Jouni Paltakari

• D.Sc.(Tech)
• Vice Dean (Education) at Aalto University

This study investigates the capabilities of various measurement techniques for quantifying the cellulose content in reject material from a carton recycling center, which consists of polyethylene, cellulose, and aluminum, along with impurities. Different measurement techniques, including Fourier Transform Infrared Spectroscopy combined with Attenuat...

To avoid microplastic pollution, there is an urgent need to replace fossil-based cushioning materials in packaging with easily recyclable alternatives. Here, we investigated the potential of lightweight cellulose fibre materials as a solution for mechanical protection. The quasi-static compression was studied among a vast set of 129 different foam-...

To avoid microplastic pollution, there is an urgent need to replace fossil-based cushioning materials in packaging with easily recyclable alternatives. Here, we investigated the potential of lightweight fibre materials as a solution for mechanical protection. The quasi-static energy absorption properties were studied among a vast set of 129 differe...

Innovations in industrial automation, information and communication technology (ICT), renewable energy as well as monitoring and sensing fields have been paving the way for smart devices, which can acquire and convey information to the Internet. Since there is an ever-increasing demand for large yet affordable production volumes for such devices, p...

In recent years, with the recent advancements in the field of additive manufacturing, the use of biobased thermoplastic polymers and their natural fiber-reinforced biocomposite filaments have been rapidly emerging. Compared to their oil-based counterparts, they provide several advantages with their low carbon footprints, ease of reusability and rec...

We present an affordable, yet accurate and modular camera system solution developed on Raspberry Pi 4/4 GB platform with Raspberry v2.x and HQ camera modules with 8 and 12.3 megapixels still resolutions, respectively. The system uses freely available Python scripts and libraries for digital image processing and non-contact optical measurements unde...

Innovations in industrial automation, information and communication technology (ICT), renewable energy, monitoring and sensing fields have been paving the way for smart devices, which can acquire and convey information to the internet, in every aspect of our lives. Since there is ever-increasing demand for large yet affordable production volumes fo...

The present study concentrates on a series of experiments and numerical analyses for understanding the effects of fiber volume fraction (VF) and draw ratio (DR) on the effective elastic properties of unidirectional composites made from an epoxy resin matrix with a continuous fiber reinforcement. Lyocell-type regenerated cellulose filaments (Ioncell...

Using foam as a carrier fluid in papermaking gives interesting new opportunities. Foam as a more viscous fluid than water is expected to behave differently in a dynamic process. This study presents results obtained under dynamic forming conditions in a semi-pilot scale research environment. Effects of process configurations and running conditions o...

Fibrous materials such as paper, nonwovens, textiles, nanocellulose based-biomaterials, polymer networks and composites are widely used versatile engineering materials. Deformations at the fiber network scale have direct role in their effective mechanical behavior. However, computational description of the deformations is a challenge due to their s...

The largest mechanical pulp production units are high-consistency refiners. In the high-consistency refiners, in-situ measurements of pulp quality are rare. Temperature profile is one of the measurements that is industrially applicable to estimate pulp quality. It measures the steam temperature in the refining area – but how it can detect deteriora...

The use of aqueous foams as a carrier fluid for pulp fibers instead of water has re-emerged in the paper and board industry in recent years. In foam forming, a surfactant is needed to reduce the surface tension of the carrier liquid and to create foam as a process fluid and flowing medium. This presents the following questions: (1) How do the water...

In the original publication of the article, the sentences “Hirasaki and Lawson (1985) found a decrease by almost a factor of 104 occurring in the apparent viscosity of foam (air content 83%) in capillary tubes as the ratio of bubble radius to tube radius, , increased from 0.1 to 10.

Additive manufacturing (AM) has been rapidly growing for a decade in both consumer and industrial products. Fused deposition modeling (FDM), one of the most widely used additive manufacturing methods, owes its popularity to cost effectiveness in material and equipment investment. Current efforts are aimed toward high load-bearing capacity at low ma...

