The production of natural greaseproof paper is a highly energy extensive process typically involving intense refining of softwood pulp in order to yield a low porosity, high density sheet, with low air permeance. This study evaluates the addition of Eucalyptus globulus hardwood fibers to the softwood stock as an approach for reducing the specific refining energy needed on both machine-made, and laboratory-made papers. This addition reduced the average fiber dimensions, leading to a net saving of up to 160 kWh per ton produced paper within the refining, while either maintaining or improving the pulp and paper properties.

A novel cellulose nano material was prepared through a controlled Fenton oxidation process utilizing hydrogen peroxide and ferrous ions. The reaction parameters enabled ferrous-catalyzed oxidation, which combined with mechanical treatment resulted in an effective fibrillation of cellulose fibers. Optical microscopy images provided a visual comparison of fiber morphology between untreated hardwood pulp and Fenton-treated samples, clearly illustrating the fibrillation effect. The samples were evaluated for fiber drainage behavior, and conclusions about accessibility and the extent of fibrillation were made. Measurements of the surface charge of the samples revealed an increase in negative charges originating from added carboxyl groups, which is essential for the dispersing and stabilization of cellulose nano fibrils and micro-fibrillated cellulose (CNF/MFC). Fourier-transform infrared spectroscopy (FTIR) confirmed the introduction of the carboxyl groups due to the Fenton treatment. The CNF/MFC material was used as paper coatings, without adding additional materials. The coated samples underwent analyses of permeability and roughness, revealing possibilities for enhancements in barrier properties and hydrophobicity. The results emphasize the ability of Fenton oxidation in generating high-quality small scale cellulosic materials with customized functionalities, underscoring their potential application in advanced coating technologies and sustainable material innovation.

In the past decades, substantial research efforts have been directed towards increasing the availability of renewable and recycled raw materials. Lignin, one of the most abundant natural polymers, constitutes a vast, renewable, and largely untapped source of aromatic structures. In addition, it is one of the most abundant renewable sources of carbon. Despite the countless research projects aimed at valorizing kraft lignin, the largest source of industrial lignin, relatively few commercial kraft lignin products have emerged. Simultaneously, lignosulfonates represent a commercially successful range of products with a steady and growing global market. This paper reviews the current outlook of technical lignin research, including common misunderstandings, and discusses various factors that have hampered the use of lignin as a renewable source of materials and chemicals.

Through Air Drying (TAD) technology enhances high-quality tissue-grade paper production by shaping a wet paper web on a structured fabric using vacuum or molding boxes, followed by hot air displacement drying over TAD cylinders. This study uses CFD modeling with COMSOL Multiphysics to understand drying rate during the molding process better. Two-dimensional models of paper sheets estimated solid content over vacuum time. Tissue samples were generated using COMSOL's interface with MATLAB, enabling a random fiber distribution. Fluid flow and moisture transport were simulated by coupling the Navier-Stokes and advection-diffusion equations, while Darcy's law with inertial correction described fluid migration within fibers, considering equilibrium between moist air and liquid water. Simulations examined the impact of refining levels and fiber compositions for basis weights from 15 to 30 g/m2. Material properties, including porosity and permeability, were calibrated with laboratory tests and validated in pilot experiments. Results showed that increased refining of softwood pulp significantly affects porosity and initial dryness, achieving reasonable agreement between predicted and actual tissue dryness. The calibrated models could be a first step to improve energy efficiency in TAD processes, paving the way for more sustainable tissue-making methods.

