SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Larsson Helena) ;lar1:(ri)"

Sökning: WFRF:(Larsson Helena) > RISE

  • Resultat 1-7 av 7
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  •  
2.
  •  
3.
  •  
4.
  • Halonen, Helena, et al. (författare)
  • Mercerized cellulose biocomposites : A study of influence of mercerization on cellulose supramolecular structure, water retention value and tensile properties
  • 2013
  • Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 20:1, s. 57-65
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study the effect of the mercerization degree on the water retention value (WRV) and tensile properties of compression molded sulphite dissolving pulp was evaluated. The pulp was treated with 9, 10, or 11 % aqueous NaOH solution for 1 h before compression molding. To study the time dependence of mercerization the pulp was treated with 12 wt% aqueous NaOH for 1, 6 or 48 h. The cellulose I and II contents of the biocomposites were determined by solid state cross polarization/magic angle spinning carbon 13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. By spectral fitting of the C6 and C1 region the cellulose I and II content, respectively, could be determined. Mercerization decreased the total crystallinity (sum of cellulose I and cellulose II content) and it was not possible to convert all cellulose I to cellulose II in the NaOH range investigated. Neither increased the conversion significantly with 12 wt% NaOH at longer treatment times. The slowdown of the cellulose I conversion was suggested as being the result from the formation of cellulose II as a consequence of coalescence of anti-parallel surfaces of neighboring fibrils (Blackwell et al. in Tappi 61:71–72, 1978; Revol and Goring in J Appl Polym Sci 26:1275–1282, 1981; Okano and Sarko in J Appl Polym Sci 30:325–332, 1985). Compression molding of the partially mercerized dissolving pulps yielded biocomposites with tensile properties that could be correlated to the decrease in cellulose I content in the pulps. Mercerization introduces cellulose II and disordered cellulose and lowered the total crystallinity reflected as higher water sensitivity (higher WRV values) and poorer stiffness of the mercerized biocomposites.
  •  
5.
  • Komazec, Ksenija, et al. (författare)
  • Building a Tiny House from Waste An alternative platform for exploring sustainability
  • 2023
  • Ingår i: FormAkademisk. - : The Assosiation FormAkademisk. - 1890-9515. ; 16:4
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper contributes to the understanding of how critical reflection can be applied to sustainability. This was accomplished by tracing the progression of a tiny-house project over time and the associated activities, which involved sourcing secondhand and discarded materials. We are a group of researchers and practitioners who worked together to explore and challenge the established norms of sustainability in housing practices: who is building, what is being built, with what materials, and through which processes. The use of discarded materials as resources for building a tiny house came to be decisive in shaping a platform for inclusion and sustainable practices. While the most common practice of building involves buying the materials needed at a lumber yard, working with discarded and secondhand materials requires time and flexibility. Tools play a central role in adapting random waste to specific purposes, a process that also demands skills in handling tools creatively. Additionally, gathering, organizing, and cleaning are activities that should be given special attention when working with these types of materials. In this paper, we explain how we reinjected waste materials into the production chain and how our work contributes to sustainable development from environmental and social perspectives. The argument for sustainability in our research revolves around exploring processes that include more groups in society and alternative ways of organizing the resources available.
  •  
6.
  • Nilsson, Helena, et al. (författare)
  • Compression molded wood pulp biocomposites : A study of hemicellulose influence on cellulose supramolecular structure and material properties
  • 2012
  • Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19:3, s. 751-760
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, the importance of hemicellulose content and structure in chemical pulps on the property relationships in compression molded wood pulp biocomposites is examined. Three different softwood pulps are compared; an acid sulfite dissolving grade pulp with high cellulose purity, an acid sulfite paper grade pulp and a paper grade kraft pulp, the latter two both containing higher amounts of hemicelluloses. Biocomposites based the acid sulfite pulps exhibit twice as high Young's modulus as the composite based on paper grade kraft pulp, 11-12 and 6 GPa, respectively, and the explanation is most likely the difference in beating response of the pulps. Also the water retention value (WRV) is similarly low for the two molded sulfite pulps (0.5 g/g) as compared to the molded kraft pulp (0.9 g/g). The carbohydrate composition is determined by neutral sugar analysis and average molar masses by SEC. The cellulose supramolecular structure (cellulose fibril aggregation) is studied by solid state CP/MAS 13C-NMR and two forms of hemicellulose are assigned. During compression molding, cellulose fibril aggregation occurs to higher extent in the acid sulfite pulps as compared to the kraft pulp. In conclusion, the most important observation from this study is that the difference in hemicellulose content and structure seems to affect the aggregation behaviour and WRV of the investigated biocomposites.
  •  
7.
  • Zhou, Qi, et al. (författare)
  • Nanostructured biocomposites based on bacterial cellulosic nanofibers compartmentalized by a soft hydroxyethylcellulose matrix coating
  • 2009
  • Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 5:21, s. 4124-4130
  • Tidskriftsartikel (refereegranskat)abstract
    • Biomimetic approaches involving environmentally-friendly synthetic pathways provide an opportunity to elaborate novel high-performance biocomposites. Here we have developed a low-energy biosynthetic system for the production of a high-strength composite material consisting of self-assembled and nanostructured cellulosic nanofibers. This biocomposite is analogous to natural composite materials with high strength and hierarchical organization such as wood or tendon. It was generated by growing the bacterium Acetobacter, which naturally produces cellulosic nanofibers, in the presence of hydroxyethylcellulose (HEC). Individual cellulose fibrils were coated by HEC and exhibited a smaller lateral dimension than pure bacterial cellulose (BC) fibrils. They self-assembled to form compartmentalized nanofibers and larger cellulose fibril aggregates compared to pure BC. The tensile strength of nanocomposite films prepared from the compartmentalized cellulosic nanofibers was 20% higher than that of pure BC sheets and wood cellulose nanopapers, and 60% higher than that of conventional BC/HEC blends, while no strain-to-failure decrease was observed. The thin nanoscale coating consisting of hydrated HEC significantly increased the mechanical performance of the nanocomposite films by provoking compartmentalization of individual fibrils.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-7 av 7

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy