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Journal articles
Pre-damping effects on water absorption and drying dynamics in flexographic printing, TAPPI Journal November 2025
ABSTRACT: Optimizing flexographic printability can involve the ink and the substrate, as well as the printing process. It has been widely reported in the literature that controlling topography of the substrate and its porosity are vital for good flexographic printability, especially when using water-based inks. This study focuses on how pre-damping a surface impacts liquid absorption and improves wet trapping (ink on ink with no intermediate drying) in flexographic printing. A Prüfbau universal print tester was adapted to analyze flexographic wet-on-wet ink printing and trapping using yellow and magenta inks for contrast. Slow drying of the first ink layer (yellow) leads to mottle when the second layer (magenta) is applied. The study explores the “wet sponge” hypothesis: a pre-damped surface should absorb liquid faster. The Lucas- Washburn equation describes long-term absorption, but it does not capture short-term uptake, which instead follows a linear dependence on time.
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
Editorial: Advancing the Digital Twin paradigm — From network mechanics to functional paper physics, TAPPI Journal March 2026
This Special Paper Physics Issue of TAPPI Journal serves as a critical bridge between the phenomenological observations shared at the last International Paper Physics Conference in Wuppertal, Germany, and the rigorous quantification required to realize the “Digital Twin” paradigm. This paradigm involves the creation of a virtual dynamic representation of a process that acts as a real-time counterpart of the actual one. We are particularly indebted to Jaan-Willem Simon of the University of Wuppertal, whose leadership was pivotal in translating the conference’s academic rigor into this scholarly collection.
Journal articles
Estimating dose and interaction of X-rays with cellulose-based fibrous materials using micro-computed tomography, TAPPI Journal March 2026
ABSTRACT: Micro-computed tomography (ìCT) has a reputation as a nondestructive analysis method. Unfortunately, this leads to the common misconception that radiation damage of the sample does not play a role. With the increased use of ìCT in laboratory-based machines, more and more cellulose-based materials are studied. In this paper, we show with three examples that radiation damage is important in dry and wet paper and in viscose fibers. In an attempt to quantify radiation damage, we came up with a workflow that enables researchers to predict the X-ray dose within a laboratory-based ìCT machine. This gives researchers the possibility to quantitatively judge the influence of radiation damage on each measured sample. While one cannot extend the measured doses from one machine to another, one can still apply the work flow presented in this study to any ìCT setup. In this way, it is possible to minimize radiation damage by choosing the best parameters in a ìCT for obtaining perfect data with no or little radiation damage.
Journal articles
Point load measurements on paperboard packages and bulging, TAPPI Journal March 2026
ABSTRACT: Paperboard packaging is made by processing board materials into sheets or rolls and shaping them through creasing, cutting, folding, and erecting. The conversion process generates residual moments at the folds that cause panel bulging. This study experimentally investigates how the bulging introduced during the converting processes influence the mechanical response of paperboard packages during point load testing within the elastic deformation range. The study shows that panel bulging may significantly affect packaging performance as-perceived strength and stiffness. Bulging, influenced by the board’s basis weight, can affect the package performance even more than packaging stiffness. Point load tests in the elastic region were performed on empty packages (78 mm × 50 mm × 110 mm) with force applied at specific points along their long sides. The packages evaluated in this study were made of two identically processed materials of different grammages. The heavier material showed more pronounced bulging than the lighter one, leading to overlapping force-displacement curves for the packages, and to that, a lower force and stiffness may be measured at a certain indentation depth for the package of heavier material. This complicates material choice according to functional requirements. The results show that a highly bulged package might resemble one with less bulging of another material. According to the results, it is not certain that a higher grammage package shows a higher indentation force and stiffness than a lower grammage package when measured at a certain indentation. This indicates that optimizing the creasing and folding processes can be a way to enhance performance rather than simply increasing board weight. The study underscores the importance of controlling converting parameters, especially creasing and folding behavior. Well-performed creasing and folding gives a low residual momentum, little bulging, and a high stiffness and compression strength at point loading in the elastic region. Proper optimization can improve packaging performance and manual handling user-friendliness.
Journal articles
AOX Content of Paper Manufactured with 'Chlorine Free' Pulps
AOX Content of Paper Manufactured with 'Chlorine Free' Pulps, 1995 Papermakers Conference Proceedings
Journal articles
Monitoring mechanical seal performance to reduce fixed costs
Monitoring mechanical seal performance to reduce fixed costs, Solutions! Online Exclusives, June 2003