| 1. |
- Ahlbom, Anders, 1993, et al.
(author)
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Using guaiacol as a capping agent in the hydrothermal depolymerisation of kraft lignin
- 2023
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In: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 38:4, s. 619-631
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Journal article (peer-reviewed)abstract
- The depolymerisation of softwood kraft lignin was investigated, under hydrothermal conditions at 290 °C and 250 bar, with guaiacol in the reactor feed to evaluate its impact on the formation of char and on the molecular weights of the products. The effect of residence time was investigated in the time span 1-12 min. Lignin is depolymerised during the process and guaiacol is both formed and consumed during the reaction, with clearly noticeable changes as early as in the first minute of reaction. Although the addition of guaiacol in the reactor feed causes a reduction in the weight average molecular weight of the products, the yield of char increases. Longer residence times result in repolymerisation of the reaction products as well as a further increase in the yield of monoaromatic components and char.
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| 2. |
- Al-Dajani, W. W., et al.
(author)
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On the isolation and structure of softwood residual lignins
- 2002
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In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 17:2, s. 193-198
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Journal article (peer-reviewed)abstract
- Different softwood residual lignins were isolated by acid hydrolysis of kraft and soda Pulps. Complete isolation of lignin Could not be achieved in one hydrolysis step. The yield of lignin varied between 35 and 55%. A more acidic, second hydrolysis step was therefore necessary to isolate almost all the lignin remaining in the Pulp residue, giving a total lipin yield of 91%. Alkaline extraction of the pulp was almost as efficient as acid hydrolysis in isolating residual lignins. However, alkaline extraction gave less pure lignin fractions and there was a clear indication of the existence of lignin-carbohydrate bonds. Pine wood meal was acid-hydrolyzed in the same way as the pulps. After two-stage acid hydrolysis, the combined lignin yield was only 45% of the Klason lignin content, which means that native lignin is more difficult to isolate front wood than residual lignin front a chemical pulp. It is Concluded that the difficulty encountered in isolating residual lignin by acid hydrolysis is a problem of limited accessibility due to a complex carbohydrate network surrounding the lignin.
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| 3. |
- Alam, Anzar, et al.
(author)
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Online surface roughness characterization of paper and paperboard using a line of light triangulation technique
- 2012
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:3, s. 662-670
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Journal article (peer-reviewed)abstract
- Within both the paper and paperboard industries, real time monitoring and measurement of surface roughness of a paper moving at high velocities is an important and challenging area of research. The uniform surface, for an entire production, can be effectively achieved by monitoring and controlling the paper surface roughness, in real time during the manufacturing steps. Presently the majority of paper industries rely on traditional laboratory profilometers. The obvious limitations of lab profilometers are that these are slow, do not measure the quality of entire reels but rather deal with only a few small pieces of samples taken from the end of the reels and it is difficult to make any possible correction in the productionlines without knowing the online roughness data. To eradicate the disadvantages associated with conventional measurements, an online prototype instrument has been developed that measures the surface roughness during the manufacturing steps, and is based on a line of lighttriangulation technique. The prototype technique will be of assistance in ensuring tight process control in order to maintain both a better and auniform quality throughout the entire production. It measures the whole reel, meter by meter, in traditional units of roughness and is also capable of characterizing the topography in a wide range of wavelength spectra. The article presents the online analyses results obtained from the developed prototype. The real time measurements, in a paperboard pilot mill, have successfully characterized and distinguished 16 different grades of newspaper and paperboard reels including reels which have the same family of quality grades and materials.
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| 4. |
- Alam, Mohammad Anzar, et al.
