This study investigates the swelling and liquid retention properties of cellulosic pulp from cotton waste, cotton linters and conventional dissolving wood pulp in both neutral (water) and alkaline (sodium hydroxide) conditions in regard to the first phase of the viscose process (mercerization). The swelling of single fibers is investigated by microscopic observation of the diameter increase during immersion in the liquids, which resulted in a logarithmic trend over time. The retention properties are investigated by water and lye retention values, and the latter was coupled to the pressability of mercerized pulp through observation of the trend in press factor with increasing pressing times. The different materials behaved similarly in neutral conditions regarding single fiber swelling and retention properties. Alkaline conditions, on the other hand, resulted in increased swelling and retention properties for all materials compared to neutral conditions, and the cotton-based pulps showed higher single fiber swelling and retention of lye, accompanied by impeded pressability. Thereafter, several material properties were investigated; morphological fiber properties (fiber width, cell wall thickness and fiber coarseness), fines content, carbohydrate monomer composition, and charge density. The results indicate that a thin cell wall and large lumen of the cotton waste fibers affect their higher swelling and retention properties, but further investigation of other morphological, chemical and physical properties of the fibers and fiber networks in pulp sheets is necessary. However, these insights on the behavior of different pulps can already help industries with the optimization of implementation of cotton waste pulps for viscose production.

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.

In the manufacturing of cellulose derivatives, improving cellulose accessibility is essential for achieving a high product quality. In this study, endoglucanase enzyme treatment was applied prior to the cationization reaction to enhance the accessibility of hydroxyl groups for the production of cationized dialdehyde cellulose (CDAC). A range of enzyme dosages (0.09–45.00 ECU/g) was tested, and their effects on the swelling behavior and surface charge density of the final product were evaluated. The surface charge density of the ultimate cellulosic derivative confirmed its cationization and was proven to enhance the charge density of cationized dialdehyde cellulose (35% increase) compared to untreated pulp with enzyme. Additionally, the modified cellulose exhibited a significantly higher swelling capacity than regular pulps. These findings suggest that enzymatic pretreatment can enhance fiber reactivity and support a more sustainable and efficient production of cellulose-based derivatives, offering a promising potential for commercial applications.

Hornification, a complex phenomenon occurring during drying of lignocellulosic materials because of formation of irreversible chemical bonds, remains a subject of scientific interest. This study aims to shed light on the underlying mechanisms of hornification by investigating interactions between the liquid and solid phases through a solvent exchange treatment. The treatment involved replacing water with various solvents in suspensions of never-dried cellulose samples, including alcohols (methanol, ethanol, isopropanol) capable of forming hydrogen bonds, albeit to a lesser extent than water, as well as non-alcohol solvents (acetone, ethyl acetate, toluene, heptane) that do not possess the ability to form chain of hydrogen bond, and no hydrogen bond between each other. The impact of solvents on the hornification process was evaluated using WRV measurements. Our findings reveal that water, as a solvent, plays a dominant role in the hornification process, primarily due to its excellent capability to form bridges of hydrogen bonds. In comparison, hornification with alcohols was considerably lower than with water, likely attributed to the smaller ability of alcohols to engage in such interactions. Furthermore, our results indicate a tendency for reduced hornification also when using non-hydrogen bond solvents with decreased polarity. This strengthens the hypothesis related to chains of hydrogen bonds. Additionally, the interaction between hydrophobic surfaces on cellulose through hydrophobic interactions could provide another plausible explanation.

