New innovations have been put in operation for collection and handling systems of noncondensable gases (NCGs) in modern kraft pulp mills. This work investigates technologies in new pulp mills that aim to achieve the benefits of odor-free processes while enhancing chemical circulation within the mill. It describes and discusses both past and current systems for collecting and handling NCGs. The mills studied have designed and implemented their NCG systems within the past 10 to 15 years. New innovations have emerged, offering promising methods to further reduce occasional sulfurous odor emissions from the kraft process. These methods explore pretreatment and sulfuric gas stream reuse options in process units where these gases are generated or during the transportation of these side streams to their final destruction site. Using modern practices outlined in this paper, malodorous gases can be collected to the extent that a kraft pulp mill is essentially odor-free pending operator errors or major equipment malfunctions. One of the difficult aspects is that NCG systems in kraft mills are often designed case-by-case, as well as by various equipment vendors and with varying numbers of destruction sites. The actual detailed design depends on the chosen layout, process configuration depending on individual equipment purchased, and even on the design practices of individual suppliers.
This Special Paper Physics Issue of TAPPI Journal serves as a critical bridge between the phenomenological observations shared at the last International Paper Physics Conference in Wuppertal, Germany, and the rigorous quantification required to realize the “Digital Twin” paradigm. This paradigm involves the creation of a virtual dynamic representation of a process that acts as a real-time counterpart of the actual one. We are particularly indebted to Jaan-Willem Simon of the University of Wuppertal, whose leadership was pivotal in translating the conference’s academic rigor into this scholarly collection.
In a kraft pulp mill, the rotary lime kiln is responsible for converting calcium carbonate (CaCO3) into calcium oxide (CaO) to be reused in the causticizing plant. An important parameter of the calcination efficiency and the product quality is the amount of CaCO3 not converted to CaO, commonly defined as residual carbonate. This parameter is usually determined through laboratory analysis, which introduces delays in process control and limits the ability to make timely operational adjustments. This work presents a predictive model that functions as a soft sensor for the residual carbonate in a lime kiln of a Brazilian kraft pulp mill. This model was able to estimate residual CaCO3 every 30 min using routinely measured online process variables, which is a considerable reduction from the 6-h average laboratory measurement. The correlation coefficient (r) between the model predictions and the mill values was 0.83, with a mean absolute error (MAE) of 0.33%. Considering the effect of the residence time throughout the lime kiln proved to be decisive in obtaining a satisfactory prediction result. After model validation, a variable importance analysis showed that the carbon monoxide (CO) concentration in the stack flue gas (in ppm), secondary air temperature (in oC), and fan speed (in %) were the most influential variables in predicting the residual carbonate content. Combined with commonly used operation expertise, this subset of variables can serve as additional information to achieve smoother lime kiln operation. Application: The model developed in this study demonstrates how routinely available process data can be used to estimate residual carbonate in an industrial lime kiln, providing a basis for operational assessment and further development of soft-sensing approaches in pulp mills. This can help better manage fuel efficiency, operational stability, carbon dioxide (CO2) emissions, CaO quality, and residual carbonate content.
Market demand for barrier coated packaging paper and paperboard has been on a steady rise and is forecasted to further increase. As a result, there is a continued interest in improving barrier coating functionalities, which is currently an active area of investigation. In this work, a multi-layer approach was adopted that involved applying a biowax emulsion, latex, or a combination of biowax and latex top coating layer onto the kaolin/latex (20/80, 50/50, 65/35, or 70/30) precoated solid bleached sulfate (SBS) paperboard. Our main objective was to demonstrate the effect of these top coating layers on various barrier properties, especially water vapor transmission rate (WVTR) at high relative humidity (RH) and high temperature (90% RH; 38 degrees C), known as tropical/jungle test conditions. While the top coat with latex and/or biowax showed dramatic improvement in both water resistance (Cobb) and WVTR, the biowax coating increased contact angle significantly compared to the latex top coat. Contact angle increased from about 65 degrees for the latex top coat to as high as 96 degrees for the biowax top coat. Generally, it is much more difficult to improve WVTR at the jungle conditions below 100 g/m(2)/day, even with the high aspect ratio platy pigment. However, using the coating strategies adopted in this study, we were able to achieve WVTR values notably below 50 g/m(2)/day at the tropical test conditions, as well as significant improvements in regard to fold crack barrier integrity at high kaolin clay usage. Application: The findings presented in this study highlight the importance of maintaining a high degree of water resistance in barrier coatings when targeting extremely low WVTR values under severe atmospheric conditions. A multi-layer coating approach was employed in which a platy pigment (kaolin) in the base layer and a biobased wax in the top layer partially, yet significantly, replaced synthetic latex to enhance barrier performance while supporting sustainability objectives. This work provides a practical framework for advancing more sustainable barrier coating systems without compromising performance.
