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In this research we proposed and tested a solution for improving lightfastness of paperboard electrophotographic prints – enhancing the printed material with inks containing pearlescent pigments. The goal was to analyze how pearlescent pigments' composition and the size of their particles affect lightfastness, and to assess whether this important property is influenced by the tone value of the initial ink layer. Therefore, lightfastness of the unprinted paperboard and the paperboard printed in electrophotography with medium and full coverage of black ink was measured before and after overprinting with pearlescent inks. The results indicate that pearlescent pigments can be efficiently used to prevent light induced degradation of both paperboard and the corresponding prints. The most significant improvements in lightfastness were noticed when pearlescent inks were printed directly onto the paperboard and on the prints with 50 % black coverage. The best protection from light was achieved with pigments containing only two layers – mica and ferric oxide. Pigments containing mica, titanium dioxide, and tin oxide provided satisfactory lightfastness of the printed paperboard even with the small surface coverage. No significant correlation was found between the size of pearlescent pigment particles and the lightfastness of the paperboard prints to which they are applied. [ABSTRACT FROM AUTHOR]

This study investigated the use of sodium carbonate pulping in oil palm empty fruit bunch (OPEFB) pulp production for paperboard manufacturing. The pulping varying the active alkali (AA) (4.5 %, 6.5 %, 8.5 %), NaOH fraction (F) (10 %, 20 %, 30 %), and cooking time (T) (30′, 60′, 90′). The performance was evaluated based on screened pulp yield, kappa number, and delignification selectivity. Furthermore, the functional groups, S/G ratio, and morphological structure of the optimum pulp were observed. The tensile and tear indices of the OPEFB pulp paperboard were also measured. The results suggest sodium carbonate pulping at a low chemical dose successfully produced OPEFB pulp. Based on the highest delignification selectivity value of 12.74, the most effective pulping conditions were achieved with AA-6.5 %, F-30 %, and T-90′. The optimum OPEFB pulp analysis revealed a decrease in lignin proportion with the dominant degradation of the syringyl unit. Thus, the fibers are easily separable during mechanical treatment. These characteristics influenced the paperboard, resulting high tensile and tear indices of 7.90–8.15 Nm g−1 and 15.09–16.25 mN m2 g−1, respectively. Overall, this study demonstrated the potential of sodium carbonate pulping to produce high-quality pulp and paperboard from OPEFBs, highlighting the thoroughness of the research process in the pulp and paper manufacturing field. [ABSTRACT FROM AUTHOR]

Thermoforming of fibre‐based materials faces challenges due to their restrictive three‐dimensional formability and lack of compatibility between material properties and traditional thermoforming methods. Treatment techniques present an intriguing area of research to address the gap between material characteristics and process requirements. Therefore, this study examined the influence of inline steam treatment on the thermoforming of plastic‐coated fibre‐based materials with different product geometries. Three plastic‐coated paperboards were subjected to thermoforming, with and without steaming, and their thermoformability was assessed based on the maximum depth and draft angle of the samples. Following 7 s of steaming, the materials exhibited a moisture content 2–4 percentage points higher than that of the original setup, yielding a greater curling rate in the produced samples across different geometries. The curling rate was influenced by the tensile stiffness of the materials and was correlated with the size of the flat‐edge area in the studied geometries. Furthermore, findings revealed varying rates at which steaming affected different geometries. Steaming substantially enhanced the achieved depth for geometries where the material was incapable of reaching the mould without moisturization, particularly observed for smaller geometrical shapes. This improvement was linked to steaming, which enhanced pliability, facilitated material penetration, and increased the final depth. However, in geometries where the material could reach the mould without moisturization, steaming expanded the contact area but could also result in a greater spring‐back rate and reduced depth, potentially owing to the loss of elastic modulus by moisturization. Nevertheless, the rate of spring‐back did not consistently increase with steaming and could be influenced by various material‐related factors, including the properties, composition, preparation methods, and postforming drying. Despite depth changes, steaming consistently improved the obtained draft angles, indicating that the materials were drawn more efficiently to the sidewalls across all instances studied. Thus, this study underscored the importance of choosing appropriate materials and moulds for hydrothermal moisturization treatments in the thermoforming process. [ABSTRACT FROM AUTHOR]

