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Kulkarni, Rohan AjitORCID iD iconorcid.org/0000-0003-0723-5593
Publications (4 of 4) Show all publications
Kulkarni, R. A. (2024). Structural changes in cellulose fibres under extreme pressure. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Structural changes in cellulose fibres under extreme pressure
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cellulose, the most abundant biopolymer on Earth, offers tremendous potential for sustainable materials and bio-based products. Understanding the interplay between processing parameters and the cellulose fiber structure is vital for optimizing manufacturing processes and advancing sustainable materials science. This thesis presents a comprehensive investigation into the effects of dynamictimescales and the magnitude of pressure on cellulose fibres’ hierarchical structureand properties, encompassing a range of experimental techniques andmethodologies. The initial study focuses on the dynamic compression and decompression of wet cellulose pulp fibers using shock waves, aiming to modify the cell wall structure significantly. By subjecting wet cellulose pulp samples to rapid high pressure pulses (10 ms long, 300 MPa peak pressure), we hypothesize that we observe increased accessibility to the fibre interior by inducing weak spots in the cell wall. Characterization techniques, including scanning electron microscopyand X-ray diffraction, reveal a decrease in crystallinity and changes in surfacemorphology, indicating structural modifications induced by the rapid pressurepulse. Subsequently, we delve into a detailed investigation of pressure induced changes to the cellulose fiber structure using in-situ and ex-situ X-ray diffraction techniques with a resistive-heated diamond anvil cell (DAC). During the in-situ experiment, we track crystalline changes in real-time during static extreme-pressure conditions, providing insights into the kinetics of cellulose transformation under pressure. In the ex-situ experiment, we examine post decompression properties to assess the retention of structural modifications induced by pressure. Additional bulk measurements using various characterizationtechniques corroborate the findings, confirming the structural changesobserved in situ. Finally, we explore a novel approach involving slow compression and fast decompression, reminiscent of a steam explosion technique, to induce destructive changes in cellulose fiber structure. This study, albeit destructive, provides valuable insights into the limits of cellulose modification under extreme processing conditions, offering perspectives on the feasibility and implications of such approaches.In conclusion, this thesis presents a comprehensive examination of pressure induced modifications in cellulose fiber structure, highlighting the critical role of processing parameters in regulating cellulose properties. By elucidating the intricate relationship between pressure application timescales, magnitudes, and structural outcomes, we pave the way for developing tailored cellulose-based materials with enhanced functionalities and sustainability.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2024
Series
TRITA-SCI-FOU ; 2024:58
National Category
Engineering and Technology
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-356524 (URN)978-91-8106-138-3 (ISBN)
Public defence
2024-12-09, F3, Lindstedtsvägen 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation, 76273
Note

QC 241118

Available from: 2024-11-18 Created: 2024-11-15 Last updated: 2024-11-18Bibliographically approved
Kulkarni, R. A., Apazidis, N., Larsson, P. T., Lundell, F. & Söderberg, D. (2023). Experimental studies of dynamic compression of cellulose pulp fibers. Sustainable Materials and Technologies, 38, Article ID e00774.
Open this publication in new window or tab >>Experimental studies of dynamic compression of cellulose pulp fibers
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2023 (English)In: Sustainable Materials and Technologies, ISSN 2214-9937, Vol. 38, article id e00774Article in journal (Refereed) Published
Abstract [en]

The ability to control the structure of the wood-pulp fiber cell wall is an attractive means to obtain increased accessibility to the fiber interior, providing routes for functionalization of the fibers that support further processing and novel material concepts, e.g. improved degree of polymerization, nanofiltration as demonstrated in previous studies. It has been proposed that dynamic compression and decompression of the cellulose pulp fibers in the wet state make it possible to modify the cell wall significantly. We hypothesize that hydrostatic pressure exerted on fibers fully submerged in water will increase the accessibility of the fiber wall by penetrating the fiber through weak spots in the cell wall. To pursue this, we have developed an experimental facility that can subject wet cellulose pulp samples to a pressure pulse -10 ms long and with a peak pressure of -300 MPa. The experiment is thus specifically designed to elucidate the effect of a rapid high-pressure pulse passing through the cellulose sample and enables studies of changes in structural properties over different size ranges. Different characterization techniques, including Scanning electron microscopy, X-ray diffraction, and wide- and small-angle X-ray scattering, have been used to evaluate the material exposed to pulsed pressure. The mechanism of pressure build-up is estimated computationally to complement the results. Key findings from the experiments consider a decrease in crystallinity and changes in the surface morphology of the cellulose sample.

