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Journal articles
Theoretical Drying Study of Single-Tier Versus Conventional
Theoretical Drying Study of Single-Tier Versus Conventional Two-Tiered Dryer Configurations, 1992 Engineering Conference Proceedings
Journal articles
Editor's Notes: Ready for a Test Drive, TAPPI JOURNAL, Novem
Editor's Notes: Ready for a Test Drive, TAPPI JOURNAL, November, 2006
Journal articles
Paper strength factors in systems with nanofibrillated cellulose, cationic starch, colloidal silica, cationic acrylamide copolymer, and hydrodynamic shear, TAPPI Journal May 2025
ABSTRACT: Laboratory paper sheets were formed by first pretreating nanofibrillated cellulose (NFC) with cationic starch at the 5% level by mass. The treated NFC was then added to stock prepared from 100% recycled copy paper. The combined furnish was next optionally treated with a cationic retention aid (cPAM, 0.1%) and then colloidal silica (0.1% or 0.2%). Vacuum dewatering, fine-particle retention, and several paper properties were studied as a function of the colloidal silica level (zero, 1%, and 2%) and at different levels of shear stress applied just before forming the sheets. Dewatering and strength results were generally more favorable when using a medium charge cationic starch (~ 0.03 degree of substitution, DS) to pretreat the NFC rather than a high charge density cationic starch (~ 0.2 DS). In each case, the dewatering was further enhanced by subsequent treatments by cPAM (0.1% on whole furnish solids) and then even more with the final addition of colloidal silica (0.1% and 0.2% levels compared). However, the colloidal silica additions progressively hurt the tensile strength of the paper, especially in the case of the high charge cationic starch and at the higher level of colloidal silica. Though the dewatering performance was favorable, in such cases, the paper strength was not improved compared to paper made without any NFC. The fact that the systems involving cPAM treatment, and especially those involving both cPAM and colloidal silica, tended to reduce the resulting paper’s tensile strength supports a mechanism in which the additives result in the clustering of the NFC, possibly in multiparticle bunches. Evidence suggests that such bunches of clustered NFC particles, which are difficult to redisperse even at levels of hydrodynamic shear present in high-speed paper machine systems, are resistant to full integration into the sheet structure as the paper is being formed.
Journal articles
Colloidal silica and its effects during formation of paper sheets in the presence of nanofibrillated cellulose, cationic starch, and cationic acrylamide copolymer, TAPPI Journal May 2025
ABSTRACT: This work considered effects of colloidal silica addition during laboratory preparation of paper sheets containing nanofibrillated cellulose (NFC) that had been pretreated with cationic starch. The emphasis was on process performance issues, including dewatering rates, fine particle retention, and the extent of fiber flocculation. In addition, micrographs were obtained to show what was happening to the NFC upon treatments with cationic starch and subsequent application of hydrodynamic shear. Contrasting results were obtained, depending on the charge density of the cationic starch. Pretreatment of the NFC with a high charge density cationic starch (degree of substitution 0.2) resulted in strong interactions with the colloidal silica, enhancing the dewatering rate and contributing to fine-particle retention. The medium charge cationic starch pretreatment led to effects suggesting a bridging mechanism of action, and subsequent colloidal silica had no significant effect on dewatering. Treatment of that system with a high level of colloidal silica (0.2%) resulted in lower retention. In general, the final colloidal silica treatments tended to decrease the level of flocculation in the suspensions, giving more uniform handsheets. Mechanisms, some of them related to the clustering and dispersion of cationic starch-treated NFC, were proposed to account for the observed effects.
Journal articles
Magazine articles
Dynamic compression characteristics of fiber-reinforced shoe press belts, TAPPI Journal April 2025
ABSTRACT: Shoe press belts contribute significantly to the overall dewatering performance in the press section of a paper machine. Within the shoe press nip, the press belt faces a dynamic and multidimensional load that mainly leads to a compression of the structure. As this will cause a loss in void volume, knowledge of the dynamic compression characteristics of shoe press belts is crucial for optimized dewatering. A novel method was developed to examine the dynamic compression characteristics of grooved polyurethane press belts. Therefore, an experimental setup allowing realistic boundary conditions to test specimens was placed in a servo-hydraulic testing machine. Press belt specimens with different matrix material formulations and groove patterns were tested under varying load rates equivalent to different paper machine operational speeds. The results showed an evident sensitivity of the dynamic compression stiffness to the operational speed of the paper machine. This behavior was seen to be more sensitive to changes in the matrix material formulation than to adaptions of the groove pattern. As a result, the compression of the press belt within a shoe press nip is not only influenced by the peak pressure within the shoe press nip but also depends on the operational speed of the paper machine.
