Preparation of hemp fibres for advanced bio-composite applications

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School of Chemical Engineering | Master's thesis
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SO<sup>2</sup>-ethanol-water (SEW) pulping has been introduced as a possible means of separating hemp technical fibres (fibre bundies) into fibre cultivates (single fibre). Results about both the chemical and physical behaviour of SEW treated hemp fibres are presented. This study was carried out with respect to conditions of pulping time, temperature and SO<sup>2</sup> concentration. The experiments were carried out at the input level of SO<sup>2</sup> concentrations of 4, 8 and 12 % and 55 % (vol.) ethanol/H<sup>2</sup>O at temperatures of 115°C to 145°C and pulping times from 10 minutes to 90 minutes. As a part of this study, the fibre separation process was evaluated from the result of dry matter contents, yield, viscosity and microscopy. Treated fibres at lower temperature show higher yield (%) but at higher SO<sup>2</sup> concentrations showed lower yield (%). The viscosity of the SEW treated fibre is decreased with an increase of treatment time and temperature which is also same for higher SO<sup>2</sup> concentrations. It was also observed from the optical micrographs that increased cooking time and temperature made the fibre separation process more effective. SEW treated fibre shows higher elastic modulus but most of the sample shows lower tensile strength than untreated fibre. There is a correlation between viscosity and tensile strength, i.e. tensile strength increases with increasing viscosity. The mechanical properties of epoxy-hemp composites were investigated. The tensile strength of SEW treated hemp-epoxy composites were increased due to the removal of debris, fibre separation and surface roughness of treated fibre compared to the untreated fibre.
Hughes, Mark
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Hänninen, Tuomas
hemp, SEW pulping, viscosity, composites
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