Unplanned pump failures in asset-intensive industries like pulp and paper lead to significant production losses. Data-driven predictive maintenance through anomaly detection has recently appeared to be useful in industrial settings. However, this approach is hampered by the infeasibility of manually annotating multivariate sensor data for supervised learning. While unsupervised anomaly detection offers a promising approach, a key challenge is the lack of structured ground-truth labels for evaluation derived from sparse, unstructured maintenance logs. This paper addresses this gap by introducing a fully unsupervised framework that systematically transforms window-level sensor data for model training and utilizes maintenance notifications to enable robust model evaluation. We implement this approach on a critical process pump in a paperboard mill on an industrial scale, with data that extends for a year. The framework contains a reproducible log-to-label pipeline that generates anomalous and normal time-series windows from industrial sensor and maintenance data. The framework also implements a comprehensive feature engineering process that extracts statistical, spectral, and temporal features from high-frequency sensor readings. We have implemented the framework for a comparative evaluation of five unsupervised anomaly detectors. Our experiments show the usefulness of the framework in practice, and also discuss the tradeoffs, including a critical tradeoff between detection accuracy and deployment feasibility. This work provides a practical framework for evaluating and deploying unsupervised anomaly detection models in real-world industrial settings where labeled data is almost unavailable.

Strongly attractive forces act between superhydrophobic surfaces across water due to the formation of a bridging gas capillary. Upon separation, the attraction can range up to tens of micrometers as the gas capillary grows, while gas molecules accumulate in the capillary. We argue that most of these molecules come from the pre-existing gaseous layer found at and within the superhydrophobic coating. In this study, we investigate how the capillary size and the resulting capillary forces are affected by the thickness of the gaseous layer. To this end, we prepared superhydrophobic coatings with different thicknesses by utilizing different numbers of coating cycles of a liquid flame spraying technique. Laser scanning confocal microscopy confirmed an increase in gas layer thickness with an increasing number of coating cycles. Force measurements between such coatings and a hydrophobic colloidal probe revealed attractive forces caused by bridging gas capillaries, and both the capillary size and the range of attraction increased with increasing thickness of the pre-existing gas layer. Hence, our data suggest that the amount of available gas at and in the superhydrophobic coating determines the force range and capillary growth.

This study investigates the preparation and characterization of cellulose nanofibrils (CNF) derived from hardwood bleached kraft pulp (HWBK) through an oxidation and homogenization process. The HWBK was treated according to a Fenton process using ferrous sulfate (FeSO₄·7H₂O) to enable Fe²⁺ ions to adsorb and diffuse into the pulp fibers. Subsequently, hydrogen peroxide (H₂O₂) was introduced to initiate an oxidation reaction catalyzed by the embedded Fe²⁺ ions, facilitating the breakdown of the fiber structure. The oxidized fibers were then thoroughly washed and subjected to PFI mill refining to produce a uniform CNF dispersion. The properties of the CNF dispersion, including its viscosity, were assessed to determine the extent of nanofibrillation. Characterization techniques such as polarized optical microscopy and charge density test were employed to analyze the morphological and chemical features of the resulting CNF. The findings demonstrate a successful preparation of CNF from HWBK, with potential applications in various nanocomposite and biodegradable materials. The project is still ongoing and other characteristic test such as energy-dispersive X-ray spectroscopy (EDS) and AFM are in the target. Results will be discussed in relation to other CNFs, especially those using Fenton chemistry.

We report on practical experiences concerning supervising industry PhD projects. An industry PhD project is especially interesting because of the added complexity (Borell-Damian et al., 2010). Within this frame, we define an industry PhD project to be a training setting at the graduate level that finally leads to a doctoral thesis, including as well a substantial industry presence in the background and during the project. The candidate can either be an industry employee performing a PhD project under academic supervision from the university side, or a university employee with direct or in-kind industry financing, or simply an academic working on a PhD project with a topic inspired by direct collaborations with the industry.We have been engaged ourselves in several such projects and hold expertise in supervising ‘pure’ academic PhD projects. In our view, both supervision situations are challenging (Lee, 2008) and have specific and interesting features, as well as rewarding ones (Knowledge Foundation, 2024) that are here of interest.Looking from the supervisor perspective, we pose three main questions: (1) What are the benefits of being a supervisor enrolled in an industry PhD project? (2) What are the typical involved drawbacks? (3) What impact are you expecting as a result of your supervision work in a project where the industry company plays an important role? To address these questions, we rely on our own experiences as PhD supervisors and on the feedback collected from a large number of other supervisors. This feedback is analyzed statistically using data assimilated via questionnaires.

