On the Network Strength of Meta-Aramid Fiber Suspension and Its Relationship to Formation

Because of poor surface hydrophilicity, meta-aramid fibers readily form flocs by intertwining or interlacing, and this severely affects the uniformity of meta-aramid paper. To investigate the flocculation mechanism of meta-aramid fiber suspensions, the critical flocculant concentration, shear, and compressive network strength of meta-aramid fiber suspensions were examined. A hand sheet former was used to study the influence of the yielding properties of suspensions on the uniformity of meta-aramid paper, and the relationship between the formation index and rheological properties was determined. The results showed that the critical gel concentration ranged from 0.37 to 0.68 g/L, which was much lower than that of plant fiber suspensions. In addition, the compressive yield stress ( P y ) and shear yield stress ( τ y ) of the meta-aramid fiber suspensions were found to increase linearly and exponentially, respectively, with an increasing concentration, and the uniformity index of the paper sheets was found to depend on a power of τ y ⋅ P y . This provides an effective method for predicting paper sheet uniformity.

Measurements of Magnetic Fiber Dynamics in Magnetic Fields using Optical and Electrical Techniques

<p>The fabrication of piezoelectric ceramics (Piezoceramics) currently relies on a costly dice and fill process to create an array of aligned pillars. These pillars act as waveguides, improving the performance of the piezoceramic wafers over the bulk piezoceramic alone. It is theorised the creation of aligned pores in the piezoceramic may exhibit the same waveguiding effect, removing the need for the dice and fill process. A technique for creating these pores is in development at Callaghan Innovation, New Zealand, where nickel coated carbon fibers are added to the ceramic slurry, aligned with a magnetic field, and attracted to the bottom of a mold. The number of fibers and degree of alignment dictate the waveguiding effectiveness and hence the performance of the piezoceramic. Additionally the time taken for fibers to form an array in the bottom of the mold dictate the piezoceramics fabrication time. Thus it is crucial to be able to measure the alignment and magnetically assisted sedimentation of these fibers in-situ. However the ceramic slurry is opaque, hence the optical methods traditionally can not be implemented. This thesis describes the development and implementation of an electrical technique using the anisotropic conductance of fibers, for measuring fiber dynamics during the fabrication of piezoceramics. The results of this electrical technique are compared to both optical monitoring results in a transparent solution, and models for the motion of rigid cylinders in a fluid suspension. The change in conductance corresponding to fiber rotation was found to have a time constant corresponding to fiber rotation which is a scalar multiple of that of transmission microscopy and the mathematical modeling. This is a product of the geometry of the electrode configurations used to measure conductance. Furthermore, for fiber rotation, the fiber concentration in the solution changes the effective fluid viscosity due to hydrodynamic turbulence created by the rotating fibers. The conductance change corresponding to the magnetically assisted fiber settling is in good accordance with both the optical observations and mathematical modeling for 50 mPas solutions, however for 30 mPas solutions the modeling underestimates the settling time by 20%. The maximum fiber concentration to create a single layer of aligned fibers in the bottom of the mold was found to be 12 fibers=mm³. Exceeding this limit results in a secondary and tertiary layer of fibers forming directly below the fiber suspension injection location.</p>

Measurements of Magnetic Fiber Dynamics in Magnetic Fields using Optical and Electrical Techniques

