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Improving paper wet strength via increased lignin content and hot-pressing temperature, TAPPI JOURNAL October 2020
ABSTRACT: It is known that the strength properties of wood-based paper materials can be enhanced via hot-pressing techniques. Today, there is a desire not only for a change from fossil-based packaging materials to new sustainable bio-based materials, but also for more effective and eco-friendly solutions for improving the dry and wet strength of paper and board. Against this background, hot pressing of paper made from high yield pulp (HYP), rich in lignin, becomes highly interesting. This study investigated the influence of pressing temperature and native lignin content on the properties of paper produced by means of hot pressing. Kraft pulps of varied lignin content (kappa numbers: 25, 50, 80) were produced at pilot scale from the same batch by varying the cooking time. We then studied the effect of lignin content by evaluating the physical properties of Rapid Köthen sheets after hot pressing in the temperature range of 20°C•200°C with a constant nip pressure of 7 MPa. The pilot-scale cooked pulps were compared with reference samples of mill-produced northern bleached soft-wood kraft (NBSK) pulp and mill-produced chemithermomechanical pulp (CTMP).Generally, the results demonstrated that lignin content had a significant effect on both dry and wet tensile index. All of the pilot cooked pulps with increased lignin content had a higher tensile index than the reference NBSK pulp. To obtain high tensile index, both dry and wet, the pressing temperature should be set high, preferably at least 200°C; that is, well above the glass transition temperature (Tg) for lignin. Moreover, the lignin content should prefera-bly also be high. All kraft pulps investigated in this study showed a linear relationship between wet strength and lignin content.
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Crossflow filtration of green liquor for increased pulp production, improved green liquor quality, and energy savings, TAPPI JOURNAL October 2020
ABSTRACT: A new green liquor filtration system has been installed and commissioned at the Ence pulp mill in Pontevedra, Spain. The filtration system is based on microfiltration and was developed in collaboration with the KTH Royal Institute of Technology in Stockholm, Sweden. The patented method for efficient purification of green liquor decreases the non-process element (NPE) content by providing more efficient solids/liquid separation, reducing energy and chemical consumption in pulp mills and increasing production capacity by eliminating certain capacity bottlenecks. The process has been continuously tested at the Aspa Bruk Mill outside Askersund, Sweden, since 2013. The technology has proven to create nearly particulate-free green liquor during the purification process. The technology can also be used to polish white liquor to provide higher pulp quality.To provide for a simple and cost-effective installation, the system was designed as a skid-mounted unit that is pre-piped, instrumented, and tested before shipment. The system is modular and allows for easy expansion of capacity. This paper discusses the process design, process integration, and startup of the new system, along with experiences from the first months of operation.
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Multilayering of conventional latex-based dispersion coatings containing small amounts of silica nanospheres: Runnability on a pilot scale flexographic coater and barrier performance, TAPPI Journal November 2023
ABSTRACT: The addition of functional coatings to packaging materials is a key requirement for increasing their performance and creating innovative packaging solutions. Flexography, a cost-effective printing method commonly used to print information and graphics directly onto a wide variety of packaging substrates, shows good potential for applying functional coatings. In this study, conventional clay-latex coating formulations containing approximately 1.3 wt% silica nanospheres were applied to a linerboard using a pilot scale flexographic printing web press. The performance of multilayered silica nanosphere-based coatings was compared with conventional coatings containing talc and/or wax dispersion in terms of coating grammage, runnability, and barrier performance. Coating grammage increased with an increased number of coating layers and a significant decrease in both the water vapor transmission rate (WVTR) and the direct water uptake of water (Cobb 120 wettability test) was observed for coatings containing silica nanoparticles. In general, the silica nanosphere-based coatings performed better than talc-based coatings. Talc/wax-based coatings had the highest variation in surface roughness due to an uneven distribution and variations of coating layers.
