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Quantification of block testing for coated paper substrates, TAPPI Journal November 2024
ABSTRACT: Block resistance is a critical property for coated paper and board substrate that will be rolled, stacked, or otherwise contact itself after coating. Small differences in the coated substrate’s blocking can determine whether the substrate can be successfully used for its designated purpose. However, this crucial property is typically evaluated using a qualitative scale that is based on subjective operator ratings and impacted by factors that include: (1) sound of coated substrate during separation, and (2) force with which substrates are separated. This paper tests the hypothesis that quantifying the block test by measuring the force required to peel samples apart improves the test by: (1) providing more standardized testing conditions by controlling peel force and rate; (2) more clearly differentiating samples that experience minimal to some blocking; and (3) maintaining customizability to evaluate customer-specific test conditions. The method developed in this study uses a standard block tester and block testing conditions, but it peels the coated paper samples using a hot tack/heat seal instrument with force measurement capabilities. This paper demonstrates, using the instrument’s heat seal capabilities, that it can measure peel forces that represent the full range of observable block scores. The efficacy of this method was evaluated by having a group of trained operators engage in a randomized, blind experiment where they assessed block resistance on a set of coated paper samples using a modified qualitative block scale and compared their results to force measurements collected using the proposed method. The sample set included two coatings that have successfully run in commercial trials with minimal blocking, and one coating that experienced significant blocking in commercial trials despite only exhibiting some blocking at standard block test conditions in laboratory testing. The quantitative test method presented in this paper clearly differentiated these samples, whereas the qualitative assessment could not predict which samples had suitable block resistance for commercial use. As any tensile tester capable of measuring with 0.1 N resolution can be used for the Quantitative Block Test, the proposed method can be widely adopted. Furthermore, this method can be used for any block condition.
Journal articles
A targeted approach to produce energy-efficient packaging materials from high-yield pulp, TAPPI Journal August 2025
ABSTRACT: Unlike fossil-based plastics, wood-based packaging materials can be produced in an ecofriendly manner using wood chip residuals from sawmills and pulpwood. To produce high-yield pulp like chemithermomechanical pulps (CTMPs) for paperboard and liquid packaging, it is crucial to reduce the electric energy consumption during fiber separation. The ultimate objective is to revolutionize paperboard production by achieving a middle-layer CTMP process that consumes less than 200 kilowatt-hours per metric ton (kWh/t), significantly improving from the current 500•600 kWh/t energy demand. Optimizing the CTMP impregnation process of sodium sulfite (Na2SO3) in wood chips is crucial for achieving uniform softening, ideally at the fiber level. The properties of the fibers are significantly affected by the content of lignin sulfonates within the walls of the fiber and the middle lamellae. In this study, we employed in-house developed X-ray fluorescence (XRF) techniques, validated by beamline measurements, to map the distribution of sulfonated lignin within fibers. It also seemed possible to enhance the surface area of lignin-rich pulp fibers while losing minimal bulk by refining them with well-optimized low consistency (LC) refining. We aimed to achieve a highly efficient separation of coniferous wood fibers by co-optimizing the sulfonation and the temperature in the preheater and chip refiner. Additionally, we explored how lignin’s softening behavior and potential crosslinking influence subsequent unit operations, including pressing, peroxide bleaching, and drying, following the defibration process. In defibration during chip refining, the maximum softening of wood fibers is preferred to maximize fiber preservation and minimize energy consumption. However, optimizing the stiffness of finished pulp fibers is preferable to reduce bulk loss during paperboard production. It can strive to optimize processes to develop stronger, lighter, and more sustainable composite packaging materials. Reducing environmental impact and electric energy can help create a more sustainable future.