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 -> infinity. 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 = G(max)). 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.
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 degrees 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. Application: This paper describes the natural aging and degradation of a sustainable oil and grease barrier coating: starch-wax emulsion on two different base papers. We studied the main chemical and physical changes in this common oil and grease barrier coating at intervals of 0, 15, 90, 180, and 240 days.
The transition to 100% biobased packaging presents considerable challenges, particularly in the development of a petroleum-free barrier. Generally, biobased barriers exhibit lower flexibility compared to traditional barriers, thereby increasing the risk of cracking during the converting process. The present study examines the possibility of optimizing the substrate to reduce cracking in brittle barriers. Five three-ply composites were fabricated using commercial paperboard to enable a composite with different fiber orientation in the individual plies. The different orientations achieved varying mechanical properties, including strain-at-break and folding resistance, with a ranking that is comparable to a standard multi-ply paperboard. The composites were subjected to creasing at five distinct depths to assess the area percent of barrier cracks across the crease bead. Micro-cracks appeared on the surface before larger coating cracks were registered. As expected, the area percent of barrier cracks increased significantly with greater creasing depths. The orientation of the bulky middle ply showed little difference in the cracking propensity. However, by replacing the stiffer bottom ply with a ply of lower stiffness, the cracking propensity was significantly reduced without a substantial loss in mechanical properties. Hence, these findings indicate that it is possible to reduce the cracks in the barrier by modifying the fiber orientation in the different plies. Application: The present research provides an avenue for working with paperboard properties that enables bio-based barriers.
Fiber-based materials used for foodservice, takeaway, and other packaging applications must typically provide water and grease resistance. Simultaneously, there is growing interest towards bio-based and renewable barrier coatings. In this study we applied thermoplastic long chain fatty acid cellulose esters onto paperboard using electrostatic powder coating to create barrier properties of interest. Electrostatic powder coating provides a water-free process to tackle moisture-induced quality issues and to provide an even coating layer. Cellulose octanoate and palmitate esters were produced in pilot scale. These were ground into fine particles using liquid nitrogen and applied onto paperboard sheets using an electrostatic powder gun. The loosely packed coatings were fixed and fused onto the paperboard by hot pressing. We characterized the coated sheets for coating thickness, contact angles with water, water absorption, grease resistance (KIT), and olive oil barrier. Two commercial polyethylene powders were used as references. Our results indicated that the long chain cellulose fatty acid ester coatings were thermoplastic and hydrophobic with contact angles above 100 degrees. Water absorption was similar to the reference coatings. While grease resistance was lower than with the references, the cellulose ester coatings slowed down diffusion of olive oil through the paperboard. Cellulose octanoate ester with a lower melt viscosity already provided smooth coatings after the initial hot pressing step, while in most cases, the second post hot pressing step further improved the barrier properties. Application: This paper presents a method for creating water and grease resistance utilizing a combination of cellulose grafted with long chain fatty acids and electrostatic powder coating. This approach can be used for different fiber-based packaging materials, especially when tackling moisture-induced quality issues and aiming at even barrier coating layers.
Increasing the competitiveness of the pulp and paper industry requires an effective optimization of its existing assets in line with a long-term vision for process transformation, production upgrade, and product diversification. Currently, pulp production increase is one of the main sources of additional revenue for the kraft industry. Likewise, energy efficiency is often employed as a cost-effective approach to reduce operating costs, enhancing the possibilities to lower fossil fuel consumption and contributing to a low-carbon economy. On the other hand, reaching higher production targets and facilitating process transformation, such as biorefinery implementation, heavily depend on the status and performance of a mill's current infrastructure; therefore, a system analysis is needed to assess the new production requirements, the bottlenecks, and the interactions across departments. In order to obtain practical improvement solutions, direct and indirect impacts on process performance and resource utilization should be considered. This work provides an overview of the key challenges that need to be addressed for production increase and energy efficiency improvement. The methodology starts by a scope analysis for debottlenecking and screening capacity limitations vs. mill targets, followed by their ranking (bottleneck ranking diagram). Benchmarking, gap analysis, and root-cause techniques are applied to diagnose system inefficiencies. This mill-wide debottlenecking assessment is then used to guide the selection of a long-term sustainable operation and design a portfolio of improvement projects by avoiding cross effects of the short-term projects on the long term. A case study of a kraft pulp mill is used to illustrate the proposed methodology.