The disposable cup market has long relied on paperboard with a fossilbased polymer coating as a replacement for 100% plastic cups. Paperboards with biobased or biodegradable polymer coatings are aimed at reducing the fossil resource consumption of the packaging sector. However, as their properties are inherently different from traditional, fossilbased materials, they can face runnability issues. In order to establish a connection between certain material properties and runnability issues, four coated paperboard materials with differing surface and strength properties were converted into 250 mL/8 oz disposable drinking cups. The materials included two single-side extrusion-coated paperboards and two two-sided dispersion-coated paperboards. The cups were manufactured in two separate runs with minor machine adjustments to affect the resulting cup geometry. A comparison of the manufactured cups and material properties revealed the materials' coefficient of friction to be the major cause of runnability issues or defects. Other suspected properties affecting the performance of cup materials included bending stiffness and compression strength. [ABSTRACT FROM AUTHOR]

The disposable cup market has long relied on paperboard with a fossil-based polymer coating as a replacement for 100% plastic cups. Paperboards with biobased or biodegradable polymer coatings are aimed at reducing the fossil resource consumption of the packaging sector. However, as their properties are inherently different from traditional, fossil-based materials, they can face runnability issues. In order to establish a connection between certain material properties and runnability issues, four coated paperboard materials with differing surface and strength properties were converted into 250 mL/8 oz disposable drinking cups. The materials included two single-side extrusion-coated paperboards and two two-sided dispersion-coated paperboards. The cups were manufactured in two separate runs with minor machine adjustments to affect the resulting cup geometry. A comparison of the manufactured cups and material properties revealed the materials’ coefficient of friction to be the major cause of runnability issues or defects. Other suspected properties affecting the performance of cup materials included bending stiffness and compression strength.

The potential of paper and paperboard as fiber-based materials capable of replacing conventional polymer-based materials has been widely investigated and evaluated. Due to paper’s limited extensibility and inherent heterogeneity, local structural variations lead to unpredictable local mechanical behavior and instability during processing, such as mechanical forming. To gain a deeper understanding of the impact of mechanical behavior and heterogeneity on the paper forming process, the Finite Element Method (FEM) coupled with continuum modeling is being explored as a potential approach to enhance comprehension. To achieve this goal, utilizing experimentally derived material parameters alongside stochastic finite element methods allows for more precise modeling of material behavior, considering the local material properties. This work first introduces the approach of modeling heterogeneity or local material structure within continuum models, such as the Stochastic Finite Element Method (SFEM). A fundamental challenge lies in accurately measuring these local material properties. Experimental investigations are being conducted to numerically simulate mechanical behavior. An overview is provided of experimental methods for material characterization, as found in literature, with a specific focus on measuring local mechanical material structure. By doing so, it enables the characterization of the global material structure and mechanical behavior of paper and paperboard.

The characterization and modeling of the out-of-plane behavior of fiber-based materials is essential for understanding their mechanical properties and improving their performance in various applications, especially in the forming process. Despite this, research on paper and paperboard has mainly focused on its in-plane behavior rather than its out-of-plane behavior. However, for accurate material characterization and modeling, it is critical to consider the out-of-plane behavior. In particular, delamination occurs during forming processes such as creasing, folding, and deep drawing. In this study, three material models for paperboard are presented: a single all-material continuum model and two composite models using different cohesion methods. The two composite models decouple in-plane and out-of-plane behavior and consist of continuum models describing the behavior of individual layers and cohesive interface models connecting the layers. Material characterization experiments are performed to derive the model parameters and verify the models. The models are validated using three-point bending and bulge tests and show good agreement. A case study is also conducted on the application of the three models in the simulation of a deep drawing process with respect to wrinkle formation. By comparing the simulation results of wrinkle formation in the deep drawing process, the composite models, especially the cohesive interface composite model, show greater accuracy in replicating the experimental results, indicating that a single continuum model can also be used to represent wrinkles. [ABSTRACT FROM AUTHOR]

Tensile properties of paperboard have been characterized, and it has been shown that paper tensile properties are dependent on the strain rate. Tensile testing was done using strain rates in the range 10−4–3 s−1, which corresponds to crosshead movements ranging from 1 up to 24,000 mm/min, using an electro-mechanical testing machine. Two paperboards, and its free-laid top, middle and bottom plies were characterized in MD and CD. The testing was limited by the maximum crosshead speed of the testing machine. Initially 50 mm (grip to grip) long samples were tested, but to test even higher strain rates also short samples with length of 5 mm were tested. The results showed that ultimate strength increased by 9 % per decade increasing of testing rate, and Young's modulus increased by 7 %. This shows that the previously reported rule of thumb of 10 % increase of in-plane strength per decade increase of strain rate holds. The testing here shows that this is valid also at strain rates as high as 3 s−1. Moreover, the strain at break in CD for long tensile specimens was observed to decrease when the strain rate exceeded 0.1 s−1, which resulted in straighter crack paths. [ABSTRACT FROM AUTHOR]