Journal articles
Conversion of paper-grade pulp from rice straw into dissolving pulp, TAPPI Journal June 2025
ABSTRACT: About 1,165 million metric tons of rice straw is generated every year worldwide, which can be a good source for the circular bioeconomy. In this research paper, the paper-grade pulp from rice straw was converted to dissolving-grade pulp by fractionation in a biorefinery initiative. Rice straw was cooked at an optimum condition of 8% potassium hydroxide (KOH) charge for 120 min at 150°C and produced a pulp yield of 47.2% with a kappa number of 18.5. Subsequently, D0(EP)D1 bleaching was carried out for the produced pulp, and the brightness of the pulp reached to 82.4%. From the black liquor, 16.5% of the lignin and 11.9% of the hemicellulose were isolated for producing biobased products and chemicals, and then the spent liquor was used for soil amendment. The bleached pulp was fractionated in a Bauer McNett fiber classifier. The pulp fibers retained on 16-, 30-, and 50-mesh screens were used as a longer fiber fraction pulp, and pulp fibers retained on 100- and 200-mesh screens were used as a shorter fiber pulp. The longer and shorter fiber fraction pulps were analyzed for cellulose, R10, pentosan, and viscosity. The long fiber fraction pulps were characterized by higher cellulose (88.2% vs. 83.1%) and lower pentosan (11.3% vs. 13.0%) content than the shorter fiber fraction pulps. The longer fiber fraction was further treated with cold KOH to remove residual hemicellulose. The KOH extraction reduced pentosan content in pulp to 6.3% and increased á-cellulose content to 91.3%. The short fiber fraction was converted to monomeric sugars using cellulase enzymes with varying reaction time, temperature, and consistency. The efficiency of cellulase activity was assessed through glucose yield and residual dry weight. A temperature of 45°C, 5.0 pH, 5% consistency, and 6 filter paper units/gram (FPU/g) o.d. pulp resulted in maximum sugar conversion of 85.7%.
Journal articles
Aging and degradation of oil and grease barrier papers coate
ABSTRACT: The long-term performance and stability of bio-based barrier coatings are critical for sustainable packaging. In this study, the aging and degradation of a biobased starch•wax emulsion coating were examined on two different base papers. Coated samples were stored for 8 months at 23°C and 50% relative humidity (RH) in their original reels to minimize external exposure and isolate internal aging effects. Multiple aging intervals were analyzed using advanced methods to assess both chemical composition and physical structure. The water vapor transmission rate (WVTR) of both coated papers increased during the first 15 days, but after eight months, the WVTR dropped below the initial values. Fourier transform infrared (FTIR) results supported these trends by showing a marked rise in the polarity index (PI), occurring predominantly within the first 15 days. The overall observations, including increases in the PI, carbonyl index (CI), and absolute absorbance in the hydroxyl region, confirm that both hydrolysis and oxidation occurred during aging. The gradual increase in the aliphatic C•H stretching peaks indicated that wax components moved toward the surface over time. The non-uniform surface enrichment of oleophilic wax following migration contributed to the decline in Kit rating upon aging by facilitating oil and grease wetting and penetration. At the same time, increased wax concentration at the surface helped improve the water vapor barrier performance during long-term aging. Scanning electron microscopy (SEM) imaging revealed distinct surface cracks over time on the starch-wax emulsion coated papers. The FTIR analysis supported these observations through an increase in the conformational disorder index (CDI) with aging. Physical changes were further reflected in the barrier performance, as the heptane vapor transmission rate (HVTR) increased significantly for both coated papers over the 8-month period.
Journal articles
A novel dimensionless index for optimizing the thermo-hydrau
ABSTRACT: The comprehensive performance of steam condensation in horizontal rotating channels, which involves a trade-off between heat transfer enhancement and flow resistance, lacks a unified evaluation criterion. This deficiency is particularly critical for applications such as a multi-channel cylinder dryer (MCD) in paper machines, where rotational operation enhances drying efficiency. To address this gap, this study introduces a novel dimensionless index, W/Eu, defined as the ratio of the dimensionless heat transfer coefficient (W) to the dimensionless pressure drop (Eu), thereby taking into account both heat transfer and flow resistance characteristics comprehensively. A functional relationship for this index was established with respect to channel spacing (Wr) and steam mass flux (G), followed by a theoretical optimization analysis. The analysis reveals that W/Eu decreases monotonically as Wr increases and increases monotonically as G increases, ultimately diverging as G ™¨ ™‡. Consequently, for any given operational range, the theoretical maximum performance is achieved at the boundary condition of minimum channel spacing (Wr ™¨ 0) and maximum allowable mass flux (G = Gmax). This work provides a clear theoretical directive for the design and optimization of high-efficiency rotating heat exchanger systems, offering valuable insights for enhancing the drying performance of microchannel dryers in paper machines and similar rotary thermal systems.
