| 1. |
- Ezekiel, Ngesa, et al.
(författare)
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Effect of temperature and durations of heating on coir fibers
- 2011
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Ingår i: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 33:3, s. 638-643
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Tidskriftsartikel (refereegranskat)abstract
- Biocomposites derived from polymeric resin and lignocellulosic fibers may be processed at temperatures ranging from 100 degrees C to 230 degrees C for durations of up to 30 min. These processing parameters normally lead to the degradation of the fiber's mechanical properties such as Young's modulus (E), ultimate tensile strength (UTS) and percentage elongation at break (%EB). In this study, the effect of processing temperature and duration of heating on the mechanical properties of coir fibers were examined by heating the fibers in an oven at 150 degrees C and 200 degrees C for 10,20 and 30 min to simulate processing conditions. Degradation of mechanical properties was evaluated based on the tensile properties. It was observed that the UTS and %EB of heat treated fibers decreased by 1.17-44.00% and 15.28-81.93%, respectively, compared to untreated fibers. However, the stiffness or E of the fibers increased by 6.3-25.0%. Infra red spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were used to elucidate further the influence of chemical, thermal and microstructural degradation on the resulting tensile properties of the fibers. The main chemical changes observed at 2922, 2851, 1733, 1651, 1460, 1421 and 1370 cm(-1) absorption bands were attributed to oxidation, dehydration and depolymerization as well as volatization of the fiber components. These phenomena were also attributed to in the TGA, and in addition the TGA showed increased thermal stability of the heat treated coir fibers with reference to the untreated counterparts which was most probably due to increased recrystallization and cross linking. The microstructural features including microcracks, micropores, collapsed microfibrils and sort of cooled molten liquid observed on the surface of heat treated coir fibers from the scanning electron microscope (SEM) could not directly be linked to the effect of temperature and durations of heating although such features may have largely account for the lower tensile properties of heat treated coir fibers with reference to untreated ones.
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| 2. |
- Ndazi, Bwire, et al.
(författare)
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Characterization of the potential of soda cooking to extract fibrous residues from rice hulls
- 2010
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 1:3, s. 143-160
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, the potential of soda cooking to extract fibrous residues from rice hulls was investigated. Soda cooking was carried out at 170oC for 60 minutes using 5 to 13% NaOH. The goal was to selectively degrade silica and lignin from the structure of the rice hulls and produce fibrous carbohydrates that could be used as fillers in polymer biocomposites. This was studied by characterizing the physical and chemical properties of the fibrous residues and the spent liquor products. Results of scanning electron microscopy have revealed a substantial fragmentation of rice hulls above 7.5% NaOH charge. The fragmentation was accompanied with a significant removal of silica and lignin and the reduction of fibrous residues yield to 57% at 13%NaOH. Wet chemical composition analyses, infrared spectroscopy and x-ray spectroscopy have also revealed that lignin and silica were partly retained in the fibrous residue while the carbohydrates content were not affected. It is therefore concluded that soda cooking could be among the best processes for dissolving lignin and silica from rice hulls if the cooking conditions are optimized
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| 3. |
- Ndazi, Bwire Sturmius, et al.
(författare)
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Characterization of hydrolytic degradation of polylactic acid/rice hulls composites in water at different temperatures
- 2011
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Ingår i: Express Polymer Letters. - : Department of Polymer Engineering, Scientific Society of Mechanical Engineering. - 1788-618X. ; 5:2, s. 119-131
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Tidskriftsartikel (refereegranskat)abstract
- Hydrolytic degradations of polyactic acid/rice hulls (PLA/RH) composites with various rice hulls contents due to water absorptions at 23, 51 and 69 degrees C were investigated by studying the thermal properties, chemical composition, molecular weight, and morphology of the degraded products. The results have attested that the stability of PLA/RH composites in water depends slightly on rice hulls contents but it is significantly influenced by water temperature. Water adsorption in 30 days at 23 degrees C was between 0.87 and 9.25% depending on rice hull contents. However, at thermophilic temperatures, the water adsorption and degradation of these products were increased significantly. Saturations were achieved in less than 25 and 9 days at 51 degrees C and 69 degrees C, respectively, while hydrolytic degradation was demonstrated by an increase in fragility and development of crystallinity. At 69 degrees C, there were significant reductions of the decomposition and glass transition temperatures of the polymer by 13 degrees C. These changes were associated with the reduction of the molecular weight of PLA from 153.1 kDa to similar to 10.7 kDa due to hydrolysis of its ester group.
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