Modern μ -CT scans offer non-destructive three-dimensional microstructure analysis of various materials. Despite small density contrasts, this technology also accurately captures the complex network structure of paper and paperboard. It provides detailed insight into the fiber orientation distribution in paper, which was previously unattainable with existing measurement methods. The image analysis results are applicable for numerical fiber network models, and simulations based on these models can significantly improve our understanding of the microstructural influence on macrostructural paper properties, such as strength, stiffness, and curl tendency. This work presents a new method for investigating the microstructural fiber orientation in paperboard. Orientation tensors obtained from μ -CT scan image processing are extracted and evaluated. Based on the direction of the orientation tensor's first eigenvector, the fiber orientation distribution is determined and then approximated by periodic and non-periodic probability density functions (PDFs). In this study, 40 commercial paperboard samples, each consisting of three plies, were analyzed. From a given set of commonly used PDFs, the best fitting ones have been identified based on their original location in the paper roll and on their ply. It was found that the von Mises PDF provided the most accurate representation of fiber orientation distribution in the middle ply, while the Elliptical PDF was the most suitable for the outer plies. Moreover, a more pronounced fiber orientation anisotropy was observed at the edges of the paper roll than in its center. The best PDFs and their function parameters are provided to allow for direct usage in numerical microstructure models of paperboard, thus enhancing their representativeness. [ABSTRACT FROM AUTHOR]

Cellulosic material is considered to be excellent for food packaging due to its low cost, easy degradability, and high recyclability rates. However, its application is still limited due to its porous structure and high hydrophilicity, which provide high permeabilities to grease, gas and water vapor. One solution to fix these issues and to bring new functionalities that can also extend food shelf life is to coat the paper substrate with biopolymers containing nanoparticles and/or components with antioxidant and/or antimicrobial activities. In this regard, the aim of this study was to review some aspects of the current knowledge critically and didactically on applications of biopolymer-based coatings incorporated with active components and/or nanoparticles on paper/paperboard materials usually applied as primary cellulosic active packaging. Studies have shown that this combination can positively improve the physical, mechanical, and barrier properties of cellulosic packaging, along with the enhancement of antioxidant and antimicrobial activities. A better understanding of these aspects enables the use of other active compounds to develop more functionality to the packaging itself as well as to apply it to food packaging in general. [ABSTRACT FROM AUTHOR]

The potential of paper and paperboard as fiber-based materials capable of replacing conventional polymer-based materials has been widely investigated and evaluated. Due to paper's limited extensibility and inherent heterogeneity, local structural variations lead to unpredictable local mechanical behavior and instability during processing, such as mechanical forming. To gain a deeper understanding of the impact of mechanical behavior and heterogeneity on the paper forming process, the Finite Element Method (FEM) coupled with continuum modeling is being explored as a potential approach to enhance comprehension. To achieve this goal, utilizing experimentally derived material parameters alongside stochastic finite element methods allows for more precise modeling of material behavior, considering the local material properties. This work first introduces the approach of modeling heterogeneity or local material structure within continuum models, such as the Stochastic Finite Element Method (SFEM). A fundamental challenge lies in accurately measuring these local material properties. Experimental investigations are being conducted to numerically simulate mechanical behavior. An overview is provided of experimental methods for material characterization, as found in literature, with a specific focus on measuring local mechanical material structure. By doing so, it enables the characterization of the global material structure and mechanical behavior of paper and paperboard. [ABSTRACT FROM AUTHOR]

Effects of two biodegradable coatings were compared relative to the characteristics of white-top linerboard. To coat the surface of the paperboard, nano-polyurethane was sprayed onto the surface using a nozzle. Subsequently, the samples were placed inside a refrigerator and freezer for a period of 2 and 4 months. In the second stage, nano-polyurethane was again sprayed onto the surface, using a nozzle, to improve the performance of the coating material. To further enhance the coating, the surfaces of the coated white-top linerboard were coated with a nanoclay using a laboratory coater. Subsequently, the samples were placed inside a refrigerator and freezer for a period of 2 and 4 months. The properties of the samples were measured thereafter. The results showed a reduction in water absorption of the samples after coating and freezing. This can be attributed to the penetration of the coating solution into the paper pores, resulting in a decrease in pore diameter and, consequently, a decrease in water permeability through the paper pores. In the coated and frozen samples, an increase in thickness and surface smoothness was observed, but most of the mechanical strength properties decreased. These changes were more pronounced in the dual-layer coatings.

