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- Asta, Nadia
(författare)
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Fundamentals of Interactions between Cellulose Materials and its Implications on Properties of Fibrous Networks
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fundamental research plays a pivotal role in the development of sustainable solutions that benefit both our environment and everyday lives. Cellulose, as an abundant and renewable resource, holds immense potential for sustainable applications. However, navigating the complexities of molecular and supramolecular structure of cellulose poses significant challenges in harnessing its full potential. By delving into fundamental research, we aim to uncover the underlying mechanisms governing cellulose interactions, paving the way for innovative advancements in sustainable material development.This thesis uncovers the intricate relationship between fundamental research and applied methodologies by showing how molecular contact and structure at the interface of cellulose-rich materials will control the development of the macroscopic mechanical properties of networks from cellulose-rich fibres. The study encompasses various facets, ranging from the development of model materials for studying interfacial interactions to the preparation of fibrous networks with tailored properties.In the initial part of the work the research delves into the development of model materials to investigate interactions at smooth interfaces of regenerated cellulose. The study reveals the crucial role of the making and breaking of cellulose interface, or sometimes interphase, in the development of adhesive joints. Experimental findings demonstrate how chemical additives influence the interactions between cellulose surfaces, thereby modulating the structural and adhesive properties at the interface. Furthermore, by utilizing model materials, insights are gained into fibre-fibre interactions and the influence of surface treatments on network formation and mechanical performance. Lastly, the research focused on investigating the preparation of fibrous networks at different densities and amount of adsorbed additives, providing a comprehensive understanding of how network density and composition affect mechanical properties of the networks.This work not only exemplifies a synergistic approach, where fundamental insights into molecular contacts and interface structures are translated into practical applications for enhancing macroscopic properties but also highlights the importance of integrating fundamental and applied methodologies in molecular engineering, offering novel strategies for advancing sustainable paper production practices and contributing to the attainment of sustainable development goals.
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| 4. |
- Asta, Nadia, et al.
(författare)
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Model systems for clarifying the effects of surface modification on fibre–fibre joint strength and paper mechanical properties
- 2024
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Ingår i: Cellulose. - : Springer Science and Business Media B.V.. - 0969-0239 .- 1572-882X.
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Tidskriftsartikel (refereegranskat)abstract
- The growing demand for sustainable products has spurred research into renewable materials, with cellulose-based materials emerging as prominent candidates due to their exceptional properties, abundance, and wide-ranging applications. In this context, there is a need to develop a better fundamental understanding of cellulose interactions such that we can continue to design and improve sustainable materials. Individual interactions can be difficult to assess in bulk fibre-based materials and therefore cellulose model materials have become indispensable tools for researchers as they can facilitate the study of cellulose interactions at a molecular level enabling the design of sustainable materials with enhanced properties. This study presents a new methodology for studying the effects of surface treatments on the individual fibre–fibre joint strength using wet-spun cellulose nanofiber (CNF) filaments as model materials. The Layer-by-Layer assembly technique is used to modify the surface chemistry of the model materials as well as bleached and unbleached hardwood Kraft fibres, demonstrating its potential to enhance adhesive properties and overall mechanical performance of papers made from these fibres. The study further explores the impact of increasing network density through wet-pressing during paper preparation, showcasing a comprehensive approach to molecularly tailor fibre-based materials to achieve superior mechanical properties. The proposed methodology provides a time-efficient evaluation of chemical additives in paper preparation.
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| 5. |
- Asta, Nadia, et al.
(författare)
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The Use of Model Cellulose Materials for Studying Molecular Interactions at Cellulose Interfaces
- 2023
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 12, s. 1530-1535
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Tidskriftsartikel (refereegranskat)abstract
- Despite extensive research on biobased and fiber-based materials, fundamental questions regarding the molecular processes governing fiber-fiber interactions remain unanswered. In this study, we introduce a method to examine and clarify molecular interactions within fiber-fiber joints using precisely characterized model materials, i.e., regenerated cellulose gel beads with nanometer-smooth surfaces. By physically modifying these materials and drying them together to create model joints, we can investigate the mechanisms responsible for joining cellulose surfaces and how this affects adhesion in both dry and wet states through precise separation measurements. The findings reveal a subtle balance in the joint formation, influencing the development of nanometer-sized structures at the contact zone and likely inducing built-in stresses in the interphase. This research illustrates how model materials can be tailored to control interactions between cellulose-rich surfaces, laying the groundwork for future high-resolution studies aimed at creating stiff, ductile, and/or tough joints between cellulose surfaces and to allow for the design of high-performance biobased materials.
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| 6. |
- Li, Hailong, et al.
(författare)
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Reevaluation of the adhesion between cellulose materials using macro spherical beads and flat model surfaces
- 2024
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 332, s. 121894-121894
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between dry cellulose were studied using model systems, cellulose beads, and cellulose films, usingcustom-built contact adhesion testing equipment. Depending on the configuration of the substrates in contact,Polydimethylsiloxane (PDMS) film, cellulose films spin-coated either on PDMS or glass, the interaction showsthree distinct processes. Firstly, molecular interlocking is formed between cellulose and cellulose when there is asoft PDMS thin film backing the cellulose film. Secondly, without backing, no initial attraction force between thesurfaces is observed. Thirdly, a significant force increase, ΔF, is observed during the retraction process for cellulose on glass, and there is a maximum in ΔF when the retraction rate is increased. This is due to the kinetics of acontacting process occurring in the interaction zone between the surfaces caused by an interdigitation of a finefibrillar structure at the nano-scale, whereas, for the spin-coated cellulose surfaces on the PDMS backing, there isa more direct adhesive failure. The results have generated understanding of the interaction between cellulose-rich materials, which helps design new, advanced cellulose-based materials. The results also show thecomplexity of the interaction between these surfaces and that earlier mechanisms, based on macroscopic materialtesting, are simply not adequate for molecular tailoring.
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| 7. |
- Li, Hailong, et al.
(författare)
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Structure Development of the Interphase between Drying Cellulose Materials Revealed by In Situ Grazing-Incidence Small-Angle X-ray Scattering
- 2021
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 22:10, s. 4274-4283
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Tidskriftsartikel (refereegranskat)abstract
- The nano- to microscale structures at the interface between materials can define the macroscopic material properties. These structures are extremely difficult to investigate for complex material systems, such as cellulose-rich materials. The development of new model cellulose materials and measuring techniques has opened new possibilities to resolve this problem. We present a straightforward approach combining micro-focusing grazing-incidence small-angle X-ray scattering and atomic force microscopy (AFM) to investigate the structural rearrangements of cellulose/cellulose interfaces in situ during drying. Based on the results, we propose that molecular interdiffusion and structural rearrangement play a major role in the development of the properties of the cellulose/cellulose interphase; this model is representative of the development of the properties of joint/contact points between macroscopic cellulose fibers.
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