Recent advancements in our ability to evaluate papers and our understanding of the mechanics of box failure have brought a renewed focus on measuring the performance of corrugated medium and an associated evolution of paper measurement approaches. This study evaluates the load curves, Hardness (where the fluted structure's loading shifts away from an elastic response), and Concora medium crush test (CMT) values for a range of corrugated mediums in different common flute geometries. The shape of the load curve is a function of the geometry of the fluting profile and the relative stiffness of the paper, with smaller flutes and heavier papers reaching both the Hardness value and the ultimate load at lower deformation. Nonetheless, while the specific dynamics during the loading process vary, Hardness and CMT values correlate linearly between flute structures, even when testing specimens after different equilibration periods post-fluting. These correlations confirm the applicability of the standard A-flute CMT test to a broad range of papers and potential combined board flute structures, supporting quality assurance processes for medium production and optimization in corrugated board manufacturing. Application: Given the proliferation of test methods assessing corrugating medium, this work helps those measuring paper performance understand how the different tests may relate in order to help focus the properties that a researcher or quality department may need to assess.
To meet the need to further improve thermal efficiency and environmental performance of kraft pulp mills, new systems and techniques have been developed within the evaporation plant. This paper describes these novel approaches and how they were implemented in a project completed in 2018 for a new evaporator and condensate treatment system supplied by Valmet at the SCA & Ouml;strand market pulp mill in Sweden. This project was part of a stepwise upgrade of the complete mill to increase the production capacity of the mill from 430,000 to 900,000 air-dried metric tons/year (ADt/y). As part of this upgrade, the mill had the objectives to increase the energy efficiency of the pulp mill and to minimize the air emissions as much as possible, the effluent volume, and the water usage in the mill. The mill also wanted to have the disposal of the biosludge in the black liquor, and the production of tall oil from black liquor soap, liquid methanol, and turpentine. This required that the new evaporation and condensate treatment system be very closely integrated into the other process departments of the mill, including integration of the hot weak black liquor flash vapor from the digester directly into the evaporator train and the production of multiple streams of clean evaporation plant condensate at the correct temperature for the bleach plant. Heat and mass balance calculation values, which were found to do very well in predicting the effect on actual mill operation, are also presented in this paper. Application: This study provides a benchmark example of how a high level of process department integration can be achieved to obtain a very high level of energy efficiency and environmental performance in an actual kraft pulp mill environment, while addressing corresponding technical challenges. It also illustrates that optimizing energy efficiency and condensate production in the evaporation plant requires focusing on lowering the overall mill steam consumption and not just on improving the steam economy of the evaporation plant itself.
Vapor retarders, crucial in building constructions, are traditionally made from plastic-based materials, raising environmental concerns due to the use of fossil materials. This study explores the potential of functionalized papers, particularly silica-paper hybrids, as sustainable alternatives. This work delves into the moisture properties of sol-gel coated linter papers, considering the water vapor permeability and physisorption behavior following DIN EN ISO 12572 and DIN EN ISO 12571. The study addresses hysteresis, noting the lower hysteresis of mesoporous coatings in comparison to dense coatings and implying benefits in moisture release. Findings underscore the need for a nuanced understanding of coating characteristics and their impact on sorption. In order to better assess the relationship between the coating content of the papers and their specific sorption properties, further investigations, such as the measurement of specific surface properties (e.g., specific surface area), are required. The findings of the water vapor diffusion resistance measurement study demonstrate a correlation between the observed resistance and the vapor levels. The results show that the water vapor diffusion resistance is elevated at lower vapor levels when compared to higher levels. This particular material behavior is typically employed within the construction industry for the utilization of moisture-variable water vapor retarders. The silica-paper hybrids exhibit a response that indicates the potential for advancement into a moisture-variable water vapor barrier. Application: This research on silica-paper hybrids is a first step towards the application of paper materials in building construction as moisture regulating layers.