<p>The fabrication of piezoelectric ceramics (Piezoceramics) currently relies on a costly dice and fill process to create an array of aligned pillars. These pillars act as waveguides, improving the performance of the piezoceramic wafers over the bulk piezoceramic alone. It is theorised the creation of aligned pores in the piezoceramic may exhibit the same waveguiding effect, removing the need for the dice and fill process. A technique for creating these pores is in development at Callaghan Innovation, New Zealand, where nickel coated carbon fibers are added to the ceramic slurry, aligned with a magnetic field, and attracted to the bottom of a mold. The number of fibers and degree of alignment dictate the waveguiding effectiveness and hence the performance of the piezoceramic. Additionally the time taken for fibers to form an array in the bottom of the mold dictate the piezoceramics fabrication time. Thus it is crucial to be able to measure the alignment and magnetically assisted sedimentation of these fibers in-situ. However the ceramic slurry is opaque, hence the optical methods traditionally can not be implemented. This thesis describes the development and implementation of an electrical technique using the anisotropic conductance of fibers, for measuring fiber dynamics during the fabrication of piezoceramics. The results of this electrical technique are compared to both optical monitoring results in a transparent solution, and models for the motion of rigid cylinders in a fluid suspension. The change in conductance corresponding to fiber rotation was found to have a time constant corresponding to fiber rotation which is a scalar multiple of that of transmission microscopy and the mathematical modeling. This is a product of the geometry of the electrode configurations used to measure conductance. Furthermore, for fiber rotation, the fiber concentration in the solution changes the effective fluid viscosity due to hydrodynamic turbulence created by the rotating fibers. The conductance change corresponding to the magnetically assisted fiber settling is in good accordance with both the optical observations and mathematical modeling for 50 mPas solutions, however for 30 mPas solutions the modeling underestimates the settling time by 20%. The maximum fiber concentration to create a single layer of aligned fibers in the bottom of the mold was found to be 12 fibers=mm³. Exceeding this limit results in a secondary and tertiary layer of fibers forming directly below the fiber suspension injection location.</p>

Method for milk whey microfiltration with filtrate pulsed backpressure and installation for its implementation

During deep processing of whey using microfiltration, the loss of membrane efficiency can take place. In this work, an installation for microfiltration of milk whey has been developed. It includes pumps, containers with liquids, throttling valves, a pressure gauge, and a microfiltration cell with a tubular ceramic membrane. A thin titanium oxide layer was deposited on the inner surface of the porous alumina tube. The outer diameter of the tubes is 10 mm, the wall thickness is 2 mm, the length of the tubes is 45 cm. A homogenized aqueous dispersion of sugar beet fiber was used as an agent that improves the performance of the installation by creating a pulsed backpressure of the filtrate. It is shown that the use of a finely ground suspension of dietary fiber during microfiltration of milk whey through a tubular ceramic membrane prevents the formation of protein deposits on the membrane and in its pores. The installation allows obtaining a suspension of dietary fiber, enriched with milk protein, as an additional product. The protein-enriched fiber suspension left over after microfiltration can be used in food production, for example, as a thickening agent in the production of yogurts.

Eucalyptus Pulp Fibers with In-Situ Precipitated Calcium Carbonate – A 12-Inch Laboratory Paper Machine Study

Paper manufacturing on a global scale is a highly competitive market which requires to constantly improve the manufacturing process to be competitive. To decrease production cost paper manufactures, add filler material prior to sheet forming to replace costly wood fiber based raw material. This research project investigates the use of in-situ precipitated calcium carbonate produced in the presence of eucalyptus fiber material at a 41.0% filler level prior to beating. The in-situ filler containing eucalyptus fiber suspension was used on a 12’ (304mm) wide Laboratory Fourdrinier Paper Machine together with non-filler containing eucalyptus fiber material, and a commercial precipitated calcium carbonate filler material. The manufactured in-situ fiber suspension resulted in a higher ash retention compared to the addition of the powdered commercial PCC filler material. In addition to commercial filler material retention is improved at higher filler addition above 30%. The increased ash retention is linked to the increased micro fibrillation fiber material of the in-situ filler-fiber suspension forming neckless like particles on the fibers microfibrils. Mechanical paper properties showed an improvement for in-situ precipitated filler material compared to commercial filler material addition. Optical properties could be improved in comparison to the eucalyptus fiber without filler addition for in-situ precipitated filler material and a combination of in-situ and commercial filler material.