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Z-directional testing of paperboard in combined tensile and compression loading, TAPPI Journal May 2024
ABSTRACT: The out-of-plane properties of paperboard are important in several converting applications such as printing, sealing, creasing, and calendering. A juxtaposed tensile and compression curve in the z direction (ZD) will, however, appear to have a kink or discontinuity at 0 stress. The purpose of the present work is to capture the continuous transition between tension and compression and to increase the understanding of the complex ZD properties of paperboard by cyclic testing. In this attempt to unify the ZD tensile and compressive behavior of paperboard, samples were laminated to the testing platens using heat seal laminate film. The method for adhering the samples was compared to samples that were laminated and glued to the testing platens. The edge effects of the cutting method were evaluated in compression testing with samples not attached to the testing platens. The flat slope seen in the initial part of the pure compression curve disappeared when the samples were laminated to the testing platens. The flat slope was instead replaced by a continuous response in the transition across 0 N. The stiffness in the transition region resembled the response in tensile testing. When the testing is cycled, the material exhibits a history dependence. Starting the cycle in either compression or tensile will show an effect on the stiffness at the transition, as well as the compressive stiffness. However, the ultimate tensile strength is unaffected.
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Utilization of Areca leaf residues for sustainable production of greyboard, TAPPI Journal May 2024
ABSTRACT: This study primarily focused on the production of greyboard using waste materials from small scale industries, and specifically using Areca leaf waste fibers as a sustainable and environmentally friendly resource. Areca leaf waste fibers were employed as the primary raw material for greyboard manufacturing. The resulting greyboard exhibited commendable properties, including a tear index of 7.53 mN·m2/g, tensile index of 18.34·N·m/g (i.e., breaking length of 1870 m), burst factor of 9.24 (gf/cm2)/(g/m2) and stiffness factor of 33.1. This greyboard was created through a series of steps, including hydrothermal treatment of the material at 155°C and mechanical pulping refinement. The produced greyboard met the specifications outlined in the Indian Standard 2617 (1967) for greyboard. The key objective of this work was to leverage agricultural waste resources to develop a chemical-free greyboard, resulting in reduced waste disposal in open fields and a decrease in chemical usage within the greyboard manufacturing industry. Various characterization techniques, including field emission scanning electron microscopy (FE-SEM), attenuated total reflection•Fourier transform infrared (ATR-FTIR) analysis, and X-ray diffraction (XRD), were used to assess the fiber quality, including aspects such as functional groups, morphology, and crystallinity for the materials used in the manufacturing process.
Journal articles
Local delamination in pharmaceutical blister packages • A thermomechanical theory on buckling of heat-sealed composite laminates in flexible packaging, TAPPI Journal July 2025
ABSTRACT: Pharmaceutical blister packages consist of cavities made from a thick polymeric form foil and a thin aluminum lid foil. Heat-sealing technology is usually used to bond the lid foil to the form foil. Occasionally, the sealed area shows buckling defects of the lid foil, which allow contamination to enter into the cavity. A contaminated product is a worst-case scenario for pharmaceutical production and must be avoided. We discuss a thermomechanical theory on buckling defects in blister packages and derive strategies to avoid these. The theory is based on the assumption that the seal of a blister packaging behaves like a laminate of thin composite layers under compressive load. Literature research on buckling of thin laminated films, thermal behavior of polymers, and seal strength of heat-sealed polymers provides the technical and physical background to elaborate the theory. The theory comprises three elements: an initial condition regarding thermal load and precedent defects; a buckling condition; and a crack propagation condition. The plausibility of the theory is verified using model calculations and heat-seal tests. The paper concludes with strategies against buckling of heat-sealed lid foils and an outlook on other applications in laminating and coating of polymer films.
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Edge crush testing methods and box compression modeling, TAPPI Journal August 2022
ABSTRACT: While multiple test procedures have been developed to assess the inherent compressive strength of corrugated materials (edge crush test, ECT), limited work has explored the appropriateness of each in the context of box compression modeling. This study incorporates a variety of real-world samples, highlighting the varying challenges different ECT methods face in measuring the intrinsic compressive resistance of combined corrugated board. We examine each of these methods as inputs for different types of models, as well as discuss the propagation of measurement variation through the modeling effort. By highlighting the cases in which a given ECT method no longer proves to be an optimal parameter in box compression strength modeling, we explore how we might better measure this material property.