Acknowledgements are due to former and present colleagues for fruitful discussions and for their participation in a survey. The presented work is part of the Pro2BE academic environment and Maths@KAU at Karlstad University, Sweden.

References:Borell-Damian, L. et al. (2010), Collaborative Doctoral Education: University-Industry Partnerships for Enhancing Knowledge Exchange Higher Education Policy, 23, 493–514.Lee, A. (2008) How are doctoral students supervised? Concepts of doctoral research supervision, Studies in Higher Education, 33:3, 267-281, DOI: 10.1080/03075070802049202.The Knowledge Foundation (2024), Utvärdering av Företagsforskarskolor (in Swedish), ISBN 978-91-527- 8335-1, https://www.kks.se/app/uploads/2024/03/Foretagsforskarskolorutvardering-2024.pd

Research and applications of superhydrophobicity and superamphiphobicity has increased ever since Wenzel and Cassie-Baxter wetting types were presented and especially since the water superrepellency of the lotus leaf was observed. Applications are exemplified (1) but also potential drawbacks in their usage (2). Basic understanding of the non-wetting mechanisms comes from theoretical work (3, 4) and from surface force measurements, using either droplets or particle probes (5,6). We report surface force (AFM colloidal probe microscopy) measurements combined with confocal laser microscopy imaging (CLSM) (7-9) allowing long-range capillary forces to be measured at the same time as the growing gaseous capillary is imaged. The different contributions to Gibbs free energy of capillary formation from the works of surface tension-area and pressure-volume were discerned, as well as a remaining term for the three-phase contact line (TPCL) contributions (pinning, depinning and line energy). We discuss a remaining challenge to more correctly determine the TPCL contributions, e.g. the line path (10). Superhydrophobicity and superamphiphobicity is most often described as a surface having a liquid contact angle of above 150° and a low roll-off contact angle. Studies suggest that there are several phenomena occurring with a transition from force curves of constant pressure or volume to those showing both non-constant pressure and volume of the gas capillary. This wetting transition can be used to define the super liquid-repellency from a surface forces point of view.

Acknowledgements to colleagues at Max Planck institute in Mainz, Omya Development AG, Tampere

University and RISE; to SSF Swedish Foundation for Strategic Research and Pro2BE academic environment at Karlstad University.

References

1. Wang et al. Nature 2020, 582 (7810), 55-2. Erbil. Langmuir 2020, 36 (10), 2493-3. Erbil. Colloids and Interfaces 2021, 5 (1), 84. Shardt et al. Langmuir 2018, 34 (40), 12191-5. Eriksson&Swerin. Current Opinion in Colloid & Interface Science 2020, 47, 46-6. Thormann. Current Opinion in Colloid & Interface Science 2017, 27, 18-7. Eriksson et al. Scientific Reports 2023, 13 (1), 67948. Eriksson et al. Langmuir 2024, 40 (9), 4801-9. Eriksson et al. ACS Nano 2019, 13 (2), 2246-10. Dorrer&Rühe. Langmuir 2007, 23 (6), 3179-

Factors affecting the swelling of cellulosic fibers are considered in this review.  Emphasis is placed on aqueous systems and papermaking fibers, but the review also considers cellulose solvent systems, nanocellulose research, and the behavior of cellulosic hydrogels.  The topic of swelling of cellulosic fibers ranges from effects of humid air, continuing through water immersion, and extends to hydrogels and the dissolution of cellulose, as well as some of its derivatives.  The degree of swelling of cellulose fibers can be understood as involving a balance between forces of expansion (especially osmotic pressure) vs. various restraining forces, some of which involve the detailed structure of layers within the fibril structure of the fibers.  The review also considers hornification and its effects related to swelling. The expansive forces are highly dependent on ionizable groups, pH, and the ionic strength of solution.  The restraining forces depend on the nature of lignin, cellulose, and their detailed structural arrangements.