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The effect of microfibrillated cellulose on the wet-web strength of paper, TAPPI Journal January 2021
ABSTRACT: The wet-web strength of paper immediately after the press section of a paper machine is a critical factor in determining machine runnability. However, it is difficult to determine at commercial scale, because the web has to be broken and production interrupted in order to obtain a sample for measurement. The use of microfibrillated cellulose (MFC) is believed to increase wet-web strength, as it has allowed filler level increases of 10% or more on many commercial paper machines. In this paper, we describe a laboratory method for estimating the effect of MFC on wet sheet strength after press-ing, as well as actual measurements of wet-web strength from a pilot paper machine trial. These experiments have demonstrated the positive effect of MFC. At solids contents in the range typically observed after pressing, sheets with MFC at fixed filler content are significantly stronger, but also wetter, than those without it. When the use of MFC is combined with a typical increase in filler content, the wet web remains slightly stronger, but also becomes drier than the reference condition. These results are compatible with the theory put forward by van de Ven that wet-web strength is mainly a result of friction between entangled fibers, and they also suggest that the presence of MFC increases this friction.
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Advanced real-time digital microscopy of foaming processes, TAPPI Journal January 2023
ABSTRACT: The properties of aqueous foams play a major role in foam forming and foam coating. Inline real-time foam measurements provide highly desired opportunities for optimization and control of foaming processes. This paper presents inline digital microscopy measurements of aqueous foams in foaming processes. It presents methods for providing detailed information on foam quality parameters, such as foam density and foam homogeneity in real time from the process. In addition, this study evaluates the performance of transillumination and front-light illumination in imaging of foams. The tests show very good results for the transillumination approach. Limitations of the image-based optical technique are discussed, and the precision of bubble size distribution measurement is assessed with a certificated reference substance. The measured foam densities are compared against the reference foam densities in the range 100•300 g/L, providing a linear correlation with R2 value of 0.99. In the case of heterogenous foams with a wide bubble size distribution, the bubble size-dependent dimensionless depth of field must be taken into account to obtain accurate estimates of foam density. Bubble-scale foam homogeneity is described by the standard deviation of bubble size distribution in foam.
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Pareto-based design of experiments for identifying and comparing optimum sealing parameters of heat sealing applications in packaging machines, TAPPI Journal June 2023
ABSTRACT: Sealing is one of the most important process steps in industrial packaging, because the sealed seam is the most sensitive section of a package in terms of quality. For this reason, a major focus in flexible packaging is the sealing process, and among this, heat sealing is the most frequently used technology. In detail, applications of heat sealing processes are confronted with four conflicting objectives: increasing seam quality, reducing dwell time, reducing sealing temperature, and increasing process robustness towards varying conditions. Typical problems, such as identification of the optimum process parameters or selection of the most appropriate packaging film, are subject to these conflicting objectives.This paper presents a recently published design of experiments for characterizing and comparing heat sealing properties of packaging films based on a multi-objective optimization algorithm. The approach provides easy-to-read charts showing all optimum sealing parameters with regard to the four essential objectives of heat sealing: seam quality, dwell time, sealing temperature, and process robustness. Three case studies show exemplary applications of the new approach: 1) analyzing transport damages of beverage powder packages; 2) identifying and comparing optimum sealing parameter of a standard, mono-material, and fiber based packaging film regarding tightness and visual properties of the produced sachets; and 3) analyzing the effect of additional aluminum layers on sealing characteristics regarding hot-tack.The new design of experiments may provide the basis of a standard test method for the identification of optimal sealing parameters in the heat sealing processes.
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Mineral/microfibrillated cellulose composite materials: High performance products, applications, and product forms, TAPPI JOURNAL September 2018
Mineral/microfibrillated cellulose composite materials: High performance products, applications, and product forms, TAPPI JOURNAL September 2018
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Enhancement of processability, surface, and mechanical properties of paper based on rice straw pulp using biopolymers for packaging applications, TAPPI Journal July 2019
ABSTRACT: wo biopolymers, chitosan and oxidized starch, were used as wet-end additives to improve the strength properties of the paper because of their biodegradable and non-hazardous qualities. The present study reports the improvement in surface and strength properties of packaging-grade paper made with rice straw pulp using biopolymers, chitosan, oxidized starch, and surface sizing added at the wet end of the paper machine.Use of chitosan at all doses from 0.5 to 10 kg/ton enhanced important surface and strength properties of paper. The breaking length, tear index, burst index, ring crush strength, stretch, tensile energy absorption index, and Taber stiff-ness of the paper with 10 kg/ton of chitosan as a wet-end additive showed 22%, 14%, 20%, 59%, 16%, 44%, and 48% improvement, respectively, in comparison to control, (i.e, without its addition). The Cobb60 was also reduced by 45%, showing better resistance to water in comparison to rice straw paper alone. The effects of chitosan added at the wet end on the paper surface were investigated using Fourier transform infrared spectroscopy (FTIR). The use of 10 kg/ton of chitosan at the wet end reduced the color and total suspended solids in the back water of the papermak-ing system by 55% and 51%, respectively. Further enhancement in the surface and strength properties of paper was observed following surface sizing with oxidized starch.
