| 51. |
- Karlström, Anders, et al.
(author)
-
Pulp property development Part I: Interlacing under-sampled pulp properties and TMP process data using piece-wise linear functions
- 2015
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 30:4, s. 599-608
-
Journal article (peer-reviewed)abstract
- Thermo-Mechanical Pulp (TMP) refiners served in this work as an example of how to combine oversampled and undersampled variables on a common timeframe for further analysis.To get more information from the refining process, temperature measurement arrays in the refining zones were studied alongside process measurements such as motor load, production rates, plate gaps, dilution waters, pulp properties and manually measured blow-line consistency.The undersampled data set consisted of 63 laboratory samples obtained at a Swedish TMP mill, which were tested for tensile index, mean fiber length and Somerville shives content. The pulp samples were obtained at five different periods during three months to cover a large dynamic operating window.The data set was expanded using a piece-wise linear approach. The measurements inside the refining zone were shown to be important variables when interlacing the undersampled pulp properties with the oversampled process data set, consisting of 350 000 samples.Use of an extended entropy model provided a palette of information about the process conditions inside the refining zone. Particularly, the residence time and the consistency in the refining zones were essential for the pulp property development, as a link between the refining segment pattern used and the current state of refiner operation.
|
|
| 52. |
- Karlström, Anders, 1958, et al.
(author)
-
Pulp property development Part I: Interlacing under-sampled pulp properties and TMP process data using piece-wise linear functions
- 2015
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 30:4, s. 599-608
-
Journal article (peer-reviewed)abstract
- Thermo-Mechanical Pulp (TMP) refiners served in this work as an example of how to combine oversampled and undersampled variables on a common timeframe for further analysis. To get more information from the refining process, temperature measurement arrays in the refining zones were studied alongside process measurements such as motor load, production rates, plate gaps, dilution waters, pulp properties and manually measured blow-line consistency. The undersampled data set consisted of 63 laboratory samples obtained at a Swedish TMP mill, which were tested for tensile index, mean fiber length and Somerville shives content. The pulp samples were obtained at five different periods during three months to cover a large dynamic operating window. The data set was expanded using a piece-wise linear approach. The measurements inside the refining zone were shown to be important variables when interlacing the undersampled pulp properties with the oversampled process data set, consisting of 350 000 samples. Use of an extended entropy model provided a palette of information about the process conditions inside the refining zone. Particularly, the residence time and the consistency in the refining zones were essential for the pulp property development, as a link between the refining segment pattern used and the current state of refiner operation.
|
|
| 53. |
- Karlström, Anders, 1958, et al.
(author)
-
Pulp property development Part II: Process non-linearities and their influence on pulp property development
- 2016
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 31:2, s. 287-
-
Journal article (peer-reviewed)abstract
- It is shown in this paper that knowledge of the spatially measured temperatures inside the refining zone in TMP refiners is essential in describing non-linear dynamics of high consistency refining. By expanding the pulp and handsheet properties using piece-wise linear functions into the time domain, an auto-regressive model can be applied to verify that the tempera-ture and the consistency profiles, in combination with the motor load and production rate, are key input candidates when modeling changes in different pulp properties. The model accuracy is analyzed using process information captured at different time and operating conditions. It is also shown that it is more complex to estimate and validate the tensile index than the mean fiber length and Somerville shives content, especially close to refiner operating limits where a shift in the process gain may occur. This type of switched dynamics in tensile index estimation at a specific consistency is related to non-linear behaviors where the fiber pad distribution most likely undergoes a local collapse.
|
|
| 54. |
- Karlström, Anders, 1958, et al.
(author)
-
Pulp property development Part III: Fiber residence time and consistency profile impact on specific energy and pulp properties
- 2016
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 31:2, s. 300-307
-
Journal article (peer-reviewed)abstract
- This paper focuses on the pulp properties obtained from ThermoMechanical Pulp (TMP) CD refiners. Undersampled pulp variables are expanded into an oversampled set of process data, which makes it possible to analyze pulp properties in a dynamic time frame. It is shown that, in order to gain deeper insight into the defibration/fibrillation at a specific energy input, one needs to know the fiber residence time and the consistency profile. Moreover, the fiber residence time in the flat zone (FZ) and conical zone (CD) are intertwined with the consistency out from FZ and CD. Together with an external variable (production), these internal variables are essential for predicting the pulp properties. It is also shown that internal process conditions from different test series can be manipulated in the operating window using a low-frequency gain description obtained from an ARX model. The same mapping procedure can be applied to pulp and handsheet properties (in this paper represented by the tensile index), and this opens for implementation of new optimization routines to find more energy efficient operating points while maintaining pre-specified pulp quality.
|
|
| 55. |
- Karlström, Anders, 1958, et al.
(author)
-
Refiner optimization and control Part III: Natural decoupling in TMP refining processes
- 2015
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 30:3, s. 417-425
-
Journal article (peer-reviewed)abstract
- In TMP-refining processes, the stabilization of the fiber pad inside the refining zone requires a new control approach. Specific energy control tends to be complex and most often affected by a number of disturbances not so well specified in traditional MPC-concepts. To describe the dynamics in such nonlinear processes is difficult, tedious and requires significant maintenance support. This paper focuses on two important issues related to modeling in mechanical pulping processes: measurements of internal states inside the refining zone and in particular natural decoupling to find a model suitable for future process optimization and improved control concepts of complete refiner lines. The idea is to show how this complex process, with serially linked refiners or refining zones, can be modeled and controlled using a simplified process description. In this series of papers, data from a commercial Twin-refiner and a CD-refiner are available as inputs. As an example of internal state measurements, refining zone temperature profiles and estimated distributed consistency in the refining zone are used. We show that the characteristics of the temperature profile dynamics makes it possible to introduce a decoupling scheme where the anti-diagonal elements in the transfer function matrix describing the process can be eliminated naturally, independent of which refiner is to be controlled.
|
|
| 56. |
- Karlström, Anders, 1958, et al.
(author)
-
Refiner optimization and control Part IV: Long term follow up of control performance in TMP processes
- 2015
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 30:3, s. 426-435
-
Journal article (peer-reviewed)abstract
- This paper focuses on three important issues; Process understanding in relation to control of nonlinear processes; Natural decoupling by using internal state measurement devices; Long term follow up procedures of process control investments. As an example, a new control system for Thermo Mechanical Pulp (TMP) refiners is used, based on a cascaded control structure. The internal states, in this case the refining zone temperature profiles, are controlled in the inner loop whereas the outer loop handles pulp properties. The characteristics of the temperature profile dynamics makes it possible to introduce a decoupling scheme where the anti-diagonal elements in the transfer function matrix describing the process, can be eliminated naturally. The system can handle several pulp propertied simultaneously but in this study mean fiber length (MFL) is the target variable. The process is followed about 200 days in manual mode control and 200 days in automatic mode. It is shown that the standard deviations in the pulp property variables freeness (CSF) and MFL were decreased about 40 and 60%, respectively. Significant reductions in variability of shives and a motor load standard deviations was achieved. On top of this, an increased production was obtained and the control system runnability was raised from 50% to 98%, levels that are far from commercial MPC-control concepts in TMP refining control.
|
|
| 57. |
- Kettil, Gustav, 1990, et al.