Delamination strength is an essential property for the creasing and folding operations of paperboard into boxes. Due to fixation during creasing, the paperboard suffers in-plane straining. In the present study, we aim to increase our understanding of how in-plane straining affects the delamination properties of paperboard. Samples of paperboard were first strained in in-plane tensile loading, both in the machine-direction and in the cross-direction. Afterward, the paperboard is loaded in the out-of-plane (ZD) direction. Three different grades of commercial paperboard from two major manufacturers were tested in a climate-controlled lab. The results showed similar results for all grades of paperboard, with the delamination strength and the out-of-plane stiffness decreasing virtually linearly with pre-straining. With about 5% plastic in-plane straining, the strength was reduced by about 20% and the stiffness decreased by more than 50% for all grades of paperboard. Normalizing the strength and the stiffness with their values without pre-straining reveals virtually the same relation for all grades of paperboard. If proven to be a general result, this will prove valuable in reducing the demand for experiments. Application: The results from this study are important for the understanding and modeling of creasing and folding of paperboard.
Paperboard packaging is made by processing board materials into sheets or rolls and shaping them through creasing, cutting, folding, and erecting. The conversion process generates residual moments at the folds that cause panel bulging. This study experimentally investigates how the bulging introduced during the converting processes influence the mechanical response of paperboard packages during point load testing within the elastic deformation range. The study shows that panel bulging may significantly affect packaging performance as-perceived strength and stiffness. Bulging, influenced by the board's basis weight, can affect the package performance even more than packaging stiffness. Point load tests in the elastic region were performed on empty packages (78 mm & times; 50 mm & times; 110 mm) with force applied at specific points along their long sides. The packages evaluated in this study were made of two identically processed materials of different grammages. The heavier material showed more pronounced bulging than the lighter one, leading to overlapping force-displacement curves for the packages, and to that, a lower force and stiffness may be measured at a certain indentation depth for the package of heavier material. This complicates material choice according to functional requirements. The results show that a highly bulged package might resemble one with less bulging of another material. According to the results, it is not certain that a higher grammage package shows a higher indentation force and stiffness than a lower grammage package when measured at a certain indentation. This indicates that optimizing the creasing and folding processes can be a way to enhance performance rather than simply increasing board weight. The study underscores the importance of controlling converting parameters, especially creasing and folding behavior. Well-performed creasing and folding gives a low residual momentum, little bulging, and a high stiffness and compression strength at point loading in the elastic region. Proper optimization can improve packaging performance and manual handling user-friendliness. Application: The results from this study are of significant importance for the package industry, especially in package design, as the results show that a lower grammage may give a higher stiffness, depending on loading position.
Micro-computed tomography (& micro;CT) has a reputation as a nondestructive analysis method. Unfortunately, this leads to the common misconception that radiation damage of the sample does not play a role. With the increased use of & micro;CT in laboratory-based machines, more and more cellulose-based materials are studied. In this paper, we show with three examples that radiation damage is important in dry and wet paper and in viscose fibers. In an attempt to quantify radiation damage, we came up with a workflow that enables researchers to predict the X-ray dose within a laboratory-based & micro;CT machine. This gives researchers the possibility to quantitatively judge the influence of radiation damage on each measured sample. While one cannot extend the measured doses from one machine to another, one can still apply the work flow presented in this study to any & micro;CT setup. In this way, it is possible to minimize radiation damage by choosing the best parameters in a & micro;CT for obtaining perfect data with no or little radiation damage. Application: Radiation damage occurs quite often in & micro;CT measurements. In this work we show how the X-ray dose can be estimated and then used to optimize the & micro;CT parameters to get both, high quality data and little-or-no radiation damage.
In this study, an in-depth exploration of filled paper was conducted to understand its structural and permeability characteristics. Cotton linter pulp and precipitated calcium carbonate (PCC) filler were utilized to prepare pure fiber paper, and PCC1 and PCC2 filled papers with different filler particle sizes. Then, the pore structure parameters of paper samples were characterized by mercury intrusion porosimetry, and the X-ray computed tomography (X-CT) scanning was carried out. Subsequently, the 3D microstructures were established based on the X-CT slice images, and the filler characteristic parameters and filler 3D distribution were quantitatively analyzed. Finally, permeation simulations in the thickness and horizontal directions were performed. The findings indicate that filling changes the paper porosity, and the pore tortuosity varies with direction. The estimated pore-throat radius distribution shows specific patterns for different papers. The fillers have different distribution characteristics in the paper samples. Moreover, the paper permeability differs with direction, with small-sized filler having a significant impact on fluid penetration in the thickness direction. Overall, this study provides an effective method for investigating internal paper filler and its distribution, which contributes to the understanding of paper structure-performance relationships. Application: This research offers an effective exploratory approach for investigating paper fillers from the perspective of computer simulation, facilitating the structural design and performance optimization of paper-based functional materials.