Journal articles
Research on an energy model for X-ray measurement of paper ash content using COMSOL, TAPPI Journal May 2025
ABSTRACT: Ash content is one of the critical quality parameters in papermaking production. Traditional 55Fe radioactive sources used for online ash content measurement have a short lifespan and high costs, while offline methods such as the combustion method or chemical analysis are time-consuming. Using an X-ray tube as the radiation source, continuous X-ray measurement offers advantages such as being rapid, non-destructive, and cost-effective. In this study, COMSOL software was employed to simulate the measurement process and establish an energy attenuation model for X-ray measurement of paper ash content. The model simulates the energy attenuation of X-rays before and after transmission through four materials: calcium carbonate (CaCO3), titanium dioxide (TiO2), wood-based plant fibers, and paper samples filled with CaCO3. The absorption coefficients of paper samples with varying ash content were investigated using the model and compared with experimental results obtained from continuous X-ray measurements. The results indicate that the proposed energy simulation model can reduce the measurement error of paper ash content by 1%, significantly enhancing the reliability and accuracy of ash content measurement.
Journal articles
Water-based adhesive penetration into paperboard and coated paperboard, TAPPI Journal January 2025
The setting of water-based adhesives in contact with paperboard is important in the production of boxes and other packaging, but the topic has received little attention in the literature. The penetration of the adhesive into the paper surface is important to get good bond strength through mechanical interlocking. The influence of the process conditions and the paper properties on this penetration is lacking. A water-based adhesive was applied to an uncoated and coated paperboard. The coating layer had two latex levels. Samples were characterized in terms of air permeability, void fraction, average pore size, and coat weight. The adhesive was applied to the samples in a mechanical press, squeezing a drop between two samples. The penetration of the adhesive was characterized with a silicone oil absorption method that measured the decrease in pore volume after the adhesive had been applied to approximate the pore volume taken up by the adhesive. The bond strength was measured with a peeling test. The penetration depth into uncoated paper did not depend on the application method parameters such as pressing time, pressure, or initial solids of the adhesive. The penetration depth ranged from 35•40 mm. The penetration into 10 pph latex content coated paper was similar to the uncoated samples, but reduced penetration was observed into the 40 pph latex content coatings. The results were compared to the limiting amount of adhesive that was obtained from the weight gain of the samples and to a simple model that is based on flow in porous media. Peel tests revealed that good penetration was needed, as well as a strong coating layer to obtain high peel forces.
Journal articles
Comparison of the application of polysaccharide-based barrier coatings on paper using film press and spray coating, TAPPI Journal January 2025
The growing demand for sustainable packaging has spurred research into biopolymer-based solutions and their application to paper substrates. This study compares the application of low solids, high viscous aqueous solutions of alginate and chitosan on two different paper substrates using a laboratory film press coater and a purpose-built spray coating unit, with a focus on barrier performance and practical industry considerations. Key parameters investigated are air flow rate, water vapor transmission rate, and grease resistance. Results showed that due to the low solids content of the applied biopolymer solutions, film press coating required a double-layer application for coat weights exceeding 4 g/m², making it less viable for industrial application. In contrast, spray coating allowed for higher application weights in a single step. The barrier properties of spray coated samples, compared to film press coatings, varied with the paper substrate: spray coating performed better on one substrate and worse on the other. Contact angle measurement of the substrates suggested that spray coating is more suitable for a more hydrophilic substrate because of improved surface wetting. The study also identified issues with drying conditions and pinholes affecting the quality of spray coated samples, indicating a need for further research to optimize these parameters.
Journal articles
Editorial: Fundamental understanding enables new coating opportunities, TAPPI Journal January 2025
TAPPI's Coating, Printing, and Surface Enhancement (CPSE) Division pursues open exchange of technical information related to materials, equipment, and processes for the manufacture, quality control, and use of coated papers, paperboard, and other substrates. Much of this technical information is presented at sponsored conferences, including TAPPICon and the Advanced Coating Symposium. Based on feedback from these events, TAPPI Journal peer reviews the research from these events that adds significant value to the scientific community. In last year's November issue, we presented five peer-reviewed manuscripts based on presentations given at TAPPICon 2024.
Journal articles
Optimization of optical coverage of board surfaces with assessment of light scattering and absorption using mineral as a coating component, TAPPI Journal June 2026
ABSTRACT: One of the primary functions of mineral inclusion into paper or paperboard is to improve the optical performance of the substrate. A coating may be applied to a sheet in order to cover a dark base, to improve the sheet opacity, to give the correct smoothness and gloss, or to give a suitable surface on which to print. The brightness of a pigment has long been used as a guide for pigment choice in paper and board. However, the measured paper brightness is a function of color and light absorption (K) of the coating and base and the light scattering (S) within the sheet resulting from interfaces with different refractive index. The optical performance can be quantified by measuring the S&K coefficients as described by the Kubelka-Munk model/theory in a filled or coated paper sheet. In coating, this is often assessed as a function of coat weight, and the corresponding physical sheet properties are assessed at the same time; for example, the correct gloss, smoothness, point-to-point uniformity, and printability. The optical performance in the sheet is often not directly related to the pigment brightness, but is largely a function of the particle packing within the sheet and coating layer. In the first and second main sections of this work, respectively, we show how S&K calculations from the Kubelka- Munk equations can be used in coated sheets to determine the optical performance and how this can be used as a predictive tool for the final sheet performance. This is presented for base sheets with different starting brightness. The third section of this work focuses on how mineral combinations in coatings can be used to improve the light scattering and consequently the optical performance of the board. We include theoretical considerations and then finally share a case study for improvement on the optical properties of recycled board.