(author)
-
Numerical investigation of upstream cylinder flow and characterization of forming fabrics
- 2019
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 34:3, s. 371-393
-
Journal article (peer-reviewed)abstract
- In this work, the fundamentals of upstream flow over cylinders and forming fabrics are investigated, and measures for characterization of fabrics are proposed. Two-dimensional flow over one cylinder, two cylinders, and one and two rows of cylinders, are analysed numerically. By studying different configurations and various Reynolds numbers, the upstream flow features are characterized. It is concluded that cylinders have a short range of upstream flow impact, shortest for rows of cylinders with small spacings. For R e - [ 10, 80 ]Re\in [10,80], the Reynolds number dependency is weak. It is shown that a downstream row positioned in tandem has negligible impact on the upstream flow, while a displaced second row influences the upstream flow if the spacing in the first row is larger than one diameter. The pressure drop required to drive the flow over the cylinders depends non-linearly on the porosity of the configuration. Flow measures of the upstream flow are proposed, which in addition to the volume flow per area are used to characterize fabric flow properties. The conclusions from the cylinder study also hold for industrial fabrics, and it can be explained how properties of the fabric influence the final paper. The wave-length of flow periodicity is studied in relation to drainage marking. This study demonstrates that simulations can greatly improve pure experimental-based fabric characterization. © 2019 Walter de Gruyter GmbH, Berlin/Boston.
|
|
| 58. |
|
|
| 59. |
- Li, Dongfang, et al.
(author)
-
From forest residues to hydrophobic nanocomposites with high oxygen-barrier properties
- 2016
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 31:2, s. 261-269
-
Journal article (peer-reviewed)abstract
- A biorefinery of forest resources should be able to convert all components of trees, including the bark and other types of forest residues, into value-added products. Here, non-cellulosic polysaccharides (NCPs) isolated from Norway spruce bark and cellulose nanocrystals (CNCs) isolated from the logging residues of Norway spruce were mixed to prepare nanocomposites with competitive thermo-mechanical properties. Polyepoxy acid (PEA) derived from a monomer of suberin in birch bark was used as a coating on the nanocomposites to develop functional materials entirely based on forest resources. All of the PEA-coated nanocomposites were hydrophobic. At 50% and 80% relative humidity, they showed high oxygen-barrier properties that were comparable to or even better than those of some renewable materials such as xylan-, galactoglucomannan- and nanofibrillated cellulose-based films and synthetic materials such as polyvinylidene chloride and polyamide.
|
|
| 60. |
|
|
| 61. |
- Lindström, Tom, et al.
(author)
-
On the nature of joint strength of paper : Effect of dry strength agents - Revisiting the Page equation
- 2016
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 31:3, s. 459-468
-
Journal article (peer-reviewed)abstract
- This report deals with the effects of various chemical-treatments - carboxymethylcellulose-grafted (CMC) pulp in different ionic forms (Na+, Ca2+, and Al3+), cationic starch, anionic polyacrylamide, and microfibrillated cellulose (MFC) as well as PFI-refining on the strength properties of never-dried bleached soft-wood kraft pulp. The general in-plane strength properties were measured together with z-strength and interlaminar shear strength. The sheet density was varied by pressing the wet sheets to various dry solids content. The relative bonded area of the sheets was determined by the BET surface area of the sheets using krypton adsorption. Interlaminar shear strength is introduced as a measure for fibre-fibre bond strength and validates its use in the Page equation from first principles and it was shown to hold over a large range of tensile strengths. Only at very high tensile index values the calculated tensile index deviated from measured tensile index. This was most likely due to a shift from adhesive to cohesive failure of the joint. The various strength reinforcement methods used were all based on carbohydrate based additives and for those additives the specific joint strength was found to be independent of the specific additive, so the strength reinforcement is only related to the increased relative bonded area upon the addition of the strength adjuvant, although the additives consolidate the sheet on various structural levels.
|
|
| 62. |
- Linvill, Eric, 1989-, et al.
(author)
-
Biaxial In-Plane Yield and Failure of Paperboard
- 2016
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 31:4, s. 659-667
-
Journal article (peer-reviewed)abstract
- Paperboard is oftentimes subjected to biaxial in-plane stress and strain states, although very few experimental studies of the biaxial in-plane yield and failure of paperboard have been conducted. A new biaxial testing method to determine the in-plane stress- and strain-based yield and failure surface of paperboard was proposed and implemented. The method utilized cruciform specimens containing a reduced-thickness region (prepared by laser engraver) to increase probability of failure in that region, and digital image correlation was utilized to measure strain. The obtained stress-based failure surface was similar to previously reported results in the literature, but the obtained strain-based failure surface differed from the one previously reported strain-based failure surface. The obtained yield and failure surfaces had similar shape, providing confidence in both results due to the related deformation and failure mechanisms in paperboard. Furthermore, the overall shape of the stress- and strain-based yield surfaces was unaffected by the definition of the yield point. The obtained strain-based failure surface revealed the forming limits and therefore strengths and limitations of various 3-D forming methods for paperboard.
|
|
| 63. |
- Lundberg, Mathias, et al.
(author)
-
Validation of crill measurements in a high-yield pulp refining process for improved fines material control
- 2018
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:2, s. 200-209
-
Journal article (peer-reviewed)abstract
- In high-yield pulp (HYP) refining, fine material is created by peeling action on the fibre surface. This fine material is usually characterized using conventional camera technology and image analysis. The smallest particles, the crill, also created in the refining process are too small to be visible in a camera image, and are therefore measured using light sources in the UV and IR wavelength spectrum. This research sought to determine whether the crill could be characterized in the presence of large fines material in a HYP refining process, and the results indicated that the larger fines material had little impact. In addition, the variation in crill measurements declined as the fibre treatment increased and remained low and stable during an extended period. Due to the great need to monitor and control pulp processes using rapid online measurements, cost-reduction actions at mills running close to specification targets put high demands on the measuring devices characterizing the production. The outcome of this study enables the use of the crill method to improve our knowledge of fibre treatment and its contribution to fibre adhesion in complex refining processes. Finally, combining conventional camera technology and the crill method could improve the overall fines material control.
|
|
| 64. |
- Magnusson, Mikael S.
(author)
-
Investigation of interfibre joint failure and how to tailor their properties for paper strength
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : AB Svensk Papperstidning. - 0283-2631 .- 2000-0669. ; 31:1, s. 109-122
-
Journal article (peer-reviewed)abstract
- The key property for the load carrying capacity of paper materials is the interfibre joint strength. Due to the difficulty of testing the strength of such microscopic entities, the typical approach is to test isolated fibre-fibre crosses. In such experiments the joint is but one component of the tested structure and the flexural compliance of the long fibre segments results in a mixed mode of loading. Furthermore, the details of the failure mechanisms of such joints are as of yet unknown. A continuum description of the paper sheet is often insufficient to explain governing mechanisms when properties of the underlying structure are changed by mechanical or chemical modifications. Therefore network models are often used to take into account the underlying mechanisms. However, network models in turn rely on the properties of the fibres and of the interfibre joints. This paper aims to characterize the damage behaviour of isolated fibre-fibre crosses from three approaches: identifying typical damage features from an extensive number of mechanical tests of isolated fibre-fibre crosses; study the applicability of using cohesive zones to model the failure behaviour of inter-fibre joints; and, to study the influence of fibre and joint properties to the load carrying capacity of fibre-fibre crosses. The results indicate that the strength in the normal direction is significantly lower than in the shear direction and means on how to tailor the properties of fibres and joints for increasing the load carrying capacity is suggested.
|
|
| 65. |
- Marais, Andrew, et al.