Polyethylene terephthalate (PET) is one of the most common plastics and can be cascaded mechanically during its life cycle. However, recycling affects the mechanical properties of the material, and the virgin material is constantly in demand. If a worn material could be depolymerized to its chemical building blocks, then a virgin polymer could be generated from old fibers. In this work, we have developed a benign organo-catalytic depolymerization of PET to yield dimethyl terephthalate (DMT) and ethylene glycol (EG) without the need for purification of generated monomers. By recirculating the solvent and organo-catalyst, a solvent/substrate ratio of 3:1 was achieved. The depolymerization was successfully applied to other polyesters, polycarbonates, and polycotton. The cotton isolated from the polycotton depolymerization was successfully processed into viscose fibers with a tenacity in the range of nonwaste cotton-derived viscose filaments. The global warming potential (GWP) of PET depolymerization was evaluated by using life cycle assessment (LCA). The GWP of 1 kg PET recycling is 2.206 kg CO2 equivalent, but the process produces DMT, EG, and heat, thereby avoiding the emissions equivalent to 4.075 kg CO2 equivalent from the DMT, EG, and steam-energy production through conventional pathways. Thus, the net result potentially avoids the emission of 1.88 kg of CO2 equivalent. The impact of this process is lower than that of waste PET incineration and conventional PET recycling technologies.

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.

To make biorefining more environmentally sustainable, preferably residues from forestry should be used and more than one fraction should be upgraded. A third of raw materials from forestry & horbar;tops and branches (T & B)― are either left in the forests or collected and incinerated to a low value. Herein, we apply a fast fractionation to valorize two of the fractions of this forestry residue. The cellulose is converted to textile fibers and all the lignin to hydrocarbons. The environmental sustainability of the novel value chain was studied by life cycle assessment (LCA), and benefits were found in four out of five impact categories. These are important steps to increase fiber production without affecting environmental impact, making biorefining competitive.

Utvecklingskonferensen för Sveriges ingenjörsutbildningar är en nationell konferens för ingenjörsutbildning på högskolor och universitet. Konferensens syfte är att utveckla ingenjörsutbildningarnas kvalitet genom att:

• lyfta fram och dela erfarenheter kring aktuell utveckling av ingenjörsutbildning
• vara en arena för pedagogisk meritering och över tid utgöra ett arkiv för utvecklingen av Sveriges ingenjörsutbildningar
• tillsammans analysera nuläge och utveckla nya möjligheter

Den 24 och 25 november 2021 samlades ledare, lärare, studenter och andra personer med intresse för utveckling inom ingenjörsutbildningar för en tvådagarskonferens på Karlstads universitet.

Temat för årets konferens var:Tillsammans förnyar och förbättrar vi Sveriges ingenjörsutbildningar inför framtidens utmaningar. 

Here, we show that lignin-first biorefining of poplar can enable the production of dissolving cellulose pulp that can produce regenerated cellulose, which could substitute cotton. These results in turn indicate that agricultural land dedicated to cotton could be reclaimed for food production by extending poplar plantations to produce textile fibers. Based on climate-adapted poplar clones capable of growth on marginal lands in the Nordic region, we estimate an environmentally sustainable annual biomass production of ∼11 tonnes/ha. At scale, lignin-first biorefining of this poplar could annually generate 2.4 tonnes/ha of dissolving pulp for textiles and 1.1 m3 biofuels. Life cycle assessment indicates that, relative to cotton production, this approach could substantially reduce water consumption and identifies certain areas for further improvement. Overall, this work highlights a new value chain to reduce the environmental footprint of textiles, chemicals, and biofuels while enabling land reclamation and water savings from cotton back to food production.

A multiple regression model was evaluated to predict pulp and handsheet properties including z-directional tensile strength (z-strength) and Scott bond values. One hypothesis that was central for the model evaluation was that the crill content, as measured with ultraviolet and infrared lights, would improve the statistical models. A chemi-thermomechanical pulp (CTMP) mill designed with two parallel primary refining lines and a reject refiner was the basis for this study, and all process data and pulp samples were gathered from the specific process. Pulp was extracted from the process for an extended period from a position after the latency chest (primary refined pulp) and from the pulp-stream exiting the mill to the board machine (accept pulp). The crill content was positively correlated to the z-strength of the accept pulp, explaining 55% of the variance with a linear regression model with the drill content as the sole predictor. The estimation model of the z-strength of accept pulp was based on a combination of the crill content, freeness, fibril perimeter for longer fibers, and mean kink angle, and resulted in an R-2 of 0.79. When applying cross-validation to determine the predictive model performance, the highest R-2 obtained was 0.67. This latter model included the crill content, fibril perimeter, and mean kink angle as predictors.