(author)
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Investigation of the surface topographical differences between the Cross Direction and the Machine Direction for newspaper and paperboard
- 2011
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 26:4, s. 468-475
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Journal article (peer-reviewed)abstract
- Paper and paperboard surface quality is constantly being improved by the industry. This improvement work deals with the essential fact that the surface topography must be measured, both in relation to offline and online measurements for the manufactured products. Most measurements relating to surface topography (especially online) are performed either in the machine direction (MD) or in the cross direction (CD). It has been the opinion of SCA Ortviken AB and Iggesund Paperboard AB that the surface topography amplitudes are almost always higher in the CD than in the MD, for their products which consist of newspaper and paperboard. This article aims to investigate the rela-tionship between the CD and the MD surface topography amplitudes for a wide range of spatial wavelength for both newspaper and paperboard. The tests and investiga-tions have been conducted using an FRT Microprof profilometer within the range 20 μm up to 8 mm, and the results confirm that the surface topography amplitudes are higher in the CD for most of the shorter spatial wavelength within this range. The results also show significant differences between measurements for different paper qualities, suggesting a requirement to investigate the relationship between the CD and the MD topography for all paper and paperboard qualities of interest for a paper or paperboard mill, before a decision is made in relation to a measurement method.
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| 5. |
- Aldaeus, Fredrik, et al.
(author)
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Miniaturized determination of ash content in kraft lignin samples using oxidative thermogravimetric analysis
- 2017
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:2, s. 280-282
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Journal article (peer-reviewed)abstract
- A study has been made of several aspects of determination of ash content in kraft lignin samples using thermogravimetric analysis (TGA). Three different methods were used; with the main differences between the methods being that two have a temperature hold at 250 deg C to remove volatiles and that the three methods use different maximum temperatures, namely 525, 550 and 575 deg C, respectively. The three kraft lignins used were produced using the LignoBoost lignin isolation process. It has been demonstrated that the results obtained by the different temperature programmes showed no significant difference. The results were comparable with those from using oven ignition. Moreover, the limit of quantification was several orders of magnitude lower than when using oven ignition. It has been recommended that if TGA is used for determination of ash content, a temperature programme from a standard method should be used, which should be mentioned together with the results. The temperature programme in method one (corresponding to ISO 1762) was the shortest and the preferable method. A well as requiring less labour due to fewer movements in the analytical protocol, the TGA methods enabled a high sample throughput due to autosampling possibilities.
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| 6. |
- Alfthan, Johan
(author)
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Experimental study of non-linear stress relaxation and creep of paper materials and the relation between the two types of experiments
- 2010
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 25:3, s. 351-357
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Journal article (peer-reviewed)abstract
- The non-linear time-dependent mechanical behaviour of three different commercial paper grades was investigated. Stress relaxation and creep tests were carried out in MD and CD using different load levels. The strain in each test was split in a linear part and a non-linear part. From the stress and the linear part of the strain in the test, a stress relaxation modulus or a creep compliance was calculated. The stress relaxation moduli and creep compliances determined in this way were observed to be independent of the load level. The stress relaxation moduli and creep compliances for each paper were further independent of the loading direction (MD/CD) when scaled by the elastic modulus. It was also shown that the stress relaxation modulus was approximately equal to the inverse of the creep compliance, which is what would have been expected if linear viscoelastic theory had been applicable.
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| 7. |
- Ali, Silvia, et al.
(author)
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From wood shavings to mechanical pulp - a new raw material?
- 2005
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 20:4, s. 418-422
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Journal article (peer-reviewed)abstract
- Wood chips used in the thermomechanical pulping (TMP) process were originally designed to suit the chemical pulping process. The production of small wood pieces more suitable for the TMP process could lead to an energy saving in this energy-intensive process. This paper discusses the potential benefits of using wood shavings instead of chips as the raw material for TMP production. In some exploratory trials, wood shavings with a thickness of about 2 mm and wood chips were refined in two steps under normal TMP process conditions in a pilot refiner. The first-stage refining was performed under pressurized conditions at 130°C. The second-stage refining was performed at atmospheric pressure at approximately 100°C at four different energy levels. The quality of the pulp produced from wood shavings was found to be better than that of the pulp produced from wood chips, with respect to both strength properties (except tear index) and optical properties at comparable energy levels. The potential for energy savings at a given tensile index using wood shavings instead of the traditional chips is estimated to be about 25%.