Image processing methods combined with scanning techniques—for example, microscopy or microtomography—are now frequently being used for constructing realistic microstructure models that can be used as representative volume elements (RVEs) to better characterize heterogeneous material behavior. As a complement to those efforts, the present study int...

Phase-separable particulate-containing gel structures constitute complex fluids. In many cases they may incorporate component concentration inhomogeneities within the ensemble matrix. When formulated into high consistency suspensions, these can lead to unpredictable time-dependent variations in rheological response, particularly under shear in simp...

Nowadays, modern nanomaterial research is complemented by machine learning methods to reduce experimental costs and process time. With this motivation, here, we implemented artificial neural network (ANN), random forest (RF), and multiple linear regression (MLR) methods to predict the mechanical properties of three‐component nanocomposite films con...

The bark from fast-growing willow crops contains long and strong sclerenchyma fiber bundles, which could potentially replace the pulp and annual plant fibers currently used to reinforce green polymer composites. Here we successfully demonstrate the isolation of fiber bundles of willow bark with a simple alkali treatment under much milder conditions...

The present study aims at understanding the mechanical and thermal properties of natural fibers in a polymer matrix without strong adhesion between the two constitutes. For this purpose, four types of pulps, which are refined and unrefined pine and birch kraft pulps, were used together with polypropylene without any compatibilizer. One constituent...

The possibility of using cellulose derivative films as (i) insulating material on metal electrodes or (ii) in composite electrode films on metal to produce hot electron-induced electrochemiluminescence (HECL) was studied. It was shown that the luminophores known to produce HECL at thin insulating film coated cathodes (e.g. Si/SiO2 and Al2O3 electro...

Celluloses and nanofibrillar celluloses, and the basis of their luminescence are studied. Comparative studies of photoluminescence of birch kraft pulp and microfibrillar and nanofibrillar celluloses manufactured from the same pulp were made with the aim to investigate their luminescence properties. Comparison was made with the earlier literature an...

We systematically investigated the effect of film-forming polyvinyl alcohol and crosslinkers, glyoxal and ammonium zirconium carbonate, on the optical and surface properties of films produced from TEMPO-oxidized cellulose nanofibers (TOCNFs). In this regard, UV-light transmittance, surface roughness and wetting behavior of the films were assessed....

Conventional coating methods are currently being challenged by newly developed technologies that can result in products with interesting properties and competitive prices. Versatile foam coating is one such promising technology. Foam coating is carried out using different foam application methods, and the viscoelastic nature of the foam allows the...

For fibrous materials such as nonwoven fabrics, paper and paperboards, inter-fiber bonds play a critical role by holding fibers, thus providing internal cohesion. Being a physical phenomenon, inter-fiber bonds occur at every fiber crossing and can be also geometrically detected. In relation to the idea, a statistical geometrical model was developed...

In this study, inkjet printing method was successfully demonstrated to produce catalytic platinum layers for dye-sensitized solar cells. Our work includes meticulous optical, morphological, and electrocatalytical analyses of precisely inkjet-patterned counter electrodes as well as traditionally drop-cast samples. Similar catalytic performance was o...

Carbon based perovskite solar cells are fabricated for the first time in the room temperature environment by employing inkjet infiltration of perovskite precursor ink. The fabricated perovskite solar cells exhibit impressive performance reproducibility with this automated method and exhibit high stability when exposed to 35 °C for a period of 1046...

Current electronic devices are fabricated mostly on glass or plastic films which are often hard to recycle. In this study, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized nano-cellulose (TOCN) film was explored as a green substrate candidate for next-generation electronic applications and its optical, surface and mechanical properties...

Current electronic devices are fabricated mostly on glass or plastic films which are often hard to recycle. In this study, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized nano-cellulose (TOCN) film was explored as a green substrate candidate for next-generation electronic applications and its optical, surface and mechanical properties...

The slow process in which the light absorbing dye molecules are adsorbed from solution on the nanocrystalline TiO2 photoelectrode film has been a handicap to fast and cost-effective fabrication of dye-sensitized solar cells (DSSC) with printing techniques. Here, we report a versatile dye sensitization process, achieved by inkjet printing a concentr...