(author)
-
Pilot-scale papermaking using Layer-by-Layer treated fibres; comparison between the effects of beating and of sequential addition of polymeric additives
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:2, s. 308-314
-
Journal article (peer-reviewed)abstract
- The Layer-by-Layer (LbL) deposition technique was used to treat fibres before papermaking on a pilot scale. Following a laboratory pre-study performed earlier to determine the adsorption isotherms and the kinetics of formation of multilayers of polyamideamine epichlorydrine (PAE) and carboxymethylated cellulose (CMC) on unbeaten, bleached softwood fibres, online LbL treatment of the furnish was carried out on the EuroFEX pilot paper machine. Papers from fibres coated with up to four layers of polyelectrolytes were produced. Two different LbL systems were investigated, with anionic CMC in combination with either PAE or cationic starch (CS). The results showed that the mechanical strength of the paper significantly increased when the fibres were LbL-treated online. A comparison with conventional beating of the fibres revealed that the LbL treatment was a potential substitute to beating treatment, as the density of the LbL-treated papers remained constant while the mechanical properties were significantly improved. At the same time, the press solids content was significantly higher (2%) when using LbL-treated fibres than with beaten fibres.
|
|
| 66. |
- Mattsson, Amanda, et al.
(author)
-
New strength metrics for containerboards : Influences of basic papermaking factors
- 2018
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:4, s. 592-602
-
Journal article (peer-reviewed)abstract
- In end-use, containerboard is subjected to a variety of loading histories, such as seconds of loading/unloading, hours of vibration, days of creep load. The fundamental question is whether the commonly measured static strength represents “strength” under these conditions. Another question is, since those time-dependent failures are notoriously variable, how to describe the probabilistic aspect. This study concerns the characterisation of these different facets of “strength”. In our earlier work, we have investigated the theoretical framework for time-dependent, probabilistic failures, and identified three material parameters: (1) characteristic strength, Sc, representing short-term strength, (2) brittleness/durability parameter, ρ, and (3) reliability parameter, β. We have also developed a new method that allows us to determine all these parameters much faster than typical creep tests. Using the new method, we have started investigating effects of basic papermaking variables on the new material parameters. Among the samples tested, the parameter ρ varied from 20 to 50, and β from 0.5 to 1.0. This suggests that, even within the current papermaking practice, there is a wide operating window to tune these new material parameters. The future work is, therefore, to find specific manufacturing variables that can systematically change these new material parameters.
|
|
| 67. |
- Medronho, Bruno, et al.
(author)
-
Probing cellulose amphiphilicity
- 2015
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 30:1, s. 58-66
-
Journal article (peer-reviewed)abstract
- Cellulose dissolution and regeneration is an increasingly active research field due to the direct relevance for numerous production processes and applications. The problem is not trivial since cellulose solvents are of remarkably different nature and thus the understanding of the subtle balance between the different interactions involved becomes difficult but crucial. There is a current discussion in literature on the balance between hydrogen bonding and hydrophobic interactions in controlling the solution behavior of cellulose. This treatise attempts to review recent work highlighting the marked amphiphilic characteristics of cellulose and role of hydrophobic interactions in dissolution and regeneration. Additionally, a few examples of our own research are discussed focusing on the role of different additives in cellulose solubility. The data does support the amphiphilic behavior of cellulose, which clearly should not be neglected when developing new solvents and strategies for cellulose dissolution and regeneration.
|
|
| 68. |
- Melo Filho, Alberto, et al.
(author)
-
Heat-killing of Legionella in biological sludge from a paper and pulp mill water treatment plant
- 2015
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 30:1, s. 121-125
-
Journal article (peer-reviewed)abstract
- Paper and pulp mills use biological water treatment plants to reduce Chemical Oxygen Demand (COD) release to the environment. In the end of the process, microorganisms are concentrated into a biological sludge. Among the microbes thriving in these plants are Legionella, causing the Legionnaires disease. Combustion of the biological sludge produced at a plant results in unwanted downstream effects on the production and probably increased formation of nitrogen oxides (NOx) in the recovery boiler. Due to the disadvantages of combustion, the possibility to sterilize biological sludge has been investigated as a part of the continuously ongoing work at Metsa to improve occupational safety and reduce impact on the environment in a proactive way. A method to eradicate Legionellae in biological sludge would improve safety and ecological sustainability if the sludge instead is safely composted and used as e.g. soil fertilizer. Here we have assessed the time to death upon sludge heat treatment of a pathogenic L. pneumophila serogroup 1 strain, a L. longbeachae strain and the bacteria naturally occurring in biological sludge at the Metsa Board, Husum mill, Sweden. Time to death decreased with increasing temperatures up to 65 degrees C, where higher temperatures resulted in neglectable gain in time to death.
|
|
| 69. |
- Mesic, Behudin Beko, et al.
(author)
-
Latex-based barrier dispersion coating on linerboard : Flexographic multilayering versus single step conventional coating technology
- 2015
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 30:2, s. 349-359
-
Journal article (peer-reviewed)abstract
- The aim of this study was to investigate the possibility of using the flexographic printing process for the deposition of multilayered latex-based barrier dispersion coatings on linerboard to improve its moisture barrier properties. A coating formulation developed for a conventional coater has been tested using a flexographic printing web press. The performance of multi-layering of up to six layers was compared with a single step conventional coating process in terms of runnability and barrier performance. A commercial linerboard was used as substrate for both processes. The coated linerboard samples were examined using scanning electron microscopy and surface profiling, and were characterized with respect to their coating grammage, WVTR and water absorption (Cobb(120)) properties. The impact of waxes on water absorption was also investigated for the two coating strategies. The results show that for a similar total coating grammage ( about 6 g m(-2)), samples coated using the flexographic press showed better barrier performance and less cracks on the coated surfaces than samples coated using a conventional coating process.
|
|
| 70. |
- Moser, Carl, 1987-, et al.
(author)
-
Improved dispersibility of once-dried cellulose nanofibers in the presence of glycerol
- 2018
-
In: Nordic Pulp & Paper Research Journal. - Berlin : De Gruyter Open. - 0283-2631 .- 2000-0669. ; 33:4, s. 647-650
-
Journal article (peer-reviewed)abstract
- To investigate the dispersibility of dried cellulose nanofibers (CNFs), various additions (glycerol, octanol, glycol, and sodium perchlorate) were added to CNFs prior to drying. Glycerol was the only species to show any significant effect on re-dispersibility. The sedimentation was slower, and the transmittance of the solution was comparable to that of its undried counterpart. Increasing the amount of glycerol showed a clear trend with regard to dispersibility. The mechanical properties of films were maintained for samples that were dried and redispersed in the presence of glycerol.
|
|
| 71. |
- Moser, Carl, 1987-, et al.