Evaluation of physical and mechanical heterogeneity in commercial paperboards is needed to promote their use in structural applications, especially within the field of packaging. Understanding the range of their behaviors is needed to compete with other materials in the current marketplace and expand in others. This work describes the physical and stiffness heterogeneities of twelve commercial materials using tensile tests in the cross-machine direction and several inverse analyses. The effects of grammage, thickness, and apparent density on tensile stiffness were evaluated in both the linear elastic and nonlinear regimes. Thickness and density provided the best explanation for elastic heterogeneous behavior in most of the materials; local grammage was not the best descriptor for any material. The analyses used here were not able to provide a good explanation of the nonlinear behavior, which was attributed to the development of large shear strains within the materials as they neared failure. This work provides a methodology for additional heterogeneous behavior examinations. [ABSTRACT FROM AUTHOR]

The 2023 being on its way to be the warmest year in the 174-year global surface temperature history it is becoming more and more evident how crucial it is to break the linkage between economic growth and greenhouse gas emissions.The pulp and paper industry is highly energy intensive industry sector. It is the fourth largest industrial energy user and currently produces approximately 1.3% of global greenhouse gas emissions. While the demand for paper and paperboard products keeps rising, it is essential for the industry to find energy efficient solutions for reducing the environmental impact of the pulp and paper products. 80% of the progress in energy efficiency in Finnish paper mills is due to improved technology and more optimal operational modes. Optimizing existing processes has bigger effect on energy efficiency than closing old and starting new paper mills.Pulp refining is one of the most energy intense steps in the paperboard production, representing 15%–18% of the total energy consumption of a paper mill. The effect of a commercial cellulase enzyme product was evaluated for energy savings and avoided emissions in the refining process of a paperboard mill. Data from a paperboard line using Bleached Softwood Kraft Pulp (BSKP) from a separate pulp mill was provided by a Finnish paperboard mill containing production runs both with and without commercial cellulase product ECOPULP® R. Data was collected from the mill automation system to evaluate and compare a refining capacity restricted run and a run that was not refining capacity restricted.Analysis of the data showed a reduction of refining energy by approximately 16%–17% when the cellulase enzyme was used. This corresponds to 2 kg of CO2 emissions avoided per tonne of pulp refined when calculated using the Finnish average electricity emissions intensity in 2022. Use of the cellulase enzyme enabled the refining results that could not have been reached with the bare mechanical refining capacity of the mill.Cellulases can be efficient processing aids in pulp refining. The reduction of required mechanical refining and electrical power to run the refiners to achieve the required freeness can significantly affect the carbon footprint of the paperboard products, whereas the negative impact of emissions from enzyme production is negligible. Reduction of CO2 emissions is especially significant in the areas where the electricity mix used for the production is based heavily on fossil fuels.

A continuum damage framework is proposed for modelling the delamination process occurring in paperboard during mechanical loading. The main application of interest is line creasing and subsequent line folding used in package forming. To adequately capture creasing and folding, a continuum damage framework that uses a single isotropic damage variable that evolves with the plastic strains associated with out‐of‐plane shearing is used. The damage evolution is calibrated against folding experiments for a specific reference mesh, and a simple scaling strategy is proposed to reduce the inherent mesh dependency. To highlight the potential of the proposed model, an illustrative 3D example is considered where a paperboard sheet is creased by two plates and folded to resemble the corner of a package. [ABSTRACT FROM AUTHOR]

Advances in the three‐dimensional (3D) forming of fibre‐based materials require the formulation of more formable materials and the development of process lines, machinery, and tools. Using a thermoforming process to convert fibre‐based materials into 3D forms is an emerging area of research which requires further investigation into the practicality of the process line and tooling in forming such materials. Accordingly, this study evaluated the impact of the thermoforming process operation and tooling on the thermoformability of plastic‐coated paperboards. The main objective was to provide design recommendations for the future development of thermoforming lines, followed by guidelines for tooling design to improve the performance of materials utilising the currently available machinery. This study examined the thermoforming behaviour of two different plastic‐coated paperboards in vacuum and pressure thermoforming by investigating their maximum acquired depth, shape accuracy, and damage mechanisms. The research findings, based on the depth and linear elongation achieved, indicate that the inferior performance of plastic‐coated paperboards in thermoforming cannot be wholly attributed to restrictions in the three‐dimensional formability of materials; the inability of the current process lines to utilise the maximum potential of materials can also lead to their inferior performance. Notably, the method of pressure supply and cooling of materials requires adjustment of these materials. From a tooling perspective, owing to the spring‐back effects, the enlargement of the mould dimensions should be considered during the design stage. Additionally, based on potential opportunities with the current unmodified machinery and materials, products in the size of standard food trays have a higher likelihood of being optimised with tooling design than smaller sized shapes, which still require additional developments in materials. Moreover, designing moulds without draft angles can reduce the risk of rupture owing to the prevention of localised stress formation in materials. [ABSTRACT FROM AUTHOR]