We successfully inkjet printed an ionic liquid electrolyte in the dye-sensitized solar cell (DSSC) as a part of a new cell fabrication sequence that eliminates drilling holes in the DSSC substrates. The inkjet printing of ionic liquid electrolyte does not only reduce the overall fabrication cost since no additional thermoplastic sealant and glass c...

We successfully inkjet printed an ionic liquid electrolyte in the dye-sensitized solar cell (DSSC) as a part of a new cell fabrication sequence that eliminates drilling holes in the DSSC substrates. The inkjet printing of ionic liquid electrolyte does not only reduce the overall fabrication cost since no additional thermoplastic sealant and glass c...

Micro (MFC) and nanofibrillar (NFC) cellulose materials exhibit strong attraction for water, with the finest fraction acting as superabsorber, swelling to form a gel. This water retaining behaviour has recently been studied in paper and board coating formulations as a replacement for the traditional water retention aid/thickener function of polymer...

The ultimate goal of this project was to develop a practical and economical process for industrial fibrillar cellulose film production. The first aim of the work was to develop a fast and practical method for the production of fibrillated cellulose films for them to be made in minutes instead of hours. In the second stage, films made of different f...

The rheology-related effects of nozzle clogging in inkjet printing can seriously affect ink ejection rate and result in irregular droplet trajectory, resulting in poor printing results. In this study three different inkjet inks, used for functional printing with a Dimatix materials inkjet printer, are investigated rheologically. In connection with...

Pigment coating is an essential unit operation for most high quality papers and boards that are intended to undergo printing. The currently dominating coating techniques are metered size press (MSP) and blade coating with jet, flooded nip, or short dwell-time application, which all have their distinct advantages and drawbacks. A new coating method...

Nano and microfibrillated cellulose (NFC and MFC, respectively, collectively termed MNFC) is known to interact strongly with water, related to its high polarity and surface area. The swelling behaviour acts to form a gel with high water retention properties. The observation that nanocellulose could possibly be used in paper or other coating formula...

Nanocellulose containing materials, such as micro-fibrillated cellulose (MFC) and nanofibrillated cellulose (NFC), are potential additives which could improve strength properties of coated paper and board surfaces and thus substitute natural and synthetic co-binders, such as carboxymethyl cellulose (CMC) and polyacrylic thickeners, in pigmented coa...

Appropriate regularization algorithm is proposed for choosing the regularization parameter based on nosy immobilization viscosity data. Complex fluids as nanocelluose based high consistency suspensions have very complex rheological behavior. This paper describes Tikhonov regularization procedure for reducing the noise from immobilization rheograms...

Current end-user strength requirements for packaging and board grades are progressively becoming more demanding to meet globally. Primarily this is due to the continuous deterioration of recycled furnish quality. Furthermore, the global industrial trend towards cost savings in productivity can only be accomplished by improving drainage and retentio...

The influence of swelling on the rheological and dewatering properties of high consistency nanocellulose based furnishes is considered. Different consistencies of suspensions (1–4 %) and furnishes (5–15 %) were prepared made of two distinctly different grades of nanocellulose containing, micro fibrillated (MFC) and nanofibrillated (NFC) cellulose,...

This paper demonstrates a way to utilize the rheological properties of high consistency microfibrillated and nanofibrillated cellulose (MFC and NFC) based furnishes for improved dewatering. This is relevant to a new manufacturing platform that is being developed to form composite webs from suitable mixtures of MFC or NFC, traditional pulp fibres an...

Darkening of the fines and fiber fraction of peroxide-bleached thermomechanical pulp (TMP) was studied on a laboratory scale using a device that simulates the short circulation of a paper machine. Selected chemicals were dissolved in the circulation water to study the effect of different cations and anions. Ferrous ions darkened the fines and fiber...

This study is part of a broader research aiming at finding out mechanisms and phenomena causing the brightness reduction of mechanical pulp and fillers in the wet end of a paper machine. The main focus of this study was on the darkening of precipitated calcium carbonate (PCC) and precipitated calcium sulfate (PCS) fillers circulating in the short c...

