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Probing the molecular weights of sweetgum and pine kraft lignin fractions, TAPPI Journal June 2021
ABSTRACT: The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physico-chemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30•150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to determine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weight-lignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.
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Quantification of vegetable oil in recycled paper, TAPPI JOURNAL September 2020
ABSTRACT: Vegetable soybean oil is commonly used in cooking foods that are packaged in takeaway paper-board containers. Vegetable oil is hydrophobic, and in sufficiently high concentration, could interfere with interfiber bonding and result in paper strength loss. In order to quantify the effect of oil on the resulting paperboard strength, it is necessary to quantify the oil content in paper. A lab method was evaluated to determine the soybean oil content in paper. Handsheets were made with pulps previously treated with different proportions of vegetable oil. Pyrolysis gas chromatography-mass spectrometry (pyGCMS) was used to quantify the amount of oil left in the handsheets. The results revealed a strong correlation between the amount of oil applied to the initial pulp and the amount of oil left in the handsheets.In addition, the effect of vegetable oils on paper strength may be affected by the cooking process. Vegetable oil is known to degrade over time in the presence of oxygen, light, and temperature. The vegetable oil was put in an oven to imitate the oil lifecycle during a typical pizza cooking process. The cooked oil was then left at room temperature and not protected from air (oxygen) or from normal daylight. The heated, then cooled, oil was stored over a period of 13 weeks. During this time, samples of the aged oil were tested as part of a time-based degradation study of the cooked and cooled oil.
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Editorial: New coating grades require new tests: Barrier performance inside the package, TAPPI Journal November 2024
The TAPPI Journal special Coating issue is an annual issue that focuses on paper coating and coated papers. It is drawn from presentations at TAPPICon and from other submissions on the topic of paper coating. The TAPPICon 2024 Coating track was rich in high-quality technical content. In fact, the papers were of such significance that Coating members of the TAPPI Journal Editorial Board, which include me, Gregg Reed, and Gregory Welsch, decided that a second paper coating-related special issue would be appropriate for the TAPPI Journal editorial calendar. In addition to the current issue on Barrier Coating Testing, there will be another issue on Coating Fundamentals in early 2025.
Journal articles
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Test method and coating composition impact on measured moisture vapor transmission rate for waterborne coatings on paper, TAPPI Journal November 2024
ABSTRACT: Moisture vapor barrier is one of the necessary performance attributes for paper packages. Two methods are typically employed to assess the moisture vapor transmission rate (MVTR): the gravimetric cup method (ASTM E96) and the MOCON method (ASTM F1249). While those tests have been compared for free standing polymeric films, less is understood about their application in coated paper. Our results show that, despite a general agreement between the two methods, discrepancies exist where test protocols and material properties of coated paper impact the MVTR measurement. The measurement discrepancies can be explained by differences in local moisture concentration. Our study provides new insights on moisture vapor barrier assessment of waterborne coatings on paper and implications for achieving paper packages with improved barrier performance.
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Evaluation of folding effects on coating damage, TAPPI Journal November 2024
ABSTRACT: Barrier coatings on paperboard need to maintain integrity during converting and end-use for effective barrier performance. Folding is one of the most common deformations during converting; however, factors that affect damage during folding are not well defined. This is partly because methods to fold specimens and characterize damage are not standardized and the results are generally not transferable. In this work, we describe a method to fold paper specimens precisely and reproducibly. The keys to folding include using a defined geometry and controlled deformation. Multiple methods can be used to quantify damage; in this case, we use differences in permeability as a measure of how the coating becomes more open. Damage is sensitive to the degree of compression after the initial folding. Using a shim for support provides a defined amount of compression and minimizes the sensitivity to the applied pressure.
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Critical parameters for tall oil separation I: The importance of ration of fatty acids to rosin acids, TAPPI Journal September 2019
ABSTRACT: Tall oil is a valuable byproduct in chemical pulping of wood, and its fractions have a large spectrum of applications as chemical precursors, detergents, and fuel. High recovery of tall oil is important for the economic and environmental profile of chemical pulp mills. The purpose of this study was to investigate critical parameters of tall oil separation from black liquor. To investigate this in a controlled way, we developed a model test system using a “synthetic” black liquor (active cooking chemicals OH- and HS- ions), a complete process for soap skimming, and determination of recovered tall oil based on solvent extraction and colorimetric analysis, with good reproducibility. We used the developed system to study the effect of the ratio of fatty acids to rosin acids on tall oil separation. When high amounts of rosin acids were present, tall oil recovery was low, while high content of fatty acids above 60% significantly promoted tall oil separation. Therefore, manipulating the content of fatty acids in black liquor before the soap skimming step can significantly affect the tall oil solubility, and hence its separation. The findings open up chemical ways to improve the tall oil yield.
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A new technique for the measurement of show-through mottle of fine paper, TAPPI Journal September 2019
ABSTRACT: Mottling within print-through and show-through is caused by the variability of the local optical properties of the sheet. This mottling is visually disturbing and a mark of poor paper quality. The ability to predict print-through mottle of printed paper by measuring show-through mottle on the unprinted sheet would be a valuable asset for paper machine control.We examined the relationship between print-through mottle and show-through mottle. We worked with nine samples of 60 lb. uncoated fine paper (90 g/m2), from various North American paper companies, that were printed on an offset press, 400K (400% Black), on both sides. A show-through mottle instrumental determination technique was developed using an existing Fast Fourier Transform-based algorithm. The nine samples examined were ranked similarly by the visual evaluation of print-through mottle and by the instrumental determination of show-through mottle. We thus established that show-through on the unprinted sheet can be used as a reliable predictor of print-through, therefore saving time and money for papermakers. We also found a significant two-sidedness in show-through for some of the samples.
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Three-dimensional pore structure visualization and character
Three-dimensional pore structure visualization and characterization of paper using X-ray computed tomography, TAPPI JOURNAL September 2017
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On the nominal transverse shear strai to characterize the severity of creasing, TAPPI JOURNAL April 2018
On the nominal transverse shear strai to characterize the severity of creasing, TAPPI JOURNAL April 2018
Journal articles
Magazine articles
Effect of conductivity on paper and board machine performanc
Effect of conductivity on paper and board machine performance— a review and new experiences, TAPPI JOURNAL October 2017