Journal articles
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Effects of agitator blade scaling on mixing in dissolving tanks, TAPPI Journal April 2022
ABSTRACT: Hard calcium carbonate scale often forms on the agitators in smelt dissolving tanks. The effects of this scale on mixing are not well understood. While mixing in tanks has often been modeled in the literature, there have been no studies involving agitator scaling. To better understand the impact of agitator scaling on hydrodynamics and tank concentrations, a steady state, three-dimensional (3D) model has been developed for a smelt dissolving tank at a kraft pulp mill. In this work, four cases are compared: an agitator with no scaling, mild scaling, moderate scaling, and extreme scaling. The extreme scaling case is representative of scale buildup on a dissolving tank agitator that was significant enough that the agitator had to be stopped and cleaned. The reduction in the agitator fluid jet velocity is relatively small for the mild and moderate scaling cases, but it becomes more significant for the extreme scaling case, for which the results indicate that the mixing of the smelt with the weak wash is likely poor and that there would thus be a risk of smelt pooling.
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Comparative study of guar gum and its cationic derivatives as pre-flocculating polymers for PCC fillers in papermaking applications, TAPPI Journal April 2022
ABSTRACT: In this work, gums from guar seeds were evaluated as a potential precipitated calcium carbonate (PCC) filler pre-flocculant to induce functional filler in papermaking applications. In recent years, guar has been conidered one of the promising wet-end additives due to its abundance, rich source of hemicellulose content, and bio-degradability. However, application of guar gum in filler pretreatment methods for producing high ash paper has scarcely been reported. In this paper, the flocculating ability of three types of guar gum was established with charge analysis and turbidity (NTU) of the system at 1% and 5% for each gum: native gum (NG) having a degree of substitution (DS) of 0, and cationic gums having a DS value of 0.07 (CL) and 0.15 (CH). It was interesting to observe that even at a 5% dose of G, the charge density of PCC did not deviate much from the initial values. The system carried a weak negativeharge, resulting in an unstable colloidal suspension that led to PCC-PCC particle bridging. On the other hand, the operative mechanism of CL and CH during adsorption and PCC flocculation was predicted to be charge neutralization and electrostatic-patch formation, accompanied by particle bridging. Note that CL, with a maximum 47.5% eduction in residual turbidity of PCC at a 1% dose, was much more efficient in doing so than the other two gums; NG had a 40% maximum reduction in residual turbidity at a 5% dose and CH had a maximum 30% reduction at a 1% ose. Later on, floc formation and structure were correlated with optical and field emission scanning electron microscopy (FE-SEM) images. In the next set of trials, paper properties were determined by varying the different gum dosages from 0.2% to 5% at a constant dose of 20% filler. It is also noteworthy to mention that with 1% CL (low DS) dose, PCC retention increased by 39%, which also enhanced the tensile, tear, burst, and opacity properties by 11%, 19%, 5%, and 4.4%, respectively, without significantly affecting the bulk properties. Further, wide-angle X-ray diffraction (XRD) analysis nd Fourier transform infrared (FTIR) analysis revealed that pre-flocculating PCC with a 1% gum dose did not induce any change in crystalline transformation. Based on observation, it was found that cationic gums with low DS values re a better choice for maximizing the strength of paper while maintaining bulk and high opacity when pre-flocculaion is adopted to increase the filler retention in paper.
Journal articles
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Editorial: Impacts from using recycled pizza boxes in furnish: TAPPI Journal’s runner-up to 2021 Best Research Paper, TAPPI Journal August 2022
ABSTRACT: The runner-up to the 2021 TAPPI Journal Best Research Paper was “Incorporation of post-consumer pizza boxes in the recover Fiber Stream: Impact of grease on finished product quality."