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Green Nanocomposites from Cereal Husk
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
2018 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Gröna nanokompositmaterial från spannmål (Swedish)
Abstract [en]

The aim of this master thesis study was to investigate the possibility to extract cellulose nanocrystals (CNC) from cereal husks and their capability to be used as reinforcement systems of hemicellulosic biopolymers. CNC were isolated from rye husk and used as reinforcement in nanocomposites. To obtain the isolated CNC the rye husk was processed through alkaline treatments, bleaching treatments and finally an acid hydrolysis. The cellulose extraction was optimized and optimal conditions were reached when 3wt% of rye husk were used for both alkaline and bleaching treatments. Acid hydrolysis was performed at 45°C for 30 minutes. The total yield from the rye husk to the CNCs was approximately 11wt%. The isolation process from macro to nano size was monitored via different chemico-physical characterization methods.

Via Scanning Electron Microscopy (SEM) analysis, the isolation of the cellulose fibers from rye husk could be assessed. The chemical composition was evaluated via carbohydrate analysis, ash, extractives and lignin Klason determination. From these chemical data, it was verified that most of the amorphous components of the rye husk were removed reaching 73.17% of cellulose for the isolated cellulose fibers. Fourier transform infrared spectroscopy (FTIR) was used to follow the chemical structural changes through the CNC isolation process. From the FTIR spectra, it could be seen that the bleached husk and CNC materials were similar to a cellulose fiber compared to the rye husk and alkaline treated husk, which had FTIR spectra typical for lignocellulosic biomass. This fact indicates that most of the hemicellulose and lignin were removed due to the chemical treatments the rye husk was submitted to. Crystalline index of the samples was also determined with FTIR and an increasing crystallinity trend was observed through the isolation, from rye husk to CNC. The Thermogravimetric Analysis (TGA) was used to assess the thermal stability and it was observed that the bleached and CNC samples had an increased thermal stability with respect to the lignocellulosic and alkaline samples, indicating the most labile components of the rye husk were removed. The rye husk CNC exhibited a length of 335.4 nm, diameter of 2.86 nm and a zeta potential of -35.8 mV together with a high purity (>98% of cellulose) crystallinity and thermal stability.

Green nanocomposites based on commercial arabinoxylan from rye and CNC isolated from rye husk were prepared. The method employed to produce the nanocomposite films was solvent casting. Different amounts of CNC were added to the arabinoxylan matrix: 0, 5, 10 and 20wt% of CNC. Mechanical and thermal properties of the nanocomposites were evaluated. The nanocomposite films exhibited an increase in the thermal stability, Young modulus and tensile strength due to the addition of the CNC indicating a good compatibility and interaction between the raw materials.

Place, publisher, year, edition, pages
2018.
Keywords [en]
Cereal residues, Green nanocomposites, Rye, Nanocellulose, Cellulose nanocrystals
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-224760OAI: oai:DiVA.org:kth-224760DiVA, id: diva2:1192421
Available from: 2018-03-22 Created: 2018-03-22 Last updated: 2018-03-22Bibliographically approved

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