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Fundamental understanding of removal of liquid thin film trapped between fibers in the paper drying process: A microscopic approach, TAPPI Journal May 2020
ABSTRACT: In the fabrication of paper, a slurry with cellulose fibers and other matter is drained, pressed, and dried. The latter step requires considerable energy consumption. In the structure of wet paper, there are two different types of water: free water and bound water. Free water can be removed most effectively. However, removing bound water consumes a large portion of energy during the process. The focus of this paper is on the intermediate stage of the drying process, from free water toward bound water where the remaining free water is present on the surfaces of the fibers in the form of a liquid film. For simplicity, the drying process considered in this study corresponds to pure convective drying through the paper sheet. The physics of removing a thin liquid film trapped between fibers in the paper drying process is explored. The film is assumed to be incompressible, viscous, and subject to evaporation, thermocapillarity, and surface tension. By using a volume of fluid (VOF) model, the effect of the previously mentioned parameters on drying behavior of the thin film is investigated.
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Pigmented aqueous barrier coatings, TAPPI Journal November 2020
ABSTRACT: The desire for more sustainable packaging has led to the development of new packaging materials that are fiber based. Aqueous coatings are a pathway to improve the recyclability of these materials. Pigments used in these coatings can improve the performance of the coating and reduce cost while further improving the recyclability. Mineral pigments are also considered to be compost neutral. In this paper, we provide the reader a better fundamental understanding of the mechanisms by which pigments work in barrier coatings. A pigment’s mineralogy and physical characteristics are important to how it will perform, and there have been recent pigment developments that improve coating performance. This paper shows that some pigments are better than others in particular barrier applications. Also, pigmented base or pre-coats can be used to prepare the surface for more highly functional coatings that go on top, improving the barrier function of packaging material and reducing overall cost. Finally, the converting operation is of major importance in driving formulation choices for barrier applications.
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Characterization of chia plant (Salvia hispanica) for pulping, TAPPI Journal October 2020
ABSTRACT: In this paper, chia plant was characterized in terms of chemical, morphological, and anatomical properties. Chia plant was characterized with low a-cellulose (30.5%); moderate lignin (23.2%) with syringyl to guaiacyl ratio of 1.41; and shorter fiber length (0.67 mm) with thinner cell wall (1.91 µm) and good flexibility coefficient (71.44). Anatomical features showed that chia plant consists of vessels, fibers, parenchyma cells, and collenchyma cells. Chia plant pulping was evaluated in soda-anthraquinone (soda-AQ) and formic acid/peroxyformic acid (FA/PFA) processes. Chia plant was difficult to delignify in the alkaline process. The FA/PFA process produced higher pulp yield at the same kappa number than the soda-AQ process. Unbleached soda-AQ chia pulp exhibited good properties in terms of tensile, bursting, and tearing strengths, even at the unrefined stage, due to high drainability of the pulps. Alkaline peroxide bleached FA/PFA pulp exhibited better papermaking properties and 2% higher brightness than the D0(EP)D1 bleached soda-AQ pulp.
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Editorial: The next phase of research in academia and industry, TAPPI Journal September 2023
ABSTRACT: The pulp, paper, and textile sectors have contrib-uted to lifestyle improvements for people with the development and commercialization of products like toilet tissue, facial wipes, diapers, and feminine hygiene products, to name a few. Research and development (R&D) efforts in these sectors are critical now more than ever due to the need for healthcare and lifesaving products, as became evident with the COVID-19 pandemic. Additionally, the need to meet net-zero carbon goals and the necessity to revive manufacturing in devel-oped economies clearly emphasize the requirement to ex-amine the R&D landscape. Academia, industry, and governments have respective roles to play in this field.
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Calender barring review with experiences, TAPPI Journal July 2022
ABSTRACT: Excessive calender vibration affects all styles of calender stacks from single to multi-nip, all hard rolls, or a combination of hard and soft rolls. Calender vibration can be forced vibration or self-excited vibration. Forced vibration occurs at the first few harmonics of the calender roll rotational speeds and is caused by imbalance, misalignment, eccentricity, etc. Self-excited vibration, the focus of this paper, occurs at higher frequencies. Feedback paths for self-excited vibration must be understood in order to ameliorate the problem. This is presented in the context of the historical development of the theory of self-excited feedback mechanisms, followed by a survey of self-excited feedback mechanisms in various types of calender stacks. Methodology to determine which feed-back path is present and techniques to control or eliminate the resulting vibration follow. To obtain a flavor of the types of problems faced and practical remedial actions, a variety of experiences with barring issues are provided.