(author)
-
Xyloglucan adsorption for measuring the specific surface area on various never-dried cellulose nanofibers
- 2018
-
In: Nordic Pulp & Paper Research Journal. - Berlin : De Gruyter Open. - 0283-2631 .- 2000-0669. ; 33:2, s. 186-193
-
Journal article (peer-reviewed)abstract
- In this paper, we explore xyloglucan adsorption to cellulose nanofibers as a method for the evaluation of their quality (i. e., the degree of disintegration) and the accessible surface area in the wet state and at low ionic strength. This method was shown to be capable of estimating the surface areas of 14 different cellulose nanofiber qualities from both hardwood and softwood with different pretreatments, including enzymatic hydrolysis using a monocomponent endoglucanase, TEMPO-mediated oxidation, and carboxymethylation. The cellulose surface measured using this method showed a correlation with the degree of disintegration expressed as transmittance for different concentrations of xyloglucan.
|
|
| 72. |
- Moser, Carl, 1987-, et al.
(author)
-
Xyloglucan for estimating the surface area of cellulose fibers
- 2018
-
In: Nordic Pulp & Paper Research Journal. - Berlin : De Gruyter Open. - 0283-2631 .- 2000-0669. ; 33:2, s. 194-199
-
Journal article (peer-reviewed)abstract
- The hemicellulose xyloglucan can be utilized to measure exposed cellulose surfaces for pulp fibers. This was shown by correlating a refining series with the adsorbed amount of xyloglucan, and by swelling cellulose fibers to various degrees by increasing the charge density. The method is specific to cellulose and could be used to quantify refining or to determine hornification.
|
|
| 73. |
- Mörseburg, Kathrin, et al.
(author)
-
ATMP refining of Norway spruce - Defibration characteristics and fibre wall properties
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:3, s. 386-400
-
Journal article (peer-reviewed)abstract
- Defibration and fibre development patterns were investigated for the novel ATMP refining process, based on pilot scale trials with Norway spruce chips. ATMP refining with different chemical agents was compared to RTS refining with and without Impressa-finer (RT) and Fiberizer (F) pre-treatment. RT-F pre-treatment significantly improved both initial defibration, axial fibre splitting and fibre flexibility, compared to RTS primary stage refining without pre-treatment. Both types of investigated ATMP process chemistry - hydrogen peroxide combined with magnesium hydroxide under alkaline conditions (P) or acid sodium bisulphite (S) added to the primary refiner dilution water - further improved the fibre separation of RT-F pre-treated wood during primary stage RTS refining. This is largely attributed to enhanced fibre swelling. S-treatment facilitated frequent fibre separation within or close to the S2 wall layer, yielding extremely low shive levels and well-fibrillated, thin-walled fibres early in the process. S-treatment also rendered stiffer fibres, which made them susceptible to breakage, axial splitting and internal delamination. P-application is proposed to affect primarily the interior layers of the fibre walls, facilitating rapid fibre wall swelling towards the lumen, fibre softening and flexibilization.
|
|
| 74. |
- Naderi, Ali, et al.
(author)
-
A comparative study of the properties of three nano-fibrillated cellulose systems that have been produced at about the same energy consumption levels in the mechanical delamination step
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:3, s. 364-371
-
Journal article (peer-reviewed)abstract
- The viscosity, tensile strength- and barrier properties of enzymatically pre-treated- (NFCEnz), carboxymethylated- (NFCCarb) and carboxymethyl cellulose (CMC) modified (NFCCMC) nanofibrillated cellulose systems (NFC) that have been produced at about the same energy consumption levels in the mechanical delamination step in the manufacturing of the different NFCs are reported. It was found that NFCEnz and NFCCMC are characterized by low degrees of fibrillation. Carboxymethylated NFC displayed superior tensile strength properties, lower fiber fragment content and a higher viscosity when compared to NFCEnz and NFCCMC. Interestingly, NFCEnz displayed equal or better barrier properties compared to the highly fibrillated NFCCarb.
|
|
| 75. |
- Naderi, Ali, et al.
(author)
-
A comparative study of the properties of three nanofibrillated cellulose systems that have been produced at about the same energy consumption levels in the mechanical delamination step
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 31:3, s. 364-371
-
Journal article (peer-reviewed)abstract
- The viscosity, tensile strength-and barrier properties of enzymatically pre-treated-(NFCEnz), carboxymethylated-(NFCCarb) and carboxymethyl cellulose (CMC) modified (NFCCMC) nanofibrillated cellulose systems (NFC) that have been produced at about the same energy consumption levels in the mechanical delamination step in the manufacturing of the different NFCs are reported. It was found that NFCEnz and NFCCMC are characterized by low degrees of fibrillation. Carboxymethylated NFC displayed superior tensile strength properties, lower fiber fragment content and a higher viscosity when compared to NFCEnz and NFCCMC. Interestingly, NFCEnz displayed equal or better barrier properties compared to the highly fibrillated NFCCarb.
|
|
| 76. |
- Naderi, Ali, et al.
(author)
-
A comparative study of the rheological properties of three different nanofibrillated cellulose systems
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:3, s. 354-363
-
Journal article (peer-reviewed)abstract
- The rheological properties of NFC systems in different conditions are of important for their handling and implementation in various industrial applications. In this investigation, the existence of wall-slip effects and the rheological characteristics of three different nano-fibrillated cellulose (NFC) systems - enzymatically pre-treated (NFCEnz), carboxymethyl cellulose grafted (NFCCMC) and carboxymethylated (NFCCarb) - were investigated. It was found that the rheological properties of NFCCarb are less affected by wall-slip effects when geometries with serrated surfaces are employed. The other systems showed, however, different degrees of susceptibility to these effects. The thixotropic properties of the different NFC systems, together with the impact of ambient ionic strength and temperature on the rheological properties of the systems, were also studied. It was found that the different systems displayed different rheological behaviours. In short, all systems regained most of their original properties as soon as severe shearing was ceased. The apparent viscosities of NFCEnz and NFCCMC were found to be little affected by the ionic strength of the system. However, the viscosity of the systems decreased somewhat with increasing temperatures. The viscosity of NFCCarb decreased on the other hand with the increasing ionic strength, but otherwise showed little sensitivity towards the ambient temperature. Hence, it was concluded that the rheological properties of NFCCarb were primarily governed by the electrosteric interactions between the NFC entities rather than the viscous properties of the liquid phase.
|
|
| 77. |
- Naderi, Ali, et al.
(author)
-
Can redispersible low-charged nanofibrillated cellulose be produced by the addition of carboxymethyl cellulose?
