Scaling of xylem and phloem transport capacity and resource usage with tree size

Peer reviewe

Kemiallisilla reaktioilla stabiloitu nanoselluloosa / polyesteri komposiitti

Cellulose nanofibrils have attracted interest among researchers in the past decade due to their interesting properties (mechanical strength, flow behaviour and optical), which could have large industrial potential. However, the processing methods used are often not industrially viable and there is a gap between the state of the research and commercialization of the material. In this study we aim to solve this problem by introducing a method to incorporate TEMPO oxidized nanocellulose (ToNC) in conventional alkyd resin processing, without doing any additional chemical treatments. The study first gives a theoretical overview to cellulose, nanocelluloses, TEMPO mediated oxidation, polymers (especially polyesters), rheology and composites. The theoretical overview is then followed by experimental part which introduces methods used in this study: TEMPO mediated oxidation and characterization of carboxylic content in ToNC by conductometric titration, principles of alkyd resin and polyester formulations, acid value measurements, solid state polymerization (including scanning electron microscopy imaging), flow viscosity measurements with oscillatory rheometry, ATR-FTIR spectroscopy, water retention values and novel methods for ToNC spinning. The results show that uniform dispersions can be achieved by processing ToNC with glyptal oligomers. The formed suspensions are clear and no aggregation is seen even when the polymerization is carried to completion in a solid state polymerization. The ToNC was noticed to alter the flow behaviour of the glyptal oligomer in a great extent, showing a strong pseudoplastic behavior. Additionally, the water retention capacity of ToNC was changed by addition of short polyester oligomers whereas larger oligomers did not seem to have any effect into the water retention capacity of ToNC. Finally it was noticed that polyester oligomers increased the wet-strength of syringe spun ToNC filament. The method proposed in this thesis could simplify the processing of ToNC and thus promote the attractiveness of ToNC for industrial applications. Especially, ToNC and polyester composites could have industrial potential in material applications such as paints and biocompositesNanocelluloosa on ollut erittäin tutkittu aihe viimeisen vuosikymmenyksen aikana. Sillä on erittäin kiinnostavia ominaisuuksia (mekaaninen lujuus, virtaus mekaniikka ja optiset ominaisuudet), joilla voisi olla paljon teollisia mahdollisuuksia. Akateemisessa tutkimuksessa käytetyt valmistus menetelmät ovat kuitenkin huonosti soveltuvia teolliseen käyttöön. Eli nykyisen tutkimuksen ja materiaalin kaupallistamisen välillä on aukko, johon tämä diplomi työ on suunnattu. Tässä työssä prosessoimme Tempo hapetettua nanoselluloosaa (ToNC) alkydin kanssa ilman erilaisia kemiallisia esikäsittelyitä. Ensiksi esittelemme selluloosan, nanoselluloosien, Tempo hapetuksen, polymeerien (erityisesti polyesterien), rheologian ja komposiittien teoreettisen taustan. Tämän jälkeen siirrymme kokeelliseen osuuteen, jossa käydään läpi työssä käytetyt metodit, kuten Tempo hapetus ja sen tuloksen karakterisoiminen konduktometrisellä titrauksella, alkydi reseptit laskut, happoluvun määritys, polyestereiden valmistus, kiinteä polymerisointi, virtaus viskositeetti mittaukset, ATRFTIR spectroskopia, kustomoitu vedensitomistesti ja uusi metodi ToNC langan valmistukseen. Tuloksista voidaan huomata, että on mahdollista muodostaa yhtenäinen seos ToNC:sta ja glyptalista eikä paakkuja havaittu, vaikka polymerisointi vietiin loppuun asti kiinteä polymerisoinnissa. ToNC huomattiin myös muuttavan glyptalin virtausominaisuuksia suuresti. ToNC lisäys toi seokseen vahvan pseudoplastisen virtausprofiilin. Myös ToNC veden sitominen muuttui kun siihen lisäsi lyhyitä polyesteri oligomeerejä. Pitemmillä polyesteri oligomeereillä ei puolestaan ollut vaikutusta vedensitomiseen. Lisäksi polyester oligomeerit näyttivät lisäävän ToNC langan märkälujuutta. Työssä käytetty metodi ToNC ja polyesterien prosessointiin mahdollistaa hydrofobisen ja hydrofiilisen faasin yhteen liittämisen ilman erillisiä kemiallisia käsittelyitä ja voi täten lisät ToNC kiinnostavuutta teollisiin tarkoituksiin. Erityisesti ToNC ja polyesteri komposiitit maali ja biokomposiitti tarkoituksiin ovat teollisesti kiinnostavia

Direct measurements of non-ionic attraction and nanoscaled lubrication in biomimetic composites from nanofibrillated cellulose and modified carboxymethylated cellulose

VK: T10413 50 %; T10402 50 %There is a growing interest to design biomimetic self-assembled composite films from renewable resources aimed at a combination of high toughness, strength and stiffness. However, the relationship between interfacial interactions of the components and the mechanical performance of the composite is still poorly understood. In this work we present evidence of the link between mechanical performance of carbohydrate-based composites with nanolubrication and with direct surface forces between the hard and soft domain in the system. Our approach was to use nanofibrillated cellulose (NFC) as the major reinforcing domain and to modify it by adsorption of a small amount of soft polyethylene glycol grafted carboxymethyl cellulose (CMC-g-PEG). The effect of the soft polymer on direct normal and friction forces in air between cellulose surfaces was evaluated using colloidal probe microscopy. The fibrillar structure of the NFC thin film affected the frictional behaviour; when decreasing load, the friction between pure cellulose surfaces increased, suggesting partial pull-out of fibrils, a phenomenon not observed for non-fibrillar cellulose substrates. Adsorption of CMC-g-PEG on both surfaces decreased the friction considerably but adhesion was still high. The symmetric system, having both cellulose substrates covered with polymer, was compared to asymmetric systems where only one surface was covered with polymer. Furthermore, a free standing composite film was prepared by non-ionic self-assembly of NFC and CMC-g-PEG with 99:1 weight-ratio; the mechanical properties of the macroscopic films were related to the nanoscaled interactions between the components. The composition studied showed excellent mechanical properties which do not follow the simple rule of mixture. Thus, a synergy in the direct surface forces and mechanical properties was found. This approach offers a robust path to aid in the efficient design of next generation biomimetic composites.Peer reviewe