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Creating adaptive predictions for packaging-critical quality parameters using advanced analytics and machine learning, TAPPI Journal November 2019
ABSTRACT: Packaging manufacturers are challenged to achieve consistent strength targets and maximize pro-duction while reducing costs through smarter fiber utilization, chemical optimization, energy reduction, and more. With innovative instrumentation readily accessible, mills are collecting vast amounts of data that provide them with ever increasing visibility into their processes. Turning this visibility into actionable insight is key to successfully exceeding customer expectations and reducing costs. Predictive analytics supported by machine learning can provide real-time quality measures that remain robust and accurate in the face of changing machine conditions. These adaptive quality “soft sensors” allow for more informed, on-the-fly process changes; fast change detection; and process control optimization without requiring periodic model tuning.The use of predictive modeling in the paper industry has increased in recent years; however, little attention has been given to packaging finished quality. The use of machine learning to maintain prediction relevancy under ever-changing machine conditions is novel. In this paper, we demonstrate the process of establishing real-time, adaptive quality predictions in an industry focused on reel-to-reel quality control, and we discuss the value created through the availability and use of real-time critical quality.
Journal articles
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Kraft recovery boiler operation with splash plate and/or beer can nozzles — a case study, TAPPI Journal Octobr 2021
ABSTRACT: In this work, we study a boiler experiencing upper furnace plugging and availability issues. To improve the situation and increase boiler availability, the liquor spray system was tuned/modified by testing different combinations of splash plate and beer can nozzles. While beer cans are typically used in smaller furnaces, in this work, we considered a furnace with a large floor area for the study. The tested cases included: 1) all splash plate nozzles (original operation), 2) all beer can nozzles, and 3) splash plate nozzles on front and back wall and beer cans nozzles on side walls. We found that operating according to Case 3 resulted in improved overall boiler operation as compared to the original condition of using splash plates only. Additionally, we carried out computational fluid dynamics (CFD) modeling of the three liquor spray cases to better understand the furnace behavior in detail for the tested cases. Model predictions show details of furnace combus-tion characteristics such as temperature, turbulence, gas flow pattern, carryover, and char bed behavior. Simulation using only the beer can nozzles resulted in a clear reduction of carryover. However, at the same time, the predicted lower furnace temperatures close to the char bed were in some locations very low, indicating unstable bed burning. Compared to the first two cases, the model predictions using a mixed setup of splash plate and beer can nozzles showed lower carryover, but without the excessive lowering of gas temperatures close to the char bed.
Journal articles
Pre-damping effects on water absorption and drying dynamics in flexographic printing, TAPPI Journal November 2025
ABSTRACT: Optimizing flexographic printability can involve the ink and the substrate, as well as the printing process. It has been widely reported in the literature that controlling topography of the substrate and its porosity are vital for good flexographic printability, especially when using water-based inks. This study focuses on how pre-damping a surface impacts liquid absorption and improves wet trapping (ink on ink with no intermediate drying) in flexographic printing. A Prüfbau universal print tester was adapted to analyze flexographic wet-on-wet ink printing and trapping using yellow and magenta inks for contrast. Slow drying of the first ink layer (yellow) leads to mottle when the second layer (magenta) is applied. The study explores the “wet sponge” hypothesis: a pre-damped surface should absorb liquid faster. The Lucas- Washburn equation describes long-term absorption, but it does not capture short-term uptake, which instead follows a linear dependence on time.
Journal articles
ABSTRACT: Laboratory experiments with bleached kraft furnish were carried out to quantify the effects of major differences in electrical conductivity of papermaking process water (due to the addition of sodium sulfate) on the performance of various paperm
ABSTRACT: Laboratory experiments with bleached kraft furnish were carried out to quantify the effects of major differences in electrical conductivity of papermaking process water (due to the addition of sodium sulfate) on the performance of various papermaking additives. Batches of refined pulp were prepared with conductivity levels of 168 (tap water), 1000, and 10,000 ìS/cm. The absolute values of the calculated zeta potential, in various cases, were shown to decrease with increasing logarithm of electrical conductivity. The performance of retention aid systems, including cationic polyacrylamide (cPAM), were not adversely affected by increased salinity, even up to an electrical conductivity level of 10,000 ìS/cm. In fact, treatment involving sequential addition of cPAM and colloidal silica showed superior retention of mineral filler at the highest conductivity level. Likewise, combinations of papermaking additives that promote the dewatering of paper continued to perform well in furnish prepared with increasing salinity. The ability of various chemical systems to induce flocculation among papermaking fibers decreased moderately at the highest level of salinity considered.
Journal articles
Magazine articles
Predicting strength characteristics of paper in real time using process parameters, TAPPI Journal March 2022
ABSTRACT: Online paper strength testing methods are currently unavailable, and papermakers have to wait for manufacture of a complete reel to assess quality. The current methodology is to test a very small sample of data (less than 0.005%) of the reel to confirm that the paper meets the specifications. This paper attempts to predict paper properties on a running paper machine so that papermakers can see the test values predicted in real time while changing various process parameters. This study was conducted at a recycled containerboard mill in Chicago using the multivariate analysis method. The program provided by Braincube was used to identify all parameters that affect strength characteristics. Nearly 1600 parameters were analyzed using a regression model to identify the major parameters that can help to predict sheet strength characteristics. The coefficients from the regression model were used with real-time data to predict sheet strength characteristics. Comparing the prediction with test results showed good correlation (95% in some cases). The process parameters identified related well to the papermaking process, thereby validating the model. If this method is used, it may be possible to predict various elastic moduli (E11, E12, E22, etc.) in the future as the next step, rather than the traditional single number “strength” tests used in the containerboard industry, such as ring crush test (RCT), corrugating medium test (CMT), and short-span compression strength test.