Numerical analysis of multiphase flow of couple stress fluid thermally effected by moving surface

The study of multiphase flows gained much importance because of its extensive applications in nature and industry. These flows possess two or more thermodynamic phases, for example, one component phase (e.g., water vapors and water flow) or several components phase (e.g., water and oil flow). The most common example of multiphase flow in the context of the oil industry is petroleum. Further blood flow, porous structures, fluidized bed, bubbly flow in nuclear reactors, and fiber suspension in the paper industry are some significant examples of multiphase flows. In this paper, we considered the Couette flow of non-Newtonian (couple stress) fluid with variable magnetic field and thermal conductivity effects between parallel walls of the channel. The upper wall of the channel is in constant motion while the lower wall is in a fixed position. The variable viscosity effects with the suspension of hafnium particles are also discussed by taking Vogel’s viscosity case. The shooting method based on the R–K method is applied to obtain the numerical solution of the current problem. A comparison between Newtonian and non-Newtonian fluids is presented by sketching graphs. The variations in flow and temperature of fluid against various involved factors, including variable viscosity, wall temperature, thermal radiations, variable magnetic field, and thermal conductivity are sketched and also physically described. It is observed that variable viscosity parameter elevated both velocity and temperature profiles while wall temperature parameter decelerated both fields. Further, noticed that the variable thermal conductivity and variable magnetic field impede the velocity of the fluid and also retarded the temperature field. Our attempt is not just useful to investigate the mechanical and industrial multiphase flows but also delivers important results to fill the gap in the existing literature.

In Situ Precipitated Calcium Carbonate in the Presence of Pulp Fibers – A Beating Study

The paper industry around the world is in search for new ways to decrease production costs. New approached with additives such as new developed In Situ precipitated paper fillers materials have the potential to reduce production cost and increase profit margins. In Situ precipitated calcium carbonate filler with 20.9% and 41.7% filler material was produced in a large-scale laboratory unit using a eucalyptus pulp fiber suspension with a 1.7% fiber solids content. Laboratory beating tests were performed with a Valley Beater and APFI Mill using pure eucalyptus pulp with no filler content as the based trial and the two-laboratory manufactured In Situ precipitated filler pulps. Valley Beater and PFI Mill laboratory beating machines show similar differences/trends for the breaking length, tear and burst index. EC-pulp with no filler has the highest strength for breaking length, tear and burst index. With increasing filler level breaking length, tear and burst index decrease. Filler containing pulp shows a decrease in beating time for the same beating level. 20 minutes for the Valley Beater and 15000 revolutions for the PFI mill show highest change in pulp fiber beating level sufficient for paper making operation. Valley Beater and PFI Mill laboratory equipment operate different and an exact comparison of the beating curves is not possible. Based on the amount of pulp fiber needed for experiments the Valley Beater for large amounts and the PFI mill for smaller amounts should be selected. The SEM pictographs of the Valley Beater and PFI Mill beating trials from 0 stage to the high beating stage at 80 minutes for the Valley beater and 60000 revolutions for the PFI Mill show similar results. No damage to the fibers is noticeable at the unbeaten level. With increasing beating level. At a magnification of 430 times the fiber structure shows an increasing dense fiber structure with less visible pores. Magnification of 2500 times reveals increasing damage to the fiber wall and fiber surface.

Cellulosic Fiber: Mechanical Fibrillation-Morphology-Rheology Relationships

This study aims to investigate the relationship between mechanical fibrillation, morphological properties, and rheological behavior of cellulosic fiber. Three types of cellulosic fibers were obtained by adjusting mechanical fibrillation, namely squashed cellulose, incompletely nanofibrillated cellulose, and completely nanofibrillated cellulose, respectively. The squashed cellulose with large size and small aspect ratio had low entanglement capacity, thus forming a weak fiber network. The corresponding suspension exhibited low viscosity, weak elastic behavior, small yield stress, and low dynamic stability. An obviously increasing aspect ratio and entanglement capacity were observed with increasing mechanical fibrillation, resulting in entangled fiber network structure. Hence, the cellulosic fiber suspension obtained by more mechanical fibrillation exhibited higher viscosity, stronger gel-like behavior, and bigger yield stress. Moreover, the extremely entangled fiber network structure has better anti-deformation capacity and recovery capacity. We revealed the fundamental insights into the relationship between morphologies and rheological properties of cellulosic fiber, paving the way for designing cellulose-based materials.