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| 8. |
- Alm, Hajer Kamal, et al.
(author)
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Effect of excess dispersant on surface properties and liquid interactions on calcium carbonate containing coatings
- 2010
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 25:1, s. 82-92
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Journal article (peer-reviewed)abstract
- The aim of this work was to identify what effects excess amount of sodium polyacrylate, a commonly used dispersant, has on the coating properties and the interaction between ink and the paper coating in offset printing. Since polyacrylate strongly interacts with calcium ions, soluble calcium salt was added to some coating colours to illustrate the impact of charge neutralization by calcium ions. It was found that the coating structure was only slightly affected by the extra addition of polyacrylate, showing some weak flocculation, whereas the surface chemistry was strongly influenced. The coatings became more polar and interacted more strongly with water. This resulted in slower ink setting and reduced ink-paper coating adhesion, especially in the presence of applied water/dampening solution, which are identified as contributory factors in ink piling and print mottle.
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| 9. |
- Andersson, Christian, et al.
(author)
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Evaluation of the stress-strain properties in the thickness direction : Particularly for thin and strong papers
- 2012
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 287-294
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Journal article (peer-reviewed)abstract
- The performance of the paper in a number of converting operations such as creasing, bending, printing, and plastic coating put great demands on the mechanical properties in the thickness direction of the material. The knowledge of strength, elastic- and plastic behavior in tension and compression in the thickness direction is needed for a comprehensive description of the performance of the material in these operations. In spite of its importance, very few publications deal with the evaluation of the entire tensile stress-strain curve of paper in the thickness direction. A likely reason for this is the intrinsic difficulty of testing a thin, uneven, porous, fibrous and compressible material such as paper with sufficient precision and testing time efficiency. The z-directional strength test is usually performed by fastening the paper by means of double-adhesive tape to metal platens. The platens are fastened in a testing machine and strained to break. The adhesion of the tape is the limiting factors for how strong papers that can be tested. The tape-based method also is expected to have a lower limit in grammage due to the penetration of the adhesive. The aim of the present publication was to show a procedure how to evaluate the entire stress-elongation curve in the z-direction of papers, using a lamination method for fastening the paper to the metal platens. From this curve the z-strength, z-modulus, z-strain at break, zenergy at break and z-fracture energy could be extracted. Such information is, so far, non-existing in the literature.
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| 10. |
- Andersson, Henrik, et al.
(author)
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Contacting paper-based supercapacitors to printed electronics on paper substrates
- 2012
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 476-480
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Journal article (peer-reviewed)abstract
- Hybrid printed electronics, in which printed structures and silicon-based components co-exist will likely be among the first commercial solutions. In this case the paper substrate acts much in the same way as circuit boards, containing conductive tracks and acting as a carrier for the electrical components. It is important to consider the contacting of the components to be able to produce low resistance electrical contacts to the conductive tracks. Supercapacitors are able to deliver a large amount of current in a short time and are a good option for short term energy storage and if the printed product is to be used only one, or a few times, it can be the only power source needed. When manufacturing printed electronics, the overall resistance of the printed tracks as well as the contact resistance of the mounted components will add up to the total resistance of the system. A high resistance will cause a voltage drop from the power source to the component. This will waste power that goes to Joule heating and also the voltage and current available to components may be too low to drive them. If the intention is to use a power supply such as batteries or solar cells this becomes a limitation. In this article have been tested several conductive adhesives used to contact paper based supercapacitors to ink jet printed silver tracks on paper. The best adhesive gives about 0.3 Ω per contact, a factor 17 better compared to the worst which gave 5 Ω. The peak power that is possible to take out from a printed system with a flexible battery and super capacitors is about 10 times higher than compared with the same system with only the battery.
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