Previous numerical investigations of the stability and bifurcation properties of different nonlinear combination structures of spiral vortices in a counterrotating Taylor-Couette system that were done for fixed axial wavelengths are supplemented by exploring the dependence of the vortex phenomena waves on their wavelength. This yields information about the experimental and numerical accessability of the various bifurcation scenarios. Also backwards bifurcating standing waves with oscillating amplitudes of the constituent traveling waves are found.Comment: 4 pages, 5 figure

A study of the factors affecting boundary layer two-dimensionality in wind tunnels

The effect of screens, honeycombs, and centrifugal blowers on the two-dimensionality of a boundary layer on the test section floors of low-speed blower tunnels is studied. Surveys of the spanwise variation in surface shear stress in three blower tunnels revealed that the main component responsible for altering the spanwise properties of the test section boundary layer was the last screen, thus confirming previous findings. It was further confirmed that a screen with varying open-area ratio, produced an unstable flow. However, contrary to popular belief, it was also found that for given incoming conditions and a screen free of imperfections, its open-area ratio alone was not enough to describe its performance. The effect of other geometric parameters such as the type of screen, honeycomb, and blower were investigated. In addition, the effect of the order of components in the settling chamber, and of wire Reynolds number were also studied

The 100 micron surveys in the Northern and Southern Hemispheres

Partial surveys in the far infrared in the Northern and Southern Hemispheres have covered 40% of the galactic equator and assorted regions away from the galactic plane. Approximately 120 100-micron objects are known. These are distributed extensively in galactic longitude and concentrated within + or - two degrees in galactic latitude. From this information, some general conclusions can be drawn about the sensitivity and coverage required for a general sky survey in the far infrared

Sapphire planar waveguides fabricated by H+ ion beam implantation

1.1-MeV proton-implanted sapphire waveguides are investigated for the first time. Optical measurements show that the planar waveguides support low-order transverse-mode propagation with good guiding properties without the need to anneal the samples

Proton implanted sapphire planar and channel waveguides

We report low-order transverse-mode planar waveguides in sapphire fabricated for the first time by proton implantation. The waveguides show good guiding properties without post-implantation annealing. Channel waveguiding was achieved by polyimide strip-loading

Structuring of sapphire by laser-assisted methods, ion-beam implantation, and chemical wet etching

Sapphire is an attractive material for micro- and opto-electronic systems applications because of its excellent mechanical and chemical properties. However, because of its hardness, sapphire is difficult to machine. Titanium-doped sapphire is a well-known broadly tunable and short-pulse laser material and a promising broadband light source for applications in low-coherence interferometry. We investigated several methods to fabricate rib structures in sapphire that can induce channel waveguiding in Ti:sapphire planar waveguides. These methods include direct laser ablation, laser-micromachined polyimide stripes, selective reactive ion etching, and ion-beam implantation followed by chemical wet etching. Depending on the method, we fabricated channels with depths of up to 1.5 µm. We will discuss and compare these methods. Reactive ion etching through laser-structured polyimide contact-masks has so far provided the best results in terms of etching speed and roughness of the etched structures