Browsing by Author "Nyahumwa, C."
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Item Compressibility and Stress Relaxation Characteristics of Rice Husks(University of Witwatersrand, 2003-12) Ndazi, Bwire S.; Nyahumwa, C.; Tesha, J. VItem Effect of Rice Husks Modifications on Water Absorption Resistance of Rice Husk Based Panels(2006-10) Ndazi, Bwire S.; Tesha, J. V; Nyahumwa, C.; Karlssion, SItem Effect of Temperature and Durations of Heating on Coir Fibers(Industrial Crops and Products, 2011) Ezekiel, N.; Ndazi, Bwire S.; Nyahumwa, C.; Karlsson, S.Biocomposites derived from polymeric resin and lignocellulosic fibers may be processed at temperatures ranging from 100 ◦C to 230 ◦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 ◦C and 200 ◦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 and1370 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.Item Effectiveness of Steam and Alkali Treatments of Rice Husks on the Mechanical Properties of Particleboards(2005-10) Ndazi, Bwire S.; Nyahumwa, C.; Tesha, J. V; Karlssion, S.Item Effects of steam curing and alkali treatment on properties on properties of rice husks(Pontifical University of Catholic, 2005) Ndazi, Bwire S.; Nyahumwa, C.; Tesha, J.; Karlssion, S.Item Mechanical Properties of Thermally Exposed Coir Fibres(2009-12-18) Ndazi, Bwire S.; Ezekiel, N.; Nyahumwa, C.; Karlssion, S.Item Optimization of the Pressing Conditions for Manufacture of Rice Husks-TF and PF-Bonded Particleboards(2007) Ndazi, Bwire S.; Tesha, J.; Nyahumwa, C.Item Properties and Performance of Treated Rice Husks in the Composite Panel(University of Dar es Salaam, 2014-07) Ndazi, Bwire S.; Nyahumwa, C.; Tesha, J. V; Karlssion, S.