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Understanding wet tear strength at varying moisture content in handsheets, TAPPI Journal January 2021
ABSTRACT: A laboratory study was conducted looking at the effects of moisture content on wet tear strength in handsheets. Three different wetting techniques were used to generate the wet tear (Elmendorf-type) data at varying moisture levels, from TAPPI standard conditions (dry) to over 60% moisture content (saturated). Unbleached hardwood and softwood fiber from full-scale kraft pulp production were used. The softwood fiber was refined using a Valley beater to reduce freeness. Handsheets were made with a blend of hardwood and softwood and with refined softwood, without the addition of wet-end chemistry. The resulting grams-force tear data obtained from the test was indexed with basis weight and plotted versus both moisture content and dryness. As moisture content levels in the handsheets increased, the wet tear strength also increased, reaching a critical maximum point. This marked a transition point on the graph where, beyond a critical moisture content level, the tear strength began to decline linearly as moisture increased. This pattern was repeated in handsheets made from a blend of hardwood and softwood and from 100% refined softwood.
Journal articles
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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.
Journal articles
Magazine articles
Guest Editorial: Coating research addresses new product demands in response to global pandemic, TAPPI Journal November 2020
ABSTRACT: For all of us, the year 2020 has been one of significant challenge. Our communities, companies, institutions, organizations, and families have had to make many tough decisions and change our way of life as a result of the global pandemic.
Journal articles
Preparation of a vegan leather from mycelium with papermaking method, TAPPI Journal June 2026
ABSTRACT: With growing concern over the environmental impacts of both natural leather and conventional synthetic leathers, the development of sustainable and eco-friendly leather alternatives has become an urgent research priority. In this study, an innovative wet papermaking strategy is proposed to fabricate continuous, homogeneous mycelial sheets from chitin-rich fungal mycelium, mimicking the matrix structure of genuine leather. These mycelial sheets were chemically modified to meet the performance requirements of leather foam layers. Subsequently, the modified mycelial sheets were combined with a substrate fabric to produce a novel mycelium-based leather composite (myco-paper leather) that achieves an excellent balance of mechanical properties and tactile qualities. Experimental results demonstrate that the mycelium-sheet-based leather substitute exhibits remarkable mechanical performance, with a tensile strength of approximately 45 MPa and an elongation at break of about 10.5%. After lamination with the substrate fabric, the composite material shows a tear strength of approximately 16 N, along with a desirable hand feel and surface texture. Following tannic acid tanning, the mycelial sheets also exhibit significant antimicrobial and antifungal properties, forming an inhibition zone of approximately 2 mm against Staphylococcus aureus. Through reinforcement with plant fibers, the developed material attains both strength and flexibility, indicating that the wet papermaking of mycelial sheets is a feasible and scalable approach for producing sustainable leather alternatives. This work not only employs a simple and mature papermaking process to process fungal mycelium but also provides a new conceptual and practical foundation for the large-scale production of bio-based leather substitutes. The findings have significant implications for advancing a low-carbon, sustainable leather industry.
Journal articles
Water and grease resistance of paperboard coated with long chain cellulose fatty acid esters using electrostatic powder coating, TAPPI Journal April 2026
ABSTRACT: Fiber-based materials used for foodservice, takeaway, and other packaging applications must typically provide water and grease resistance. Simultaneously, there is growing interest towards bio-based and renewable barrier coatings. In this study we applied thermoplastic long chain fatty acid cellulose esters onto paperboard using electrostatic powder coating to create barrier properties of interest. Electrostatic powder coating provides a water-free process to tackle moisture-induced quality issues and to provide an even coating layer. Cellulose octanoate and palmitate esters were produced in pilot scale. These were ground into fine particles using liquid nitrogen and applied onto paperboard sheets using an electrostatic powder gun. The loosely packed coatings were fixed and fused onto the paperboard by hot pressing. We characterized the coated sheets for coating thickness, contact angles with water, water absorption, grease resistance (KIT), and olive oil barrier. Two commercial polyethylene powders were used as references. Our results indicated that the long chain cellulose fatty acid ester coatings were thermoplastic and hydrophobic with contact angles above 100°. Water absorption was similar to the reference coatings. While grease resistance was lower than with the references, the cellulose ester coatings slowed down diffusion of olive oil through the paperboard. Cellulose octanoate ester with a lower melt viscosity already provided smooth coatings after the initial hot pressing step, while in most cases, the second post hot pressing step further improved the barrier properties.
Journal articles
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Study on the effect of aluminum diethyl phosphinate in synergy with ammonium polyphosphate on the flame retardancy of cellulose paper, TAPPI Journal April 2025
ABSTRACT: This paper involved the synergistic incorporation of ammonium polyphosphate (APP) and diethyl aluminum phosphinate (AlPi) as flame-retardant fillers for producing flame-retardant paper. The research revealed that APPs were square particles with a smooth surface, and their solubility was 0.29 g/100 mL at 20°C, which increased to 4.12 g/100 mL at 60°C. The surfaces of AlPis were rough and irregular. The solubility of AlPi was 0.023 g/100 mL at 20°C, and the solubility remained stable when the temperature increased. The addition of AlPi had a minor influence on the pulp beating degree. The tensile strength of kraft/APP/AlPi decreased with the increase of the AlPi addition. For a paper with 20 wt% APP and 0 wt% AlPi, the limiting oxygen index (LOI) value was 27.2%, and it burned completely at the eighth second during vertical combustion. When the AlPi additive content increased to 20 wt%, its LOI value increased to 32.2%, and the vertical combustion self-extinguished as soon as the flame was removed. Scanning electron microscopy (SEM) showed that the char residue of the kraft/APP/AlPi had a more complete fiber network structure than that of kraft/APP. The Raman spectroscopy indicated that the area ratio of the D (amorphous phase; disordered graphite vibration) band to the G (crystal phase; graphite carbon vibration) band (ID/ IG) ratio of kraft/APP/AlPi was lower than that of kraft/APP, meaning that the graphitization degree of the char residue of kraft/APP/AlPi was higher than that of kraft/APP, which indicated the kraft/APP/AlPi had better flame retardancy.
