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Gewählte Doctoral Thesis:

Marta Hrabalova (2011): VISCOELASTIC AND THERMAL PROPERTIES OF NATURAL FIBRE-REINFORCED COMPOSITES.
Doctoral Thesis - Institut für Holzforschung (IHF), BOKU-Universität für Bodenkultur, pp 86. UB BOKU obvsg FullText

Data Source: ZID Abstracts
Abstract:
This study focuses on viscoelastic and thermal properties of composites using thermoplastic biodegradable matrices and cellulose-based fibreous fillers. First, interactions among these components were studied by looking at properties relative to processing conditions and physical or chemical modification of fillers, and the polymer matrix. Processing alterations were applied to softwood flour filled Polylactic acid (PLA) films. Responses were investigated using differential scanning calorimetry, dynamic mechanical analysis, and scanning electron microscopy. It was found that material properties improve with thermal annealing. The second part of the thesis was concerned with PLA materials, filled with different tissue types (i.e. mature, juvenile, compression wood) of Sitka spruce wood. Wood fibers were treated with vinyltrimethoxysilane, while the polymer matrix was modified with 4,4'-methylene-diphenyl-diisocyanate. It is shown that treatments improved thermal and mechanical properties, and the potential of by utilizing the natural variability of wood fibres is shown. Nano-fibrilated cellulose (NFC) was produced from flax and wheat straw pulps through high pressure disintegration. The reinforcing potential of the nano-fibrils in a polyvinyl-alcohol matrix was evaluated. It is shown that selection of the appropriate raw cellulose is indispensable for the functional optimization of composite products. Improvement with NFC was most remarkable. This is mainly assigned to the structural features of the NFC filler. Finally, the influence of surface modification of beech wood flour in polyhydroxybutyrate (PHB)-based composites was investigated. In addition to hydrothermal treatment, NaOH and stearic acid were both used as surface modifiers. While interfacial bonding between PHB and the wood fibres was weak without hydrothermal treatment, the surface modifiers in combination with hydrothermally pretreated wood fibres significantly improved the material performance.

Betreuer: Wimmer Rupert

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