Journal articles
Magazine articles
Rethinking the paper cup — beginning with extrusion process optimization for compostability and recyclability, TAPPI Journal June 2021
ABSTRACT: More than 50 billion disposable paper cups used for cold and hot beverages are sold within the United States each year. Most of the cups are coated with a thin layer of plastic — low density polyethylene (LDPE) — to prevent leaking and staining. While the paper in these cups is both recyclable and compostable, the LDPE coat-ing is neither. In recycling a paper cup, the paper is separated from the plastic lining. The paper is sent to be recycled and the plastic lining is typically sent to landfill. In an industrial composting environment, the paper and lining can be composted together if the lining is made from compostable materials. Coating paper cups with a compostable performance material uniquely allows for used cups to be processed by either recycling or composting, thus creating multiple pathways for these products to flow through a circular economy.A segment of the paper converting industry frequently uses an extrusion grade of polylactic acid (PLA) for zero-waste venues and for municipalities with ordinances for local composting and food service items. The results among these early adopters reveal process inefficiencies that elevate manufacturing costs while increasing scrap and generally lowering output when using PLA for extrusion coating. NatureWorks and Sung An Machinery (SAM) North America researched the extrusion coating process utilizing the incumbent polymer (LDPE) and PLA. The trademarked Ingeo 1102 is a new, compostable, and bio-based PLA grade that is specifically designed for the extrusion coating process. The research team identified the optimum process parameters for new, dedicated PLA extrusion coating lines. The team also identified changes to existing LDPE extrusion lines that processors can make today to improve output.The key finding is that LDPE and PLA are significantly different polymers and that processing them on the same equipment without modification of systems and/or setpoints can be the root cause of inefficiencies. These polymers each have unique processing requirements with inverse responses. Fine tuning existing systems may improve over-all output for the biopolymer without capital investment, and this study showed an increase in line speed of 130% by making these adjustments. However, the researchers found that highest productivity can be achieved by specifying new systems for PLA. A line speed increase to more than 180% and a reduction in coat weight to 8.6 µm (10.6 g/m2 or 6.5 lb/3000 ft2) was achieved in this study. These results show that Ingeo 1102 could be used as a paper coating beyond cups.
Journal articles
Beyond the machine: Decoding process water microbes behind odor in papermaking, TAPPI Journal February 2026
ABSTRACT: Paper manufacturing processes create an ecosystem conducive to microbial growth, characterized by abundant water, nutrients, and optimal temperatures, fostering diverse microbial habitats. With the increased use of recycled fibers and greater water system closure, the industry now faces amplified microbiological challenges, particularly odor generation. These odor problems have raised community concerns, as shown by resident com-plaints, and have led to significant economic impacts, including costly lawsuits against major paper manufacturers. Based on earlier studies showing that microbes in papermaking systems can generate odor-causing volatile com-pounds, this study is guided by the hypothesis that recycle paper mill process water harbors odor-causing microbial communities and thus represents a primary source of malodor. To test this hypothesis, process water samples from commercial recycle paper mills were analyzed using high-throughput Illumina sequencing to characterize microbial communities in one complete analysis. The study results revealed fifteen major microbial populations, dominated mainly by the genus Pseudomonas. The identified microbes were further linked to prior literature to determine their functional roles in odor generation, including the production of haloanisoles (2-monochloroanisole, 2,4-dichloroanisole, 2,3,6-trichloroanisole, 2,4,6-tri-bromoanisole), geosmin, 2-methylisoborneol, and volatile organic sulfur compounds such as dimethyl polysulfides, hydrogen sulfide, and methylmercaptan. This study introduces a microbiological community-profiling approach that enables papermakers to assess whether process water represents a potential source of malodor. Earlier studies have not examined microbial com-munities in recycle paper mill process water specifically from the perspective of identifying malodor sources, nor have they integrated such findings with an extensive literature-based assessment. The findings of this study advance both science and practice by offering a method that can serve as an early diagnostic tool for papermakers, supporting effective future odor management and deepening understanding of microbial ecology in paper mill environments.
