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  • 1.
    Gil-Castell, O.
    et al.
    Instituto de Tecnología de Materiales (ITM), Universidad Politecnica de Valencia (UPV), Valencia, Spain.
    Badia, J. D.
    Instituto de Tecnología de Materiales (ITM), Universidad Politecnica de Valencia (UPV), Valencia, Spain / Departament d'Enginyeria Química, Escola Tecnica Superior d'Enginyeria, Universitat de Valencia, Burjassot, Spain.
    Kittikorn, T.
    School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH e Royal Institute of Technology, Stockholm, Sweden / Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Songkhla, Thailand.
    Strömberg, E.
    School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH e Royal Institute of Technology, Stockholm, Sweden.
    Ek, M.
    School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH e Royal Institute of Technology, Stockholm, Sweden.
    Karlsson, Sigbritt
    University of Skövde. School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH Royal Institute of Technology, Stockholm, Sweden.
    Ribes-Greus, A.
    Instituto de Tecnología de Materiales (ITM), Universidad Politecnica de Valencia (UPV), Valencia, Spain.
    Impact of hydrothermal ageing on the thermal stability, morphology and viscoelastic performance of PLA/sisal biocomposites2016In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 132, p. 87-96Article in journal (Refereed)
    Abstract [en]

    The influence of the combined exposure to water and temperature on the behaviour of polylactide/sisal biocomposites coupled with maleic acid anhydride was assessed through accelerated hydrothermal ageing. The biocomposites were immersed in water at temperatures from 65 to 85 degrees C, between the glass transition and cold crystallisation of the PLA matrix. The results showed that the most influent factor for water absorption was the percentage of fibres, followed by the presence of coupling agent, whereas the effect of the temperature was not significant. Deep assessment was devoted to biocomposites subjected to hydrothermal ageing at 85 degrees C, since it represents the extreme degrading condition. The morphology and crystallinity of the biocomposites were evaluated by means of X-Ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The viscoelastic and thermal performance were assessed by means of dynamic mechanic thermal analysis (DMTA) and thermogravimetry (TGA). The presence of sisal generally diminished the thermal stability of the biocomposites, which was mitigated by the addition of the coupling agent. After composite preparation, the effectiveness of the sisal fibre was improved by the crystallisation of PLA around sisal, which increased the storage modulus and reduced the dampening factor. The presence of the coupling agent strengthened this effect. After hydrothermal ageing, crystallisation was promoted in all biocomposites therefore showing more fragile behaviour evidencing pores and cracks. However, the addition of coupling agent in the formulation of biocomposites contributed in all cases to minimise the effects of hydrothermal ageing. 

  • 2.
    Gil-Castell, O.
    et al.
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València, Valencia, Spain.
    Badia, J. D.
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València, Valencia, Spain / Departament de Química Orgànica i Analítica, Universitat Rovira i Virgili, Tarragona, Spain / Departament d’Enginyeria Química, Escola Tècnica Superior d’Enginyeria, Universitat de València, Burjassot, Spain.
    Strömberg, E.
    KTH Royal Institute of Technology, School of Chemical Science and Engineering, Fibre and Polymer Technology, Stockholm, Sweden.
    Karlsson, Sigbritt
    University of Skövde. KTH Royal Institute of Technology, School of Chemical Science and Engineering, Fibre and Polymer Technology, Stockholm, Sweden.
    Ribes-Greus, A.
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València, Valencia, Spain.
    Effect of the dissolution time into an acid hydrolytic solvent to taylor electrospun nanofibrous polycaprolactone scaffolds2017In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 87, p. 174-187Article in journal (Refereed)
    Abstract [en]

    The hydrolysis of the polycaprolactone (PCL) as a function of the dissolution time in a formic/acetic acid mixture was considered as a method for tailoring the morphology of nanofibrous PCL scaffolds. Hence the aim of this research was to establish a correlation between the dissolution time of the polymer in the acid solvent with the physicochemical properties of the electrospun nanofibrous scaffolds and their further service life behaviour. The physico-chemical properties of the scaffolds were assessed in terms of fibre morphology molar mass and thermal behaviour. A reduction of the molar mass and the lamellar thickness as well as an increase of the crystallinity degree were observed as a function of dissolution time. Bead-free fibres were found after 24 and 48 h of dissolution time with similar diameter distributions. The decrease of the fibre diameter distributions along with the apparition of beads was especially significant for scaffolds prepared after 72 h and 120 h of dissolution time in the acid mixture. The service life of the obtained devices was evaluated by means of in vitro validation under abiotic physiological conditions. All the scaffolds maintained the nanofibrous structure after 100 days of immersion in water and PBS. The molar mass was barely affected and the crystallinity degree and the lamellar thickness increased along immersion preventing scaffolds from degradation. Scaffolds prepared after 24 h and 48 h kept their fibre diameters whereas those prepared after 72 h and 120 h showed a significant reduction. This PCL tailoring procedure to obtain scaffolds that maintain the nanoscaled structure after such long in vitro evaluation will bring new opportunities in the design of long-term biomedical patches. 