- 2015
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 30:4, s. 568-577
-
Journal article (peer-reviewed)abstract
- Carboxymethyl cellulose (CMC) was added in various amounts (< 10% (w/w)) to a lowcharged (enzymatically pre-treated) NFC, and the suspensions were blended by either a low-shear propeller mixing- or high shear homogenization protocol. The suspensions were thereafter oven-dried, and redispersed using a high shear protocol. It was found that the mixing method has a profound effect on the apparent rheology of the never-dried systems. The addition of highly charged CMC-grades enabled, already at 1% (w/w) addition, the apparent dispersion of dried NFC. The rheological responses (viscosity and storage modulus) of the neverdried NFC-CMC systems were judged as conserved, when the rheological responses of the redispersed systems were compared with those of never-dried systems that had been produced by propeller mixing. The rheological responses of the redispersed systems were on the other hand found to be lower when compared to the rheological responses of the never-dried systems that had been produced by high shearing mixing. However, the mechanical- and barrier properties of the redispersed systems were found to be inferior to the never-dried equivalents - regardless of the mixing protocol.
|
|
| 78. |
- Naderi, Ali, et al.
(author)
-
Enhancing the properties of carboxymethylated nanofibrillated cellulose by inclusion of water in the pre-treatment process
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 31:3, s. 372-378
-
Journal article (peer-reviewed)abstract
- Well-delaminated carboxymethylated nanofibrillated cellulose (NFCCarb) systems are prerequisites for many industrial applications. In this study it was shown that addition of water, in a narrow range, not only improves the efficiency of the carboxymethylation process, but also enhances the degree of delamination of NFCCarb, which leads to improved properties. The observations were proposed to be due to a more homogeneous distribution of the charged groups, brought about by the higher swelling of fibers with inclusion of water.
|
|
| 79. |
- Naderi, Ali, et al.
(author)
-
Phosphorylated nanofibrillated cellulose : production and properties
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : AB Svensk Papperstidning. - 0283-2631 .- 2000-0669. ; 31:1, s. 20-29
-
Journal article (peer-reviewed)abstract
- Phosphate functionalized nanofibrillated cellulose (NFC) was produced through an industrially attractive process, by reacting wood pulp with a phosphate containing salt, followed by mechanical delamination through microfluidization. The degrees of delamination of the phosphorylated NFCs (judged by among others AFM-imaging, rheological studies and tensile strength measurements on NFC films) were found to improve with increasing functionalization of the pulp and number of microfluidization-passes. The NFC systems were found to display similar characteristics as other well-known NFC systems. Interestingly, however, the sufficiently delaminated phosphorylated NFCs exhibited significantly lower oxygen permeability values (at RH 50%) than the published values of several well-known highly delaminated NFC systems. The potential application of the phosphorylated NFC in packaging applications can hence be envisaged.
|
|
| 80. |
- Nelsson, Erik, et al.
(author)
-
Low dosage sulfite pretreatment at different refining temperatures in mill scale TMP production
- 2017
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:1, s. 59-69
-
Journal article (peer-reviewed)abstract
- The effects of low dosage sodium sulfite ( Na2SO3) pretreatment (0, 0.6 and 1.2% on bone dry wood, pH 9) at two different refining temperatures (4.6 and 6.4 bar(g) refiner housing pressure) were evaluated for production of thermomechanical pulp with a double disc refiner in mill scale using Norway spruce wood at Braviken paper mill (Holmen Paper AB, Sweden). The sulfonate content of the pulps was not affected by the different refining temperatures and was 0.29% (as Na2SO3 equivalents) for the highest sulfite addition.Tensile index at constant SEC was increased by 3.2 Nm/g when the refining temperature was increased, and by 8.6 Nm/g when 1.2% sodium sulfite was added. The effects were additive and led to an increase in tensile index of similar to 12 Nm/g at constant SEC when combined and would enable a reduction in SEC of 380 kWh/bdt (similar to 20%) to similar tensile index. The degree of delamination and internal fibrillation of the fibers was increased by both increased refining temperature and sulfite addition.Pulp brightness was slightly reduced (<= 0.4% ISO) by increased refining temperature and increased (2-3% ISO), when sodium sulfite was added. Spectra of reflectance factors (360-740 nm) were used to study the optical properties of produced pulps.
|
|
| 81. |
- Nelsson, Erik, 1983-, et al.
(author)
-
Low dosage sulfite pretreatment in a modern TMP-line
- 2015
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 30:4, s. 591-598
-
Journal article (peer-reviewed)abstract
- The effects of low dosage sulfite pretreatment combined with modern high consistency double disc refining were evaluated for production of thermomechanical pulp in a mill scale trial using Norway spruce wood at the Braviken paper mill (Holmen Paper AB, Sweden). Spruce wood chips were mechanically pretreated in an Impressafiner before impregnation with different dosages (0-1.2%) of sodium sulfite (Na2SO3) at pH 9. Approximately 23% of the added sulfite was converted to sulfonate groups in pulp, resulting in a sulfonate content of 0-0.28% (as Na2SO3). The low dosage sulfite addition increased tensile index, elongation, density, brightness and decreased shive content, light scattering and light absorption coefficients when compared at equal specific energy consumption (SEC). The increase in tensile index was proportional to dosage of sulfite. Further analyses showed that low dosage sulfite addition did not affect the distribution of the Bauer-McNett fractions nor the fibre length for pulps refined with equal SEC. However, the low dosage sulfite addition increased fibre delamination/internal fibrillation (D/IF). With the addition of 1.2% Na2SO3, it was possible to produce pulp with a tensile index of 47 Nm/g using ~320 kWh/bdt (~15%) lower refining energy, compared with pulps produced without sulfite addition.
|
|
| 82. |
- Nilsson, Lars, 1966-, et al.
(author)
-
Predicting water removal during vacuum dewatering from fundamental fibre property data
- 2015
-
In: Nordic Pulp & Paper Research Journal. - Härnösand : Mittuniversitetet. - 0283-2631 .- 2000-0669. ; 30:2, s. 265-271
-
Journal article (peer-reviewed)abstract
- Control of the solids content after vacuum dewatering is vital for efficient control and energy use of the paper machine. Dewatering is a complex function of many parameters such as fibre and pulp properties as well as settings on the paper machine and a predictive model for dewatering will require extensive and detailed studies of the occurring physical phenomena. The hypothesis investigated in the present study is that fibre width and fibre length density measured for fibres suspended in water can be used for estimating the achievable dryness in vacuum dewatering. The hypothesis was tested by comparing model predictions to experimental data for 11 different pulps. The results show that the dryness after vacuum dewatering can be estimated from the fibre length density and the fibre width for the fresh pulps using an elliptical fibre cross-section model with a ratio of 0.48 between the short and long axes. For the dried pulps a lower value was needed to reach a good agreement.
|
|
| 83. |
- Nilsson, Lars, 1966-, et al.
