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Journal articles
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Rheological characteristics of platy kaolin, TAPPI JOURNAL September 2019
ABSTRACT: Platy kaolin can provide significant value in the coating of paper and paperboard. It can be used in multiple applications and can provide benefits such as titanium dioxide (TiO2) extension, smoothness improvement, improved print gloss or ink set rates, calendering intensity reduction, and improved barrier properties. It is not a pigment that can be simply substituted for traditional hydrous kaolin without some adjustment to the coating formulation. These adjustments can be as simple as reducing solids, but may require binder changes as well. The coater setup may need to be adjusted because of the unique rheological behaviors these pigments exhibit.The unique rheological characteristics of platy kaolin are explored here. Measurements of the water retention of platy kaolin containing coatings confirm that water retention is not reduced in comparison to more blocky kaolin pigments, despite the lower coating solids at which they need to be run. This means that the rheological characteristics are the most important in understanding the runnability. An extensive analysis reveals some unique behaviors that need to be understood when utilizing these materials. Viscoelastic measurements indicate that, for this binder system, Tan d is mainly a function of solids. This may explain how weeping is initiated on a blade coater. The degree of shear thinning behaviors is investigated using the Ostwald de-Waele power law. The immobilization point was determined using the Dougherty-Krieger equation and related to the work of Weeks at the University of Maine on blade coater runnability. An indirect measure of particle shape and size synergy is also demonstrated using the Dougherty-Krieger equation parameters.
Journal articles
Magazine articles
Application of fuzzy TOPSIS in the Analyze phase of the DMAIC cycle to aid decision-making, TAPPI Journal April 2020
ABSTRACT: This paper reports the use of multicriteria analysis in the Analyze phase of the DMAIC (Define-Measure-Analyze-Improve-Control) cycle for continuous improvement. The research was carried out in a tissue paper factory located in southern Brazil. A sample of 64 parts of 16 different reels of recycled paper was used. A problem regarding paper quality variability was detected, presenting a scrap index ranging between 9% and 23%, compromising machine productivity and product sales. This motivated the implementation of a structured project supported by the application of the DMAIC cycle. The project team (machine operators, maintenance staff, supervisor, and data analyst) defined the evaluation criteria and determined the control intervals and their equivalence with linguistic variables to support the necessary evaluations for the application of fuzzy TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). The criteria were C1-Longitudinal Strength (Kgf), C2-Longitudinal Elongation (mm), C3-Cross-strength (kgf), C4-Cross-elongation (mm), C5-Weight (g/m²), and C6-Humidity (%). The results showed that samples with the same ranking had the lowest scrap indexes in the subsequent process. Also, the criterion C5 had a more significant impact on the quality of the product than the other criteria, which was determined from the DMAIC sequence. Improvements related to C5 should be prioritized. The fuzzy TOPSIS method presented is a flexible tool, adapting itself to the solution of the problem and contributing to the decision-making process.
Journal articles
Magazine articles
Guest Editorial: Still working (overtime): Life-saving nonwovens and continued innovation, TAPPI Journal August 2021
ABSTRACT: Recently, the United States federal government has recommended the need for a booster shot to combat COVID-19, highlighting the highly contagious nature of its Delta variant. This variant is surging in countries as far apart as Thailand, Brazil, and the United States. While the availability of the vaccine is not an issue in the United States, African, Latin American, and South Asian countries are in dire need of the vaccine. This scenario necessitates the need for continued safety measures. Among the recommended safety measures, use of face masks has been proven to be effective. Recent analysis showed that two-thirds of the 32 states in the United States with face mask mandates found them helpful for lowering infection rates.
Journal articles
Magazine articles
Key material properties in crease cracking of kraft paper, TAPPI Journal February 2021
ABSTRACT: Crease cracking of paperboard is important to control for the appearance and structural integrity of packages. Crease cracking is affected by creasing operation variables, as well as the physical properties of the paperboard. However, the effects of the physical properties are not clearly known. The objectives of this work were to identify the key material properties that affect crease cracking and to clarify the effects of fiber composition and starch. Laboratory sheets were produced from bleached and refined softwood and hardwood commercial pulp at grammage and thicknesses that match a typical paperboard. To mimic papermaking operations, surface starch was applied via a bench-top size press. The sheets were creased in the lab over a range of penetration depths, and reverse-side cracking was measured. The results showed that less reverse-side cracking was correlated with higher tensile post-peak energy, a lower bending stress, and a lower z-direction (ZD) stiffness. The tensile post-peak energy is a measure of the resistance to crack growth via fiber-bridging. The bending force and the ZD stiffness influence the forces that create cracks. It was observed that decreasing the ratio of hard-wood-to-softwood content and reducing the amount of starch would both decrease crease cracking.
Journal articles
Magazine articles
Application of foamed additives to the surface of wet handsheets, TAPPI Journal January 2021
ABSTRACT: We explored the application of foamed wet-end additives onto wet handsheets to qualify our method of application and to demonstrate the method’s usefulness for prescreening additives and foaming agents for packaging applications.We modified a laboratory drawdown coating machine to allow coating of wet handsheets with foamed additives. Initial sheet solids were adjusted to a target of 8%•25% by vacuum. Foam layer thickness was set mechanically. After application, the foamed additives were drawn into the sheet with vacuum. The additive dosage was adjusted by altering its concentration within the foaming formulation. We evaluated more than 100 foaming agents and 10 strength additives, comparing wet-end and foam-assisted addition with no addition on recycled linerboard and virgin linerboard furnish. Foam-assisted addition typically displayed a much steeper dose-response curve and much higher maximum strength levels than wet-end addition. Our results suggest potential target applications for this technology, such as lightweighting, and improved strength performance in mills with relatively closed water systems, where strength aids added into the wet end are adversely influenced by accumulation of inorganic ions and organic species.