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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.
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Effectiveness of masks in the suppression of COVID-19 cases during the ongoing pandemic in India, TAPPI Journal October 2022
ABSTRACT: Perhaps the worst predicament faced by humanity in the twenty-first century is the COVID-19 pandemic, which is caused by the SARS-CoV-2 virus. Most parts of the world, including India, went into lockdowns for some period because of the massive increase in cases throughout 2020. Face masks became an important counter-measure for protecting the populace, health professionals, and medics, particularly during the period prior to the mass availability of vaccines. This study intends to evaluate the effectiveness of face masks in limiting the spread of the virus. The data for the number of COVID-19 cases was analyzed from January 1, 2022 to May 31, 2022, using Python programming. This timeframe involved face mask mandates and no mask requirement, and hence was considered to be ideal for analyzing the usefulness of face masks. A decline in cases during the mandate was observed, while the opposite occurred without the mandate. The outcome of the research showed that face masks are effective additional measures against the spread of SARS-CoV-2. This study elevates the value of personal protective equipment (PPE), such as face masks, made with nonwovens and other fabrics, as lifesavers in the case of airborne diseases such as COVID-19 and other pulmonary disorders.
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Utilization of palm fiber as papermaking materials: Microscopic structure and chemical pulping, TAPPI Journal October 2022
ABSTRACT: The microscopic structure and pulping properties of palm fiber were explored. Soda cooking and sulfate cooking were conducted and compared in terms of physical strength of the obtained pulps. Sulfate pulp showed better performance than soda pulp, as indicated by the 23% higher tensile index, 49% higher tear index, and 36% higher burst index. To further elevate physical strength, long fibered pulp (LFP), namely commercial softwood sulfate pulp, was mixed with sulfate pulp of palm fiber at levels from 20% to 50%. At the blend level of 50%, tensile index of 52.13 Nœm/g, tear index of 15.63 mNœm2/g, and burst index of 3.42 kPaœm2/g were attained. The lignin in spent liquor from pulping was isolated and characterized. Soda lignin of palm fiber was mainly composed of guaiacyl and syringyl units, and showed weight-average molecular weight of 3616 g/mol.
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Research on improving the basis weight measurement accuracy of tissue paper based on PSO-BP neural network, TAPPI Journal October 2022
ABSTRACT: The near-infrared (NIR) sensor can be used for measuring the basis weight and moisture of tissue paper, but the measurement accuracy is not ideal for this paper grade. The weight range of the tissue is 10~30 g/m2, indicating that it is a low gram weight paper. The temperature and humidity of the production environment significantly impact an NIR sensor. This paper focuses on improving the measurement accuracy of tissue paper basis weight. In order to reduce the influences of temperature and humidity, a mathematical model based on a particle swarm optimization back propagation (PSO-BP) neural network is proposed. In comparison with multiple linear regression measurement models, the basis weight measurement error with the PSO-BP model is within ± 0.5 g/m2. This model can effectively improve the measurement accuracy and has a good effect on overcoming the basis weight nonlinear effect caused by the changes in ambient temperature and humidity.
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Nanocellulose•cationic starch• colloidal silica systems for papermaking: Effects on process and paper properties, TAPPI Journal October 2022
ABSTRACT: Laboratory tests were conducted to better understand effects on the papermaking process and handsheets when recycled copy paper furnish was treated with combinations of nanofibrillated cellulose (NFC), cationic starch, colloidal silica, and cationic retention aid (cPAM; cationic polyacrylamide). Dosage-response experiments helped to define conditions leading to favorable processing outcomes, including dewatering rates and the efficiency of fine-particle retention during papermaking. Effects were found to depend on the addition amounts of cationic starch and colloidal silica added to the system. It was shown that the presence of a polymer additive such as cationic starch was essential in order to achieve large strength gains with simultaneous usage of NFC.