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Review of coating cracking and barrier integrity on paperboard substrates, TAPPI Journal November 2022
ABSTRACT: Barrier packaging formats are major growth areas for the pulp and paper industry. It is technically challenging to maintain barrier properties during converting and end-use applications. Improved manufacturing capabilities and coating formulation knowledge will help maintain barrier integrity and enable growth of barrier products in challenging applications. These improvements will accelerate product development and commercialization, and allow faster response to product performance issues such as cracking. The literature on coating cracking provides knowledge mostly on the effects of coating formulations and to a lesser extent on substrate effects. Despite a large number of publications dedicated to coating failures, the approach to improve coating cracking remains empirical, and the transferability between studies and to real life applications has not been well established. Model development that successfully predicts commercial performance is in its infancy. However, some of these simplified models do a fairly good job predicting experimental data. The current work reviews the state of understanding as regards coating and barrier cracking and highlights the need for more research on cracking and barrier integrity.
Journal articles
Magazine articles
Modeling the influence of rheology on smooth rod coating systems, TAPPI Journal November 2022
ABSTRACT: Rod coating methods are of interest for the application of barrier coatings, especially at off-line facilities that may run at moderate speeds and narrow web widths. At lower line speeds and lower coating solids, it is difficult to achieve good coat weight control because of poor loading of the rod. While there is extensive literature available about blade and roll coating, there seems to be less reported on the rod loading of smooth rods to obtain various coat weights. Much of the work is around metering rods working on applicator rolls at high speeds that are associated with the metered size press, with a focus on ribbing instabilities. This work employs a simplified model, neglecting some complex features of rubber deformation and film split, to estimate the influence of the process parameters such as speed, rod diameter, viscosity, and rod loading on the coat weight obtained. As found in practice, at low speed and low viscosities, the coat weight-load curve is steep, leading to poor control of the coat weight and coat weight uniformity. If the viscosity is increased, the curve is modified, and control is possible with rod loading in a normal range. For shear thinning fluids described by the Carreau model, the power law index and other parameters need to be in the correct range to obtain the desired effect. Modeling predictions show a steeper dependence of coat weight with rod pressure when compared to pilot coater data. This may be caused by missing details in the mechanical loading of the rod related to tube pressure or from neglecting the impact of filter cake formation of the applied coating in the model.
Journal articles
Magazine articles
Coatings for sustainable paper-based flexible packaging: Barrier properties and processability, TAPPI Journal November 2022
ABSTRACT: In this study, the use of waterborne barrier dispersions from trademarked BLUEWAVE Mechanical Dispersion Technology as thin coatings for paper-based flexible packaging was investigated. Prototypes were designed and examined for their performance in process, rheology, barrier, heat-seal/hot-tack, and coefficient of friction (CoF). Compositional details such as the type and amount of base resins and dispersants were found to significantly impact performances and were key to the development of new prototypes that deliver the performance profiles for implementation in paper-based flexible packaging applications.
Journal articles
Magazine articles
Novel test method for measuring defects in barrier coatings, TAPPI Journal November 2022
ABSTRACT: In the last several years, activity to develop water-based barrier coatings (WBBCs) that meet challenging packaging performance requirements has increased dramatically. Cellulose-based packaging solutions can provide a more sustainable packaging option for replacing single-use plastic-based options like extrusion-based and laminated materials. An advantage of WBBCs is the opportunity to reduce the coating thickness applied, as long as the barrier requirements can be met. A challenge that must be overcome is the ability to maintain a defect and pin-hole-free coating layer after coating and drying to retain the barrier performance. Many formulation and coating parameters can affect the barrier coating layer quality; however, methods for detecting more subtle differences in these types of studies are not widely available. Work was carried out to develop a quantitative technique for detecting and measuring the quantity and size of defects in the barrier coating layer. A test method has been developed using a combination of dyed oil and image analysis to be able to characterize the imperfections in the coating surface. The use of dyed oil serves two purposes. First, it better simulates the types of materials, in this case, oils and grease, for which the barrier coating is expected to hold out. Second, it also provides contrast between the coating and failure points for testing. An image analysis technique is employed to characterize the number and size of the imperfections. For the former, it reduces the testing time required if a quality control or laboratory technician counts the dots. For the latter, it assists with judgment on the source of the root cause of the imperfection, such as base sheet defects, coating dispersion issues, or perhaps micro-blisters in the coating, as some examples.To show the benefit of this technique, several pilot coating studies were designed to see if the new technique could be utilized to detect differences in WBBC performance. Both process and chemical variables were evaluated. With refinement, it is believed this technique can be utilized in development work, as well as for a potential quality control technique for manufacturing of coated paper and paperboard products.
Journal articles
Application of Spherical Hollow Calcium Carbonate Particles
Application of Spherical Hollow Calcium Carbonate Particles as Filler and Coating Pigment, 2002 Coating Conference Proceedings
Journal articles
A systems approach for process debottlenecking towards a sustainable pulp and paper industry, TAPPI Journal April 2026
ABSTRACT: 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.
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.
Journal articles
Permeability simulation for filled paper based on three-dimensional structural model developed by X-ray computed tomography scanning, TAPPI Journal March 2026
ABSTRACT: 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 smallsized 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.
Journal articles
Moisture performance of silica-paper hybrids in the hygroscopic range, TAPPI Journal March 2026
ABSTRACT: 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.
Journal articles
Effects of in-plane straining on the out-of-plane delamination properties of paperboard, TAPPI Journal March 2026
ABSTRACT: 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.