Journal articles
Magazine articles
The effect of contact time between CPAM and colloidal silica on the flocculation behavior in the approach flow, TAPPI Journal January 2021
ABSTRACT: Multicomponent wet-end systems have become increasingly common in papermaking, with the objective of improving the retention-formation-dewatering relationship. It is quite common to use at least a cationic polymer, often in combination with an anionic microparticle. In some cases, a fixative is also used. However, there is still debate on the optimal implementation of these systems. In particular, optimizing the contact time of the cationic polymer prior to addition of the anionic microparticle is still poorly understood. In this work, we investigate the effect of the contact time of a cationic polyacrylamide (CPAM) prior to addition of colloidal silica on the flocculation response in a flowing fiber suspension. The effect of using a fixative is also investigated. Focused beam reflectance measurements (FBRM) are combined with zeta-potential measurements for optimizing the addition levels of a two- and three-component system, as well as for elucidating the effect of contact time on CPAM performance. Trials are then performed on a pilot scale flow loop, where the time between addition of these two components is varied and the resulting flocculation response is characterized using high-speed filming and image analysis techniques. It is shown that the efficacy of CPAM can be improved through use of a fixative and that a longer CPAM contact time may be beneficial in terms of immediate flocculation; however, hydrodynamic shear tends to dominate the flocculation response regardless of contact time due to floc rupture.
Journal articles
Magazine articles
Setting priorities in CNF particle size measurement: What is needed vs. what is feasible, TAPPI Journal February 2023
ABSTRACT: Measuring the size of cellulose nanomaterials can be challenging, especially in the case of branched and entangled cellulose nanofibrils (CNFs). The International Organization for Standardization, Technical Committee 6, Task Group 1—Cellulosic Nanomaterials, is exploring opportunities to develop standard methods for the measurement of CNF particle size and particle size distribution. This paper presents a summary of the available measuring techniques, responses from a survey on the measurement needs of CNF companies and researchers, and outcomes from an international workshop on cellulose nanofibril measurement and standardization. Standardization needs differed among groups, with Japanese companies mostly requiring measurements for product specification and production control, and other companies mostly needing measurements for safety/regulatory purposes and for grade definitions in patents. Among all the companies, average length and width with percen-tiles (D(10), D(50), D(90)) were the most desired measurands. Workshop participants concurred that defining the location(s) on the CNF at which to measure the width and the length is an urgent and complex question. They also agreed that methods are needed for rapid particle size measurement at the nanoscale. Our recommendation within ISO is to start work to revise the definition of CNFs and develop sample preparation and measurement guidelines. It was also recommended that further research be done to reproducibly prepare hierarchical branched CNF structures and characterize them, develop automated image analysis for hierarchical branched CNF structures, and develop a classification system encompassing measurements at multiple size ranges from micro- to nanoscale to fully characterize and distinguish CNF samples.
Journal articles
Magazine articles
Effect of fly ash-based calcium silicate on physical properties of cardboard paper, TAPPI Journal July 2023
ABSTRACT: This work reported the possibility of using fly ash-based calcium silicate (FACS) as filler for papermaking and waste fiber to synthesize cardboard paper. The adverse effects of FACS filler on paper strength were improved by using cationic starch modification, surface size, and interlayer-filled technology. Physical property tests indicated that the increase of filler content leads to a decrease in paper strength and an increase in bulk, but at the same content, the strength properties of paper modified by cationic starch were significantly improved, and the absorption resistance was lower. The paper had better absorption resistance than the original FACS paper after surface size. In addition, the absorption resistance and strength of the interlayer filling paper were better than the original FACS-filled paper, and the absorption resistance was the best. The results support the potential use of FACS as a low-cost filler for cardboard paper production.
Journal articles
Magazine articles
On the diagnosis of a fouling condition in a kraft recovery boiler: combining process knowledge and data-based insights, TAPPI Journal March 2023
ABSTRACT: Fouling is still a major challenge for the operation of kraft recovery boilers. This problem is caused by accumulation of ash deposits on the surfaces of heat exchangers in the upper part of the boiler over time. The first consequence is the reduction of steam production due to loss of heat transfer and, finally, the shutdown of the boiler due to clogging. The present work investigated the operational condition of a modern kraft boiler under a critical fouling condition. This boiler had even faced a manual cleaning due to a clogging event. This analysis combined process knowledge, plant team experience, and a data-driven approach, given the complexity of the process. In this sense, historical data covering this critical period of operation were collected. After a cleaning procedure, they were used to obtain a predictive neural network model for the flue gas pressure drop in the boiler bank, which is an indirect measure of ash deposit accumulation. Once validated, it was used for sensitivity analysis, with the aim of quantifying the effects of the model inputs. Five variables out of eighteen accounted for nearly 60% of the total effect on pressure drop. Namely, primary air temperature (21.6% of the total effect) and flow rate (11.1%), black liquor flow rate (9.9%) and temperature (8.4%), and white liquor sulfidity (8.6%). The analysis of these results mainly suggested an excess of carryover, which composes the ash deposits. Recommended actions to mitigate the fouling condition involved adjustments to the primary air system before the more drastic solution of reducing the boiler load.
Conference papers
Efficient tissue process for cost reduction and material sav
Efficient tissue process for cost reduction and material savings: simulation-enhanced process development and performance optimization, Tissue2017