Brightness reduction of mechanical pulp in paper machine water circulations is a well-known phenomenon. However, the reasons behind the darkening are not fully known. The present paper is part of larger study aiming at finding out mechanisms and phenomena causing the brightness reduction of mechanical pulp and fillers in the wet end of a paper mach...

This paper evaluates the humidity effect on the elastic properties and failure mechanism of two types of layered corrugated paperboard structures composed of entirely recycled material and virgin radiata pine (Pinus radiata D. Don) kraft and mixed fibre linerboards and fluting medium. Board samples and their component paper sheets were tested at 50...

Nanotechnology allows development of new enabling technologies with broad commercial potential. Cellulose has also the potential to be the source for renewable materials, which can be made multifunctional and self-assembling at the same time displace many non-renewable materials including metal and ceramics. The potential application area includes...

The paper industry has a strong foothold in the Finnish national economy. Paper mills are one of the key targets for wood procurement companies, and the wood paying capability of a mill is one key factor in determining wood raw material flows. We studied the cost structure of a virtual paper mill, which produces 300,000 air-dry metric tonnes of sup...

Composites from poly(lactic acid) (PLA) and acetylated microfibrillated cellulose (MFC) were prepared by a solvent casting technique. MFC, mechanically isolated from never‐dried bleached birch Kraft pulp, was used as a reinforcement. The acetylation reaction was carried out at 105°C in toluene and proved to be an effective way of increasing the dis...

Brightness reduction of mechanical pulp in paper machine water circulations is a well-known phenomenon. However, the reasons behind the darkening are not fully known. Therefore, in order to simulate the short circulation of a paper machine and to reach a realistic brightness reduction, a laboratory scale methodology was developed. The main focus wa...

The refining of unbleached kraft pulps in their Na+-form has shown energy saving potential. In this study, the fibre network strength of unrefined and laboratory refined samples of an unbleached neverdried kraft pulp in different ionic forms was studied. The external fibrillation and the fibre flexibility were also studied. The objective was to inv...

Nanofibrillated cellulose (NFC) is increasingly utilized in materials and biomedical applications consequently increasing interest in the modification of its surface properties. Besides modification using polyelectrolytes and polysaccharides, NFC can be combined with solid particles enabling formation of fibril network loaded with particles. Use of...

The micro-fibrillated cellulose (MFC) is a potential material which will at least partly substitute the synthetic co- binders, such as carboxymethyl cellulose (CMC), in paper coating color formulations. Co-binders play an important role in controlling both the flow properties and the dewatering rate of coating colors during the application process...

Biocomposites were prepared by solvent casting from poly(vinyl) alcohol and mechanically microfibrillated (MFC) birch pulp. Preparations varied in concentration of polymer solution, mixing time of cellulose/PVA dispersion and were either degassed or not. In addition, specimens were tested in different levels of relative humidity at a constant tempe...

We demonstrate that superhydrophobic and superoleophobic nanocellulose aerogels, consisting of fibrillar networks and aggregates with structures at different length scales, support considerable load on a water surface and also on oils as inspired by floatation of insects on water due to their superhydrophobic legs. The aerogel is capable of support...

: Microfibrillated cellulose (MFC) is known to enhance strength properties of paper. Improved strength usually means increased bonding which is strongly connected to dimensional instability of paper. The main objective of this work was to evaluate the dimensional stability of wood-free paper containing different amounts of varying grades of MFC and...

The paper presents test results on wet pressing of paper sheets containing various proportions of different and modified non-wood pulps. The kraft eucalyptus pulp used in the paper sheets was partly substituted by various amounts of non-wood pulps, while the kraft pine pulp content was kept constant at 20% in the sheets. The dewatering test results...

BioResources Vol.5 Nr.2, 1164-1177 In this study it was shown that the enzymatic removal of xylan from ECF-bleached birch kraft pulp enhances the water removal from the pulp, especially in the late stages of pulp drying. The effect of xylanase treatments on dewatering was clarified by using a moving belt former (MBF), a press simulator (MTS) and an...

