Production of low-density and high-strength paperboards by controlled micro-nano fibrillation of fibers

One of the critical challenges in the fber-based packaging industry is to produce low-density paperboards with high functionality and atractive cost structure. In this study, we examine how control of the hierarchical fber swelling can be used to enhance bonding and generate a low-density fber network with excellent strength properties. Here, the osmotic pressure inside the cell wall is increased by adding phosphate groups with a deep eutectic solvent (DES) functional drying method. Together with mechanical refning, this process causes the fbril aggregates to split and swell up massively. This efect was measured by a novel thermoporosimetry analysis method. The treated fbers have enhanced external fbrillation, fbrillar fnes and bonding potential. When mixed with relatively stif, unrefned fbers, a well-bonded sheet with lower density than a conventionally refned reference sheet was achieved. The results suggest that pulp fbers can be “nanoengineered” to enhance performance without the complications of producing and adding nanocellulose

E. Globulus Vessel and Fibre Chemical Analysis

Hardwood species have a complex cellular structure consisting of fibres, vessel elements and parenchyma cells with different chemical compositions. However, the presence of vessels with significant dimensions in their structure is a recurrent problem in the operation of industrial UWF paper printing. Since the 1980s, vessel picking and ink refusal are problems that paper professionals have tried to solve, but solutions for these have not yet been fully found. If vessels are concentrated in a stream, they can be pre-treated (e.g., by mechanical refining) and reincorporated into the pulp. Other strategies aim at vessel enzymatic and/or chemical passivation and sheet surface chemical treatment, altering the vessel adhesion to the fibre network. This requires vessel concentration at laboratorial level for proper chemical studies, such as FE-SEM, μ-XPS, TOF-SIMS and μFTIR. The main objective of our experimental study was to examine bleached kraft pulp E. globulus vessel and fibre composition. For this we performed EDX and μ-FTIR analysis on both fibre and vessel elements, and obtained the carbohydrate composition, the total acids content, the hexenuronic acids content and the zeta potential. Keywords: E. globulus, vessel, EDX, μ-FTIR, sugar content, zeta potentia

Mapping Nanocellulose- and Alginate-Based Photosynthetic Cell Factory Scaffolds:Interlinking Porosity, Wet Strength, and Gas Exchange

To develop efficient solid-state photosynthetic cell factories for sustainable chemical production, we present an interdisciplinary experimental toolbox to investigate and interlink the structure, operative stability, and gas transfer properties of alginate- and nanocellulose-based hydrogel matrices with entrapped wild-type Synechocystis PCC 6803 cyanobacteria. We created a rheological map based on the mechanical performance of the hydrogel matrices. The results highlighted the importance of Ca2+-cross-linking and showed that nanocellulose matrices possess higher yield properties, and alginate matrices possess higher rest properties. We observed higher porosity for nanocellulose-based matrices in a water-swollen state via calorimetric thermoporosimetry and scanning electron microscopy imaging. Finally, by pioneering a gas flux analysis via membrane-inlet mass spectrometry for entrapped cells, we observed that the porosity and rigidity of the matrices are connected to their gas exchange rates over time. Overall, these findings link the dynamic properties of the life-sustaining matrix to the performance of the immobilized cells in tailored solid-state photosynthetic cell factories.</p

Changes in the hygroscopic behavior of cellulose due to variations in relative humidity

Details on how cellulosic surfaces change under changing moisture are incomplete and even existing results are occasionally neglected. Unlike sometimes reported, water adsorption is unsuitable for surface area measurements. However, water can be utilized for assessing surface dynamics. Hygroscopic changes of pulp and bacterial cellulose were studied by dehydrating the samples in a low polarity solvent and then introducing them into a moist atmosphere in a dynamic vapor sorption (DVS) apparatus at 0-93% relative humidity (RH). The DVS treatment caused hygroscopicity loss near applied RH maxima, however, the hygroscopicity increased at RH values > 10-20% units lower. Additionally, the hygroscopic changes were partially reversible near the RH maximum. Therefore the hygroscopicity of cellulose could be controlled by tailoring the exposure history of the sample. Hornification reduced these changes. The observations support reported molecular simulations where cellulose was shown to restructure its surface depending on the polarity of its environment.Peer reviewe

Consolidation and dewatering of a microfibrillated cellulose fiber composite paper in wet pressing

Peer reviewe

General overview of graphene: Production, properties and application in polymer composites

Graphene is a new and exciting material that has attracted much attention in the last decade and is being extensively explored because of its properties, which have been described with so many superlatives. Production of graphene for large scale application is still a major challenge. Top-down graphene exfoliation methods from graphite, such as liquid-phase exfoliation which is promising because of low cost and high scalability potential will be briefly discussed. We also analyze the challenges and possibilities of using graphene as a nanofiller in polymer composites which has resulted in enhanced electrical, mechanical and thermal properties. In this review, we take a panoramic approach to give insight on the different aspects of graphene such as properties, graphite-based production methods and also examples of graphene application in polymer composites and which will be beneficial to both novice and experts.Peer reviewe

High-concentration shear-exfoliated colloidal dispersion of surfactant–polymer-stabilized few-layer graphene sheets

To exploit the remarkable properties of graphene fully, an efficient large-scale production method is required. Sonication-assisted liquid-phase exfoliation of graphite, for example, has been extensively used for the production of few-layer graphene sheets, but suffers from low efficiency and high energy consumption and thus is not viable for large-scale production. Here we demonstrate a method that is more efficient and has higher scalability potential than sonication. We show that a few-layer graphene at high concentration of up to 1.1 mg ml−1 can be achieved in aqueous-based medium by highly efficient shear exfoliation of graphite in a processing time of just 2 h. The exfoliation process was carried out in a commercially available high shear colloidal mixer fixed with a three-stage rotor–stator shear generator for optimum exfoliation with a continuous circulation system. The high efficiency and a significant improvement over sonication adopting our method were demonstrated by the fact that the conversion to few-layer graphene sheets produced after just 30 min by shear exfoliation required, in contrast, 100s of hours by sonication. High-concentration defect-free few-layer graphene in aqueous medium, produced at short shearing time, demonstrates that this method has high potential for large-scale production. The produced graphene films exhibit additionally a high electrical conductivity of about 29000 S m−1.Peer reviewe

Twin-roll forming, a novel method for producing high-consistency microfibrillated cellulosic films

Funding Information: Open Access funding provided by Aalto University. This work was supported by Jane and Aatos Erkko foundation (3269-7422e).Micro-nano fibrillated cellulose (MNFC) films have the potential for applications in, e.g., packaging and printed electronics. However, the production paradigm for these types of products has still not been established. This study uses twin-rollers to form films from high consistency (15% w/w) micro fibrillated cellulose furnishes. MFC furnishes were produced at 20% wt dry matter content with enzymatic hydrolysis and PFI refining. We used the twin-roller method to spread the material over a supporting substrate by repeatedly passing between two parallel rollers with decreasing nip. Rheological behavior and physical properties of furnishes were analyzed. We found that only some furnishes with relatively short fiber lengths were formable. Refining improved the formation of the sheets. Roll-formed sheets showed comparable strength and formation to conventional wet-laid hand sheets.Peer reviewe