  • 3.
    Le Normand, Myriam
    et al.
    KTH Royal Institute of Technology.
    Moriana, Rosana
    KTH Royal Institute of Technology.
    Ek, Monica
    KTH Royal Institute of Technology.
    Isolation and characterization of cellulose nanocrystals from spruce bark in a biorefinery perspective2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 111, p. 979-987Article in journal (Refereed)
    Abstract [en]

    The present study reports for the first time the isolation of cellulose fibers and cellulose nanocrystals (CNCs) from the bark of Norway spruce. The upgrading of bark cellulose to value-added products, such as CNCs, is part of the "bark biorefinery" concept. The removal of non-cellulosic constituents was monitored throughout the isolation process by detailed chemical composition analyses. The morphological investigation of the CNCs was performed using AFM and showed the presence of nanocrystals with an average length of 175.3 nm and a diameter of 2.8 nm, giving an aspect ratio of around 63. X-ray diffraction (XRD) analyses showed that the crystallinity index increased with successive treatments to reach a final value greater than 80% for CNCs. The thermal degradation of the isolated bark CNCs started at 190 degrees C Spruce bark appeared to be a new promising industrial source of cellulose fibers and CNCs.

  • 4.
    Moriana, Rosana
    et al.
    Universidad Politécnica de Valencia, Spain.
    Vilaplana, Francisco
    KTH – Royal Institute of Technology.
    Karlsson, Sigbritt
    KTH – Royal Institute of Technology.
    Ribes-Greus, Amparo
    Universidad Politécnica de Valencia, Spain.
    Improved thermo-mechanical properties by the addition of natural fibres in starch-based sustainable biocomposites2011In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 42, no 1, p. 30-40Article in journal (Refereed)
    Abstract [en]

    Sustainable biocomposites based on thermoplastic starch copolymers (Mater-Bi KE03B1) and biofibres (cotton, hemp and kenaf) were prepared and characterised in terms of their thermo-mechanical and morphological properties. Biocomposites exhibit improved thermal stability and mechanical properties in comparison with the Mater-Bi KE. Biofibres act as suitable thermal stabilizers for the Mater-Bi KE, by increasing the maximum decomposition temperature and the Ea associated to the thermal decomposition process. Biofibre addition into the Mater-Bi KE results in higher storage modulus and in a reduction of the free-volume-parameter associated to the Mater-Bi KE glass transition. The influence of different biofibres on the thermo-mechanical properties of the biocomposites has been discussed. Hemp and kenaf enhance the thermal stability and reduce the free volume-parameter of Mater-Bi KE more significantly than cotton fibres, although the latter exhibits the highest mechanical performance. These differences may be explained by the improved interaction of lignocellulosic fibres with the Mater-Bi KE, due to the presence of hemicellulose and lignin in their formulation. © 2010 Elsevier Ltd. All rights reserved.

  • 5.
    Moriana, Rosana
    et al.
    KTH Royal Institute of Technology.
    Zhang, Yujia
    KTH Royal Institute of Technology.
    Mischnick, Petra
    Technische Universität Braunschweig, Germany.
    Li, Jiebing
    KTH Royal Institute of Technology.
    Ek, Monica
    KTH Royal Institute of Technology / Chalmers University of Technology.
    Thermal degradation behavior and kinetic analysis of spruce glucomannan and its methylated derivatives2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 106, no 1, p. 60-70Article in journal (Refereed)
    Abstract [en]

    The thermal degradation behavior and kinetics of spruce glucomannan (SGM) and its methylated derivatives were investigated using thermogravimetric analysis to characterize its temperature-dependent changes for use in specific applications. The results were compared with those obtained for commercial konjac glucomannan (KGM). The SGM and the KGM exhibited two overlapping peaks from 200 to 375 C, which correspond to the intensive devolatilization of more than 59% of the total weight. Differences in the pyrolysis-product distributions and thermal stabilities appeared as a result of the different chemical compositions and molecular weights of the two GMs. The Friedman and Flynn-Wall-Ozawa isoconversional methods and the Coats-Redfern were adopted to determine the kinetic triplet of the intensive devolatilization region. Both GMs can be modeled using a complex mechanism that involves both a Dn-type and an Fn-type reaction. The comparative study of partially methylated GM indicated higher homogeneity and thermal resistance for the material with the higher degree of substitution.

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