The increasing use of coated papers in general, but even more so in digital printing methods, reinforces the need for the properties of paper coatings to be well understood. Especially, a more detailed knowledge of the thermal properties of coatings can contribute to improved print quality and process economy of electrophotography and offset printi...

Thermal conductivity of paper coatings is increasingly important in the performance of many printing processes, including traditional heatset web offset and thermal papers, as well as digital processes, such as electrophotography. This work studies the extension of a Modified Lumped Parameter Model, previously used successfully to describe talc coa...

The influence of different polymers on the aggregation tendency of cellulose microfibril suspension was evaluated with optical microscopy. The aggregation tendency of fibril suspensions was compared with aggregation behavior of surface fibrils on fibers by different polymers. The material properties of fiber bonding domain were evaluated by mechani...

Thermal conductivity of paper coating structures can be regarded as an important property for many processes involving the application of thermal energy on coated papers. This work analyses the thermal conductivity of coatings in terms of their structure. A Monte Carlo simulation-based particle deposition was used to create idealised two-dimensiona...

This study investigates the changes in fine paper properties through structural changes when the standard base furnish is altered from fibres alone to microfines and pigments. In this study, PCC (precipitated calcium carbonate) was used as the pigment. The new composite paper concept enables us to load upto 50% -60% PCC in fine paper. The new compo...

This study examines the properties of cellulosic fibrillar fines manufactured from different pulp raw materials, bleached softwood kraft (bswk), themomechanical (TMP), and non-wood sisal. Chemical characterisation showed that the carbohydrate and lignin contents of sisal were between those of bswk and TMP. Sisal was found to contain about three tim...

For printing on coated papers, better knowledge of the thermal properties of coatings can be beneficial. Currently, little data on thermal properties of coatings exist, partially because of the complexity of measurement associated with thin porous layers. This work elaborates on a method to study thermal diffusivity by the measurement of temperatur...

Most optical standards of the paper industry take into account only lightness of the object and ignore hue and saturation. This may be adequate for evaluating black print and white paper, but it is not for coloured prints or papers. Recently, it was found that, unlike standard definitions of opacity, a colour difference model is able to predict the...

Polymeric and activated carbon composite membranes were prepared and their morphology quantitatively, tensile properties and performance (flux and cut-off) were characterized.Both types of membranes were prepared by using polysulfone and di-methyl formamide as polymer and solvent, respectively. In order to obtain a wide range of morphologies, two n...

The effects of polyelectrolyte complexes (PECs) of anionic and cationic Polyacrylamide (A-PAM and C-PAM) on papermaking were studied. The Polyacrylamides had different molecular weights and charges, so the complexes varied in size and density. A laboratory-scale system that realistically simulates the wire, press and dryer sections was used. Retent...

The effect of press drying on the sheet properties of HT-CTMP (high-temperature CTMP) was determined. In the HT-CTMP process, preheating and refining are carried out at high temperature (above 165°C). The energy consumption is very low, but the resulting fibres have poor bonding ability due to the lignin coating on the fibre surface. One potential...

The objective of this study was to find out how much press drying improves the properties of high-temperature thermomechanical pulp (HTMP) sheets. It is well known that HTMP, which is also known as Asplund pulp, can be manufactured with low energy consumption (0.2 to 0.4 MWh/t). HTMP fibres are coated by lignin, which makes them stiff and hydrophob...

A study was conducted to determine how much press drying improves the properties of high-temperature thermomechanical pulp (HTMP) sheets. For this purpose, HTMP handsheets were press-dried with different initial moisture contents. The effect of moisture content on the glass transition temperature of HTMP was also examined. It was found that only a...

In this paper an inexpensive configuration for a cylinder blow box (CBB) and its effect on the evaporation rate are described. The objective of this work was to determine the effect of the blow boxes on drying intensity on a paper machine. The pilot machine trials were simulated with a computer program. Based on these results two cases were simulat...