| 1. |
- Hyll, Kari, et al.
(författare)
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Comparison of optical instruments for fines and filler characterisation
- 2017
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Ingår i: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 32:1, s. 97-109
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Tidskriftsartikel (refereegranskat)abstract
- A laser diffractometer and three image-based instruments with spatial resolutions between 0.33 and 10 mu m/pixel were compared through measurements on calibration spheres and fine fractions comprising pulp fines of various types, neat PCC filler, and a mixture of fines and fillers. The laser diffractometer was highly sensitive to the keyed in refractive index of the samples, which was calculated based on volume-based mixing rules. A high-resolution flow cytometer and a high-resolution fibre analyser were found to be complimentary for measurements on neat fines and fines/filler mixtures, and superior to the laser diffractometer. When measuring on fillers, the laser diffractometer performed as well as the high-resolution flow cytometer, which was capable of resolving single filler particles. The sizes of the calibration spheres were overestimated by the image-based instruments, and the measurement uncertainty was high. The uncertainty was mainly attributed to the unrestricted particle motion, and the low accuracy to the dissimilar optical properties of the calibration material, compared to fines. Thus, calibration materials with shape and optical properties more similar to fines should be developed.
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| 2. |
- Kari, Hyll, 1984-, et al.
(författare)
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Optical methods for fines and filler size characterization : Evaluation and comparison
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The pulp fines and mineral fillers in the fine fraction of a papermaking stock influence process conditions and sheet properties. The influence is largely dependent on the size and shape of the particles. Quantitative characterization of the size and shape of fines and fillers would aid in process control and prediction of product properties. Thus, the aim of the study was to evaluate and compare optical instruments which can be used to quantitatively characterize the fine fraction of a papermaking stock. The compared instruments were the Mastersizer2000 from Malvern, based on diffraction scattering of a laser beam, the ImageStream from Amnis, and the Fiber Tester and Fiber Tester Plus from ABB Lorentzen & Wettre. The last three instruments are all based on imaging of the particles and have spatial resolutions ranging from 0.33 µm to about 10 µm per pixel.All instruments overestimated the size of calibration spheres with known sizes. In several cases, calibration particles that were smaller than the spatial resolution of the instrument were detected. In these cases, the relative measurement error was large, likely due to positioning and quantization errors. It is also suggested that the oversizing was partly due to dissimilar optical properties of the calibration particles, compared to the typical sample, and that better calibration materials for fines need to be developed.For the image-based instruments, the relative share of fines and filler particles increased with as the size of the measured particles decreased. Thus, with higher spatial resolution, more particles were detected. However, the shape of the particle size distribution depended on the resolution and the field-of-view. The ImageStream resolved single PCC particles, which has not previously been done using flow microscopy. Due to its limited field-of-view, the ImageStream could not measure the largest fines, which were detected by the Fiber Tester and Fiber Tester Plus. While the Fiber Tester Plus did not resolve single PCC particles, it detected, due to its higher resolution, a higher share of smaller particles than the Fiber Tester. Overall, the ImageStream and the Fiber Tester Plus were found to be complementary.The diffraction-based method struggled to measure small fines. It is proposed that small fines diffracted light insufficiently to be detected by the instrument. The obtained result was also highly sensitive to the choice of refractive index; a fact that some of the previous users apparently were not aware of.In summary, image-based methods were found to perform better than the diffraction-based method when measuring on fines and mixtures of fines and fillers, while the highest resolution image-based instrument and the diffraction-based method were best when measuring on pure fillers.
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| 3. |
- Vomhoff, Hannes, et al.
(författare)
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Evaluation of the compressibility of kitchen towel
- 2016
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Ingår i: Tappi Tissue 360 Forum.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The out-of-plane compressibility of kitchen towels is a very important product property in order to achieve a high absorption capacity. A method for the measurement of the compressibility was therefore developed. It allows the compression of a tissue sample by a defined pressure in the range between 0 and 30 kPa. The thickness of the sample is measured. Both single-ply base paper samples and fully converted multi-ply products can be evaluated. The measurement can be performed on both dry or wet samples. Multiple compressions of the samples can also be performed in order to evaluate the difference in plastic deformation as a result of consecutive compressions. Under normal conditions, the applied pressure is gradually increased from 0 to 30 kPa and then decreased back to 0 kPa. This procedure can then be repeated. The compressibility of the sample was evaluated in terms of a bulk versus applied pressure.The compressibility of different tissue grades was evaluated and compared. A clear difference in compressibility between standard DCT and structured tissue samples was observed. The first compression cycle lead to a considerable irreversible, plastic deformation of the sample. The plastic deformation decreased then considerably during the consecutive compression cycles. Wetting the samples lead to a considerable decrease in compressibility. The results allow interesting conclusions in terms of the influence of base sheet production process and the converting processes on the absorption properties.
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| 4. |
- Vomhoff, Hannes, et al.
(författare)
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Innventia Compression Test (ICT) : a method to measure compressibility of tissue products
- 2016
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Ingår i: Tissue World New Orleans 2016.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The out-of-plane compressibility of kitchen towels is a very important product property in order to achieve a high absorption capacity. A method for the measurement of the compressibility was therefore developed. It allows the compression of a tissue sample by a defined pressure between 0 and 30 kPa. The thickness of the sample is measured. Both single-ply base paper samples and fully converted multi-ply products can be evaluated. The measurement can be performed on both dry or wet samples. Multiple compressions of the samples can also be performed in order to evaluate the difference in plastic deformation as a result of consecutive compressions. Under normal conditions, the applied pressure is gradually increased from 0 to 30 kPa and then decreased back to 0 kPa. This procedure can then be repeated. The compressibility of the sample was evaluated in terms of a bulk versus applied pressure relationship. In the presentation, the method will be explained and the compressibility of different kitchen towel products will be presented and discussed. Using some example of results, the effect of sheet structure, multiple compressions and wetting of the samples and will be illustrated.
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