Journal articles
Magazine articles
Non-process elements in the recovery cycle of six Finnish kraft pulp mills, TAPPI Journal March 2023
ABSTRACT: In this work, the aim was to study the distribution and accumulation of the non-process elements (NPEs) in the recovery cycle of Finnish pulp mills and look at whether the geographical location (North vs. South) correlates with the current Finnish NPE levels. In addition, a comparison to older similar Finnish measurements was made with an attempt to analyze the reasons behind differences in the most typical non-process elements, aluminum (Al), silicon (Si), calcium (Ca), phosphorus (P), magnesium (Mg), manganese (Mn), chlorine (Cl), and potassium (K), taking into account the main elements in the white liquor, sodium (Na) and sulfur (S). The extensive laboratory results gained in this study are from seven sampling points at six pulp mills and present analytical data of metal concentrations. The data obtained presents an update to previous NPE studies. The levels found did not statistically differ between North and South Finland. The NPE levels, apart from phosphorus, found in Finnish pulp mills today have not changed considerably compared to the levels in earlier investigations in the 1990s. In the newest data, the phosphorus concentration was consistently higher in the as fired black liquor, electrostatic precipitator (ESP) ash, lime mud, and green liquor than in the previous results. In addition, the levels of Al, Si, Ca, P, and Mg in recovery boiler ESP ash were consistently higher compared to the older results. As the mills start to close their systems more, a stronger accumulation of NPEs can be expected, increasing the likelihood of more operational problems in the process. Further understanding of where the NPEs accumulate and how they can be most effectively removed will be valuable knowledge in the future.
Journal articles
Magazine articles
Recovery boiler back-end heat recovery, TAPPI Journal March 2023
ABSTRACT: Sustainability and efficient use of resources are becoming increasingly important aspects in the operation of all industries. Recently, some biomass-fired boilers have been equipped with increasingly complex condensing back-end heat recovery solutions, sometimes also using heat pumps to upgrade the low-grade heat. In kraft recovery boilers, however, scrubbers are still mainly for gas cleaning, with only simple heat recovery solutions. In this paper, we use process simulation software to study the potential to improve the power generation and energy efficiency by applying condensing back-end heat recovery on a recovery boiler. Different configurations are considered, including heat pumps. Potential streams to serve as heat sinks are considered and evaluated. Lowering the recovery boiler flue gas temperature to approximately 65°C significantly decreases the flue gas losses. The heat can be recovered as hot water, which is used to partially replace low-pressure (LP) steam, making more steam available for the condensing steam turbine portion for increased power generation. The results indicate that in a simple condensing plant, some 1%•4% additional electricity could be generated. In a Nordic mill that provides district heating, even more additional electricity generation, up to 6%, could be achieved. Provided the availability of sufficient low-temperature heat sinks to use the recovered heat, as well as sufficient condensing turbine swallowing capacity to utilize the LP steam, the use of scrubbing and possibly upgrading the heat using heat pumps appears potentially useful.
Journal articles
Magazine articles
Using novel DNA methods to achieve higher process efficiency and performance, TAPPI Journal January 2023
ABSTRACT: Uncontrolled microbiological activity is a challenge for recycled fiber (RCF) mills as it can have negative effects on production and end-product quality. The microbes that exist in these systems have been largely unknown, and the strategies employed to control microbiology have been non-specific. Understanding the specific microbial groups present in RCF mills, their properties, and where they exist, as well as having the ability to accurately measure the true troublemakers, are key to targeted control of the bad actors. In this study, we present the results of a global survey of over 40 RCF paper machines. The same RCF-specific problem-causing bacterial groups were found on different continents, including large densities of newly identified bacteria in paper processes. Those can degrade cellulose and starch, produce acids and odorous substances, and have a significant impact on fiber strength and additive consumption. We also demonstrate how modern DNA tools can quantify the impact of biocidal countermeasures against the actual troublemakers, including bacteria found to degrade cellulose during RCF pulp storage, which may be linked to a negative impact on end-product strength. These novel DNA tools give producers updated biocide program key performance indicators (KPIs) and actionable information to more effectively design and adjust microbiological control to achieve higher process efficiency and performance.
Journal articles
Magazine articles
Advanced real-time digital microscopy of foaming processes, TAPPI Journal January 2023
ABSTRACT: The properties of aqueous foams play a major role in foam forming and foam coating. Inline real-time foam measurements provide highly desired opportunities for optimization and control of foaming processes. This paper presents inline digital microscopy measurements of aqueous foams in foaming processes. It presents methods for providing detailed information on foam quality parameters, such as foam density and foam homogeneity in real time from the process. In addition, this study evaluates the performance of transillumination and front-light illumination in imaging of foams. The tests show very good results for the transillumination approach. Limitations of the image-based optical technique are discussed, and the precision of bubble size distribution measurement is assessed with a certificated reference substance. The measured foam densities are compared against the reference foam densities in the range 100•300 g/L, providing a linear correlation with R2 value of 0.99. In the case of heterogenous foams with a wide bubble size distribution, the bubble size-dependent dimensionless depth of field must be taken into account to obtain accurate estimates of foam density. Bubble-scale foam homogeneity is described by the standard deviation of bubble size distribution in foam.