(author)
-
The influence of grammage and pulp type on through air drying
- 2015
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 30:4, s. 651-659
-
Journal article (peer-reviewed)abstract
- The influence of grammage and pulp type on through air drying was studied. The temperature of a sample was measured during the drying process and the observed temperature changes were used to evaluate the drying process. Laboratory sheets with grammages 15- 60 g/m², from two softwood and two hardwood bleached chemical pulps were used. All samples were analysed with respect to formation, flow resistance, modified permeability, mean drying time, non-uniformity of drying time, and area- and mass-specific drying rate. The pulps had different modified permeabilities but showed similar behaviour when analysed as a function of grammage. A constant value was found for higher grammages, while an increase in modified permeability was found at decreasingly low grammages. Almost all pulp and grammage combinations had similar area-specific drying rates, but the mass-specific drying rates decreased with grammage. However, the samples with lower grammages had mass specific drying rates independent of modified permeability, where samples with increasing grammage showed an increasing dependency. This implies that the drying efficiency at low grammages was not controlled by the volume flow of the drying air. A good correlation was found between energy needed to evaporate water and energy supplied by the drying air as estimated from the surface temperature and air flow measurement. The surface temperature can therefore be used to quantify the drying process.
|
|
| 84. |
- Nordström, Bengt, et al.
(author)
-
Effect of fiber length on formation and strength efficiency in twin-wire roll forming
- 2017
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:1, s. 119-125
-
Journal article (peer-reviewed)abstract
- A change in fiber length is known to change fiber flocculation and formation of machine-made paper, but it has been unclear how a change in formation through fiber length affects strength efficiency. (The strength efficiency reflects how well the furnish strength, as indicated by the handsheet strength, is utilized in the machine-made paper.) The effect of fiber length on strength efficiency in twin-wire roll forming was presently investigated by examining two furnishes with different average fiber length, prepared from the same batch of softwood kraft pulp, over a wide range of headbox consistencies on a pilot machine. An increase in fiber length resulted not only in worse Ambertec formation over the whole range of headbox consistencies but also in faster relative deterioration of the formation with increasing consistency. Tensile strength efficiency and Z-strength efficiency were both reduced when the formation was impaired through increased fiber length, and the effect was similar to the effect of a corresponding change in formation through headbox consistency. A given change in formation, through fiber length or headbox consistency, had a larger relative effect on Z-strength efficiency than on tensile strength efficiency.
|
|
| 85. |
- Nordström, Bengt, et al.
(author)
-
Effect of machine speed on formation and strength efficiency in twin-wire roll forming of never-dried unbleached softwood kraft pulp
- 2018
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:2, s. 271-278
-
Journal article (peer-reviewed)abstract
- There is a constant drive to increase machine speed in the production of kraftliner and most other major paper grades, but the separate effect of the machine speed on the paper properties has been unclear. The effect of machine speed in twin-wire roll forming of never-dried unbleached softwood kraft pulp was evaluated here in a pilot machine investigation by examining three machine speed levels (500, 750, and 1000 m/min) over a series of jet-to-wire speed differences. Similar headbox consistency and draw from wire section to winding were employed at the different machine speed levels. An increase in the machine speed had a favorable effect on formation and Z-strength efficiency over a wide range of jet-to-wire speed differences, whereas the machine speed had an insignificant effect on tensile strength efficiency and tensile stiffness efficiency. For all properties, the overall shape of the jet-to-wire speed difference curve remained similar when changing the machine speed.
|
|
| 86. |
- Nordström, Bengt, et al.
(author)
-
Effect of refining on strength efficiency in twin-wire roll forming of never-dried unbleached softwood kraft pulp
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:4, s. 624-633
-
Journal article (peer-reviewed)abstract
- Whereas refining is required for the strength development of chemical pulps, it has been unclear how refining affects the utilization of the furnish strength, as reflected by the handsheet strength, in the machine-made paper (strength efficiency). This work examined effects of refining on formation and strength efficiency in twin-wire roll forming of never-dried unbleached softwood kraft pulp in a pilot machine investigation comprising three separate sections. The first section showed that a change in refining energy has no significant effect on formation, tensile strength efficiency, tensile stiffness efficiency, or compression strength efficiency at a given consistency when the fiber length remains similar. The second section demonstrated that a change in kappa number has no significant effect on formation or tensile strength efficiency at a given consistency when the fiber length of the refined pulp remains similar. Here, an increase in kappa number involved an increase in refining energy. The third section showed that a reduction in headbox consistency results in an improvement in formation and tensile strength efficiency that is similar in magnitude over the whole refining curve.
|
|
| 87. |
- Nordström, Bengt, et al.
(author)
-
Effect of softwood kraft fiber coarseness on formation and strength efficiency in twin-wire roll forming
- 2018
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:2, s. 237-245
-
Journal article (peer-reviewed)abstract
- It has been unclear how fiber coarseness affect formation and the utilization of furnish strength in the machine-made paper (strength efficiency). In this work, the effect of softwood kraft fiber coarseness on formation and strength efficiency in twin-wire roll forming was examined in a pilot machine investigation. A reduction in softwood kraft fiber coarseness from 0.21 to 0.17 mg/m, associated with a reduction in fiber grammage from 6.2 to 5.2 g/m2, was found to have no significant effect on formation at the point of minimum shear during dewatering. The insignificant effect of reduced coarseness can be interpreted as the net result of two effects, namely, an increase in the number of fiber layers at a given grammage (favorable) and an increase in the flocculation tendency (unfavorable). While the effect of coarseness was negligible at the point of minimum shear, coarser fibers enabled larger improvement in formation through the jet-to-wire speed difference. In correspondence to the insignificant effect on formation, fiber coarseness had a negligible effect on tensile strength efficiency and Z-strength at the point of minimum shear. The larger improvement in formation through the jet-to-wire speed difference for the coarser fibers was reflected in a favorable effect on Z-strength efficiency.
|
|
| 88. |
- Nordström, Bengt, et al.
(author)
-
Effect of the ratio of softwood kraft pulp to recycled pulp on formation and strength efficiency in twin-wire roll forming
- 2017
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:2, s. 229-236
-
Journal article (peer-reviewed)abstract
- Research has been undertaken to investigate how the tensile strength efficiency and Z-strength efficiency in twin-wire roll forming is affected when changing formation through the softwood kraft content in a mixture with recycled pulp. The effect of a change in formation through the softwood kraft content and the effect of a change in formation through headbox consistency were also compared. Five kraft contents (0, 25, 50, 75 and 100%) were investigated at volumetric headbox flow rates of 111 and 1,77l/sm. Three additional flow rates were used at a kraft content of 50%. Impaired formation through the softwood kraft content reduced tensile strength efficiency and Z-strength efficiency. Both these properties were similarly affected whether the formation was changed by the softwood kraft content or the headbox consistency. The relative impact of formation was larger for Z-strength efficiency compared with tensile strength efficiency. The reduction in tensile strength efficiency was replicated in a smaller relative increase in tensile strength for machine-made paper than for handsheets made of the furnish. Considering the effect on strength efficiency when evaluating furnishes has been demonstrated as an important concern.
|
|
| 89. |
- Nordström, Bengt, et al.