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 complaints, 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 compounds, 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 methyl mercaptan. 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 communities 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. Application: This study investigates the role of microbes in odor issues in papermaking by analyzing process water from two recycle paper mills using Illumina sequencing. The literature study of the identified microbes reveal that some microbes are responsible for generating odor-causing compounds, including volatile organic compounds (e.g., haloanisoles, geosmin) and sulfur compounds (e.g., hydrogen sulfide, methyl mercaptan), whereas others contribute to biofilm and slime formation and other functional processes. By understanding the roles of the identified microbial communities, this research provides a foundation for developing targeted strategies for effective odor control and improved microbial management in papermaking.
Rotary lime kilns are essential and complex components in pulp mills using the kraft process. They are primarily used to produce lime (CaO), which is then employed to make white liquor, the reagent used to separate wood fibers. To understand and improve the performance of the kiln, modeling its behavior is essential. However, the kiln operates through a complex combination of thermal and chemical phenomena. That is why a simplified approach was used to tackle this challenge. A zero/one-dimensional steady-state analysis was performed based on first principles to simplify the modeling process and reduce the need for experimental data. Additional assumptions, such as steady-state operation and the absence of a refractory lining, were introduced to further simplify the model so that it can be used for daily analysis. Moreover, the auxiliary equipment of the plant, such as the intercooler and preheat cyclone, is also modeled. The final model was validated using data from the literature and a two-month analysis of experimental measurements from the Burgo Ardennes lime kiln in Virton, Belgium. It shows good agreement with the available data, with a 6% deviation for the adiabatic flame temperature and a 17% average error in predicting the kiln shell outside temperature. For the fuel and lime flow rate predictions, also validated over the same two-month period, the errors were -6.6% and 0.6%, respectively. Application: This model provides pulp mill operators and engineers with a simplified tool to monitor the complete lime kiln performance and detect operational deviations.
The physico-mechanical and ethylene scavenging properties of active packaging consisting of paper prepared from bamboo (Bambusa vulgaris) fibers loaded with varying concentrations of nano titanium dioxide/ cuprous oxide (TiO2/Cu2O) composite was investigated for its ability to delay ripening of Philippine climacteric fruits. Tests of paper containing 1% to 5% TiO2/Cu2O showed no or limited negative impact on its physical, optical, and mechanical properties. Images from a field emission scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (FESEM-EDS) showed dispersion and agglomeration of TiO2/Cu2O nanoparticles on the paper surface. The percent weight of titanium and copper increased with increasing metal oxide composite concentration used in this study. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy indicated small shifts in band intensity at 3330 cm-1 and 1100 cm-1 in the hydroxyl (O-H) and C-O regions, respectively, suggesting possible chemical or physical interactions between the metal oxide and paper. Contact angle measurement suggested that TiO2/Cu2O nanoparticles may have imparted paper hydrophobicity at 3%-5% concentration, possibly through increased microscale roughness. The ethylene scavenging experiment indicated that there was a significant delay in the ripening process of mango and tomato when packed in paper doped with 3% and 5% TiO2/Cu2O. The fruits were greener with a firmer texture compared with untreated control after three days of storage under natural light and ambient condition. The preliminary results suggested that 3%-5% TiO2/Cu2O active packaging modification can remove ethylene from the fruit's storage environment, extending shelf life and maintain quality for three days. This simple technique could have potential economic benefits for the fruit industry by directly reducing post-harvest waste, and the delayed ripening could provide flexibility in supply chain management.
Innovation in packaging design will be facilitated by a simple test method to indicate whether a product is compatible with paper recycling. Three laboratories cooperated on the development of a method and used it on linerboard, coated paperboard, wet-strength paperboard, and white copy paper. This test method includes pulping and screening. The data presented here illustrate the factors affecting the results of a bench-scale test. Our observations show that a bench-scale test can give reproducible results for yield, < 5%. We also present an approach to contaminant assessment based on current published test methods. A specification with a lower limit on yield of 70% and a contaminant level of less than 5,000 particles/kg is proposed. Application: The purpose of this work is to provide a validated test method for determining yield during recycling of packaging materials.