Water chemistry challenges in pulping and papermaking – fundamentals and practical insights: Part 1: Water chemistry fundamentals and pH, TAPPI Journal June 2022
ABSTRACT: Water is an essential component of the papermaking process. Nevertheless, papermakers often overlook its importance compared to fibers and chemical additives. A better understanding of water properties and chemical interactions associated with water at the wet end leads to a sound foundation for high-quality paper production and smooth operation. Not all fresh water and process water is the same. Fresh water varies from mill to mill, primarily due to the location and availability of water sources. Some industrial trends, such as enhancing water conservation and production yield, gradually shift process water quality over time. The current work serves as a primer on water and water chemistry fundamentals to help the papermaker prepare for the future challenges of increased contamination of process water associated with reduced fresh water usage. This paper focuses on basic water chemistry definitions and discusses the impact of pH on wet-end operation. It is clear that pH is a fundamental factor that directly affects the process and impacts other factors relevant to the papermaking process. It is crucial to understand what pH represents, how it is measured, how to select the proper pH and carefully control it, and how to closely maintain the process at target setpoints. Understanding the sensitivity of operation to pH change will lead to an appropriate focus on these issues. In addition to basic theory, we also review onsite experience and practical mill cases. It is imperative to stress that, although critical, pH is not the only chemical parameter impacting papermaking operations. Other factors, such as ionic concentration measured by conductivity, surface, soluble charge, and hardness, are critical and will be discussed in Part II of this series. As pH is a primary and independent factor that impacts various forms of charge and conductivity, the authors decided to start the current series of papers by discussing pH.
Journal articles
Magazine articles
Temperature profile measurement applications of moving webs and roll structures with intelligent roll embedded sensor technology
ABSTRACT: An intelligent roll for sheet and roll cover temperature profiles is a mechatronic system consisting of a roll in a web handling machine that is also used as a transducer for sensing cross-machine direction (CD) profiles. The embedded temperature sensor strips are mounted under or inside the roll cover, covering the full width of the roll’s cross-dimensional length. The sensor system offers new opportunities for online temperature measurement through exceptional sensitivity and resolution, without adding external measurement devices. The measurement is contacting, making it free from various disturbances affecting non-contacting temperature measurements, and it can show the roll cover’s internal temperatures. This helps create applications that have been impossible with traditional technology, with opportunities for process control and condition monitoring. An application used for process analysis services without adding a roll cover is made with “iRoll Portable Temperature” by mounting the sensor on the shell in a helical arrangement with special taping. The iRoll Temperature sensors are used for various purposes, depending on the application. The two main targets are the online temperature profile measurement of the moving web and the monitoring of the roll covers’ internal temperatures. The online sheet temperature profile has its main utilization in optimizing moisture profiles and drying processes. This enables the removal of speed and runnability bottlenecks by detecting inadequate drying capacity across the sheet CD width, the monitoring condition of the drying equipment, the optimization of drying energy consumption, the prevention of unnecessary over-drying, the optimization of the float drying of coating colors, and the detection of reasons for moisture profile errors. This paper describes this novel technology and its use cases in the paper, board, and tissue industry, but the application can be extended to pulp drying and industries outside pulp and paper, such as the converting and manufacture of plastic films.
Journal articles
Magazine articles
Kraft recovery boiler operation with splash plate and/or beer can nozzles — a case study, TAPPI Journal October 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.