(author)
-
One-sided versus two-sided roll forming of never-dried softwood kraft pulp : effects on formation and strength efficiency
- 2017
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:3, s. 407-414
-
Journal article (peer-reviewed)abstract
- Research has been undertaken to demonstrate the effect on z-strength of headbox consistency in one-sided versus two-sided roll forming of unbleached softwood kraft pulp over a wide range of jet to wire speed differences. In addition, formation and tensile strength were evaluated. Using a pilot machine, each forming method was examined at two headbox consistency levels (0.4 and 0.6%). The wire speed was varied from 550 to 660m/min while maintaining the headbox conditions, resulting in a change in grammage from approximately 71gsm to 61gsm. A significantly higher Z-strength was noted for one-sided roll forming at a headbox consistency of 0.4% compared with two-sided roll forming. However, an increase in consistency resulted in a ore similar Z-strength through a larger reduction in Z-strength efficiency for one-sided than two-sided roll forming. In addition, Z-strength was promoted by formation improvement through the jet to wire speed difference in both one-sided and two-sided roll forming of the furnish. The effects of the jet to wire speed difference on formation and tensile strength efficiency in one-sided roll forming of the present furnish were relatively more favourable and more similar to the effects in two-sided roll forming.
|
|
| 90. |
- Nordström, Bengt, et al.
(author)
-
Successive twin-wire roll forming of two-ply paper with softwood kraft pulp and recycled pulp - Effect of kraftply formation on Z-strength
- 2017
-
In: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 32:4, s. 639-645
-
Journal article (peer-reviewed)abstract
- Kraftliner and kraft-top liner typically consists of two or more plies that are formed separately and combined by couching. The Z-strength tends to be limited by the ply adhesion, and the softwood kraft pulp used is commonly refined beyond the optimum for tensile strength to ensure sufficient Z-strength. In this work, two-ply forming by successive twin-wire roll forming, was evaluated with moderately refined never-dried unbleached softwood kraft pulp and recycled pulp in different plies. Successive twin-wire roll forming involved two-sided roll forming of the first ply and onesided roll forming of the second ply directly onto the first ply. Two-sided roll forming of the recycled pulp and onesided roll forming of the kraft pulp was evaluated in parallel to the reversed combination. The Z-strength was found to be limited by the strength of the kraft ply rather than by the ply adhesion. The effect on Z-strength when changing headbox consistency or when going from one-sided to two-sided roll forming for the kraft ply was in agreement with results for single-ply forming. Besides the favorable findings for Z-strength, the results suggest that successive roll forming enables an efficient utilization of the tensile strength potential of the softwood kraft pulp.
|
|
| 91. |
- Norgren, Sven, 1973-, et al.
(author)
-
Strong paper from spruce CTMP - Part II : Effect of pressing at nip press temperatures above the lignin softening temperature
- 2018
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:1, s. 142-149
-
Journal article (peer-reviewed)abstract
- The main objective of the current study was to demonstrate that it is possible to enhance strength properties of sheets from spruce HT-CTMP and CTMP furnishes up to the same level as is common on sheets from softwood kraft pulps by changing conditions in papermaking. To achieve that, sheets of spruce HT-CTMP and CTMP were consolidated at densities close to that of the reference bleach kraft pulp by pressing at press nip temperatures well above the tack and softening temperatures of lignin. On sheets from spruce CTMP (CSF 420 ml), where the fibers were surface treated with cationic starch, it was possible to reach tensile index at the same level as on sheets from the untreated reference kraft pulp. The compression strength (SCT) of CTMP and HT-CTMP sheets, which were achieved at the highest press nip temperature (200 °C) in the study, was equal to or higher than that of the reference kraft pulp sheets. The results show that there is a great yet unexploited potential in papermaking from spruce HT-CTMP and CTMP furnishes, which could be utilized in manufacturing of products where very high requirements upon strength is demanded.
|
|
| 92. |
- Nyflött, Åsa, 1986-, et al.
(author)
-
Influence of kaolin addition on the dynamics of oxygen mass transport in polyvinyl alcohol dispersion coatings
- 2015
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 30:3, s. 385-392
-
Journal article (peer-reviewed)abstract
- The permeability of dispersion barriers produced from polyvinyl alcohol (PVOH) and kaolin clay blends coated onto polymeric supports has been studied by employing two different measurement methods: the oxygen transmission rate (OTR) and the ambient oxygen ingress rate (AOIR). Coatings with different thicknesses and kaolin contents were studied. Structural information of the dispersion-barrier coatings was obtained by Fourier transform infrared spectroscopy (FTIR) spectroscopy and scanning electron microscopy (SEM). These results showed that the kaolin content influences both the orientation of the kaolin and the degree of crystallinity of the PVOH coating. Increased kaolin content increased the alignment of the kaolin platelets to the basal plane of the coating. Higher kaolin content was accompanied by higher degree of crystallinity of the PVOH. The barrier thickness proved to be less important in the early stages of the mass transport process, whereas it had a significant influence on the steady-state permeability. The results from this study demonstrate the need for better understanding of how permeability is influenced by (chemical and physical) structure.
|
|
| 93. |
- Nygårds, Mikael, et al.
(author)
-
Comparison and analysis of in-plane compression and bending failure in paperboard
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:3, s. 432-440
-
Journal article (peer-reviewed)abstract
- In-plane compression of paperboard, using long (LCT) and short compression test (SCT), and bend-ing, using the L&W creasability tester, have been ana-lyzed using three paperboards with similar strength prop-erties but different ZD profiles. The failure loads from the methods have been compared and the failure mechanisms analyzed. It was shown that at maximum bending moment from bending of samples using L=10 mm and L=50 mm, the SCT value and the maximum bending force from LCT all varied linearly with each other, indicating that same dam-age mechanism is activated. It was suggested that delamination cracks were initiated during SCT and LCT as well as during bending when plastic deformation had been initiated in an outer ply subjected to compressive stress. The plastic deformation would be initiated when the yield stress in the ply was reached, determined by an in-plane tensile test. When plastic deformation takes place, it will generate shear induced delamination cracks in locations with low shear strengths, e.g. in the interfaces or within the middle ply. The location depends on the material design strategy used in manufacturing the paper quality. To control the in-plane compression properties in pa-perboard one should control the yield stress (or possibly the failure stress) of the outer plies. Increased stress gives higher in-plane compression strength. Moreover, the interfaces strength is important, since increased interface strength (or lack of interfaces) prevents delamination.
|
|
| 94. |
- Nyström, Jonas, et al.
(author)
-
An experimental study of the chipping process with focus on energy consumption and chipping angles
- 2018
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:3, s. 460-467
-
Journal article (peer-reviewed)abstract
- A series of chipping experiments were performed under both dynamic and quasi-static conditions in a laboratory wood chipper (dynamic) and in a MTS-servohydraulic testing machine (quasi-static). One aim with the experiments was to investigate the rate dependency of the energy consumption during chipping. Another aim was to try to determine the load per unit knife edge length required to initiate cutting. The experiments were carried out using different combinations of spout and edge angles. It was found that for large edge angles (keeping the spout angle constant at 30°) there was a slight rate dependency such that the energy consumption was larger at higher cutting rates which is quite in opposite of what is expected if wood is assumed to be a viscoelastic material. It was also found that to determine the force at initiation of cutting, is not a trivial task. Both Acoustic Emission monitoring and visual inspection was used to this end. The wood species used in this study was pine (Pinus silvestris).
|
|
| 95. |
- Oko, Asaf, et al.
