Browsing by Author "Tesha, J. V."

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Chemical and Physical Modifications of Rice Husks for Use as Composite Panels
    (Composite, 2007) Ndazi, Bwire S.; Karlssion, S.; Tesha, J. V.; Nyahumwa, C. W.
    Modifications of rice husks surfaces by steam and sodium hydroxide (NaOH) were carried out in order to study the effects of these on the surface functional groups properties and performances of the composite panels bonded with phenol formaldehyde (PF) resin. Comparison was made between untreated and ground rice husks. The removal of carbonyl and silica groups as observed by ATR-FTIR improved the rice husk-resin interfacial bonding as revealed by an increase in the modulus of elasticity to 2.76 ± 0.28 GPa, which is above the minimum value of 2.1 GPa recommended in EN 312-3 standard. On the other hand, steam treatment did not lead to any change in the outer surface chemical functional groups. Still, an increase in the mechanical properties of the composite with increase in steam temperature was observed. This showed that other mechanisms than changes in the surface chemical groups led to improved mechanical properties. TGA thermographs of unmodified and NaOH treated rice husks indicated that untreated rice husks exhibited higher thermal stability compared to rice husks treated with NaOH. The decrease in thermal stability of NaOH treated rice husks is an indication of possible degradation of rice husks by the concentrated NaOH used. This study has shown that the use of complementary testing techniques provides useful structure–property relationship in the understanding of the performance of materials.
  • Thumbnail Image
    Item
    . Chemical and Thermal Stability of Rice Husks against Alkali Treatment
    (Bioresources, 2008) Ndazi, Bwire S.; Tesha, J. V.; Nyahumwa, C. W.
  • Thumbnail Image
    Item
    Production of Rice Husks Composites with Acacia Mimosa Based Tannin Resin
    (Journal of Materials Science, 2006) Ndazi, Bwire S.; Tesha, J. V.; Karlssion, S.; Bisanda, Elias T. N.
    Rice husks are amongst the typical agricultural residues, which are easily available in huge amounts. They have been considered as raw material for composites panels’ production. However, the major hindrance in rice husks utilization for composite manufacture lies in the lack of direct interaction with most adhesive binders to form the anticipated interfacial bonds. Rice husks are highly siliceous and have poor resistance to alkaline and acidic conditions. Manufacture of rice husks composites panels having good interface bond is difficult and largely dependent on a proper understanding of the interaction between the husks and the binder. This paper presents and discusses results on the production of composites boards from a mixture of rice husks and wattle (Acacia mimosa) tannin based resin. The experimental results have shown that the ‘as received rice husks’ when blended with alkali-catalyzed tannin resin do not result in optimum composite panel properties. However, it was found that a slight physical modification of the rice husk particles by hammer-milling resulted in drastic improvements in the interfacial bond strength and stiffness of the composites panels from 0.041 MPa to 0.200 MPa and 1039 MPa to 1527 MPa, respectively.
  • Thumbnail Image
    Item
    Properties of Rice Husk Particleboards Bonded by Tannin Based Resin
    (Uhandisi Journal, 2002) Ndazi, Bwire S.; Tesha, J. V.; Bisanda, Elias T. N.; Karlssion, S.
  • Thumbnail Image
    Item
    Some Opportunities and challenges of producing bio-composites from non-wood residues
    (Journal of Materials Science, 2006) Ndazi, Bwire S.; Tesha, J. V.; Bisanda, Elias T. N.
    Plant-based composites (bio-composites) may in the future, become materials to replace polymer based composites and wood in terms of their attractive specific properties, lower cost, simple processing technologies, eco-friendliness, and ability to be recycled after use. The quality and performance of plant fibre-based composites can further be improved by adopting appropriate engineering techniques. Although plant-based fibres have these advantages, they also have some limitations. One of the serious problems of plant fibres is their strong polar character, which creates many problems of incompatibility with most thermosetting and thermoplastic matrices. Production of bio-composites with high quality and performance is therefore based on adjusting the properties of the constituents to meet the requirements of the composite material i.e. a product with consistent, uniform, predictable, and reproducible properties. Such adjustments involve creating strong interfacial bonds between the lignocellulosic substrates and the binder. Successful development of biocomposites therefore stem from a careful understanding of the influence of these adjustments on the composite properties. This paper suggests some opportunities available in producing bio-composites from non-wood resources, and the challenges that must be overcome to make this technology commercially viable. Gaps in knowledge and information required before full commercialisation of these materials are identified.