Place, publisher, year, edition, pages
Elsevier BV, 2023
Keywords
Cellulose fiber modification, Dynamic compression, Accessibility, Cell wall, High-pressure, X-ray scattering, Computations
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-341813 (URN)10.1016/j.susmat.2023.e00774 (DOI)001122972200001 ()2-s2.0-85179623066 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20240103

Available from: 2024-01-03 Created: 2024-01-03 Last updated: 2024-11-18Bibliographically approved
Kulkarni, R. A., Giordano, N., Gordeyeva, K., Lundell, F. & Söderberg, D. In-situ characterisation of cellulose-rich pulpsunder extreme conditions.
Open this publication in new window or tab >>In-situ characterisation of cellulose-rich pulpsunder extreme conditions
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(English)In: Article in journal (Refereed) Submitted
Abstract [en]

Studies of molecular changes in cellulose structure as a response to different physical conditions are essential for understanding the fundamental mechanisms that can be used to optimise processing conditions and contribute to improved sustainability. Cellulose strongly interacts with water, raising the question of whether it is possible to change its molecular structure by changing the physical structure and properties of the surrounding water. Previous studies have established that the hyperbaric treatment of bio-materials permanently affects molecular structure in terms of crystallinity and accessibility. The present study shows the changes in cellulose-rich pulps on the molecular level in response to static extreme-pressure conditions. This is achieved by statically compressing the pulp-water mixture up to 3 GPa pressure using a resistive-heated di-amond anvil cell (DAC). During compression, the water transforms through a phase transformation from liquid to ice VI and ice VII, inducing a permanent increase in the crystallinity of the pulp. High-pressure, cellulose, X-ray diffraction, diamond anvil cell, crystallinity, morphological changes

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-356520 (URN)
Note

QC 20241118

Available from: 2024-11-15 Created: 2024-11-15 Last updated: 2024-11-18Bibliographically approved
Kulkarni, R. A., Larsson, P. T., Lundell, F. & Söderberg, D. Structural Changes in Cellulose-rich PulpsUnder Extreme Static Conditions.
Open this publication in new window or tab >>Structural Changes in Cellulose-rich PulpsUnder Extreme Static Conditions
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The ability to modify the structure of the wood-pulp fibre cell wall structure is an attractive means to obtain increased accessibility to the fibre interior and enable functionalization such as controlled drug delivery, interpenetrated networks, and selective removal of metal ions from aqueous mixtures just to mention a few examples. By changing the physical state of water, it should be possible to significantly alter the structure of the wet fibre wall, providing the possibility to perform cell wall modifications under extreme conditions. To address this challenge, we have focussed on investigating the structural development of the wet softwood kraft pulp fibre wall under high pressure (HP) conditions (up to 2 GPa). The experiments aim to clarify the effect of the HP conditions on the porosity and the accessibility of the fibre wall for treated and untreated fibres. The second goal is to observe the changes in the crystalline structure of cellulose due to HP conditions. Different characterization techniques, including Electron microscopy, X-ray diffraction, Small and wide-angle X-ray scattering, and Cross-polarized/magic angle spinning 13C-NMR, are used to characterize material that has been exposed to HP. Key findings from the experiments relate to changes in crystallinity, specific surface area, bound water content and surface morphology.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-356521 (URN)
Note

QC 20241118

Available from: 2024-11-15 Created: 2024-11-15 Last updated: 2024-11-18Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-0723-5593

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