(author)
-
Measurements and dimensional scaling of spontaneous imbibition of inkjet droplets on paper
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : SPCI. - 0283-2631 .- 2000-0669. ; 31:1, s. 156-169
-
Journal article (peer-reviewed)abstract
- We investigate theoretically and experimentally the spontaneous imbibition of water based inkjet formulations utilizing paper capillary rise and imbibition of inkjet drops. We approximate the paper structure to a two dimensional anisotropic porous material, and using Darcy's law as a base, we derive dimensionless groups that scale drop imbibition. This derivation is based on a previous dimensional scaling of drop imbibition on thick isotropic porous material. We apply this scaling to a paper substrate by measuring the average drop imbibition rate, and perform paper capillary rise experiments to obtain the average system parameters required for the scaling. The results suggest that this approach is a valuable tool to predict drop imbibition rates on paper. We then continue and perform the same sets of experiments on a different paper with similar structure that is surface treated (surface sized) with CaCl2 salt, an additive that is known to improve print quality. We find that due to rapid aggregation of the colorant ink by the CaCl2, the imbibition rate is slowed down in the capillary rise experiments, i.e., on much larger scales compared to a single inkjet drop. However, the presence of CaCl2 has only minor effect over the average imbibition rates of single drops. Imbibition rates on the CaCl2 surface sized paper did not give adequate scaling as a result of the fact that the aggregation was not included the theoretical assumptions behind the scaling.
|
|
| 96. |
- Osterberg, Monika, et al.
(author)
-
Editorial : From understanding the biological function of lignin in plants to production of colloidal lignin particles
- 2017
-
In: Nordic Pulp & Paper Research Journal. - : AB Svensk papperstidning. - 0283-2631 .- 2000-0669. ; 32:4, s. 483-484
-
Journal article (peer-reviewed)abstract
- There is a paradigm shift going on in lignin utilization. High-volume materials and chemicals, as well as more engineered materials, like carbon fibers or active carriers, are currently being developed. However, in order to enhance lignin utilization in these and other value-added products, there is a need for better understanding of lignin function in woody tissues plus control over isolation, fractionation and other processing technology. Therefore, part of this issue is dedicated to articles about lignin. These range from lignin extraction to scale-up of the colloidal lignin particle production process. Focus is on fundamental understanding of interactions, a necessity for successful applications of this complex biopolymer.
|
|
| 97. |
- Ottesen, Vegar, et al.
(author)
-
Mixing of cellulose nanofibrils and individual furnish components : Effects on paper properties and structure
- 2016
-
In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:3, s. 441-447
-
Journal article (peer-reviewed)abstract
- Thermo-mechanical pulp (TMP) handsheets with different fractions of cellulose nano fibrils (CNF) and ground calcium carbonate (GCC) were made. CNF and retention chemicals were added in three different ways; to GCC, to long fibre fraction (LFF) or to complete furnish. The different addition strategies affected dewatering time, tensile strength and permeability, however opacity was not affected. Depending on filler and CNF levels, adding CNF to GCC produced the most beneficial effects on paper properties; CNF had a lower impact on dewatering times and permeability and GCC reduced strength less than for competing strategies. Adding CNF to LFF produced the least beneficial results using the same metrics. Scanning electron microscopy (SEM) analysis of the sheets reveal that sheets produced using the different strategies are structurally different; adding CNF and retention chemicals to GCC appears to have increased GCC clustering, whereas adding CNF and retention chemicals to LFF appears to have increased the fraction of GCC adsorbed on the fiber walls. CNF and retention chemical addition to complete furnish showed GCC clustering and adhering to the fiber walls, of which clustering appeared the most common.
|
|
| 98. |
- Ottesen, Vegar, et al.
(author)
-
Viability and properties of roll-to-roll coating of cellulose nanofibrils on recycled paperboard
- 2017
-
In: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 32:2, s. 179-188
-
Journal article (peer-reviewed)abstract
- Cellulose nanofibrils (CNF) are, due in large part to excellent gas barrier properties, a potential environmentally friendly alternative to inorganic and petrochemical coatings of e.g. paperboard in packaging applications. In the current paper successful roll-to-roll coating of three qualities of CNF is demonstrated on a recycled quality, porous paperboard using a custom-built pilot machine. Single layers of three different thicknesses were applied for each coating. The three CNF qualities used were carboxymethylated CNF (CNF-C), TEMPOoxidized CNF (CNF-T) and mechanically produced CNF without chemical pre-treatment (CNF-M). All three qualities, which have a range of surface charge, fibril size and fibril size distribution, are shown to produce films that adhere well to the base board. It is revealed that the coating is suspended across surface pores in the base board, as opposed to penetrate into the base board pore structure. Samples were investigated for air and water permeability, gloss, surface roughness and hole density in the coating. Chemically pretreated qualities outperform CNF-M. Addition of 5 wt% carboxy-methyl cellulose (CMC) was shown to reduce hole formation, improve gloss and reduce surface roughness. For thick applications of pre-treated CNF, in particular CNF-C, mechanical strength of the board in and out of the plane increase beyond the un-treated or water treated base board. Possibly a consequence of matter migrating through the base board from the CNF suspension.
|
|
| 99. |
- Ovaskainen, Louise, et al.
(author)
-
The effect of different wear on superhydrophobic wax coatings
- 2017
-
In: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 32:2, s. 195-203
-
Journal article (peer-reviewed)abstract
- Wear resistance of superhydrophobic coatings made by spraying a crystallizing wax from supercritical carbon dioxide solutions was evaluated using several methods. Scratch tests were performed using a tip in contact with the surface using atomic force microscope (AFM). Compression tests were performed by applying different loads on a rubber stamp placed on the surface. Frictional wear was evaluated by stroking an index finger over the surfaces while measuring applied load and friction. The wetting properties of the coatings were subsequently evaluated as advancing and receding water contact angles, superhydrophobic sliding resistance according to a recently developed method and surface roughness, coating morphology was studied using scanning electron microscopy and optical profilometry. Scratching with tip of an AFM cantilever with a force of 12 nN removed major fraction of the wax coating from underlying silica substrate whereas subjecting the surfaces to a compressive load up to 59 kPa did not significantly influence the superhydrophobicity of the coatings. Frictional wear measurements indicate that superhydrophobic properties were immediately lost after pressing and moving a finger over the coating, as movement of the finger destroyed the fine surface structure. Nevertheless, the surfaces could withstand up to 200000 falling water drops without losing their superhydrophobicity. © 2017 De Gruyter Open Ltd. All rights reserved.
|
|
| 100. |
- Pettersson, Gunilla, et al.
(author)
-
Strong and bulky paperboard sheets from surface modified CTMP, manufactured at low energy
- 2015
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 30:2, s. 318-324
-
Journal article (peer-reviewed)abstract
- A description is given regarding methods used to manufacture strong and bulky sheets from furnishes based on a broad range of surface modified CTMP qualities. Starch and CMC are adsorbed on the fibre surfaces using a multilayer or a MIX concept. It is shown that both the in-plane and out-of-plane strength for the CTMP based sheets after such surface treatment can be more than doubled at a maintained density. This can be utilized to improve bending stiffness or to reduce the basis weight in multi-ply paperboards.
|
|
