Browsing by Author "Kawira, Millien"

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    Characterization of composite material from the copolymerized polyphenolic matrix with treated cassava peels starch
    (Heliyon, 2020-07) Kariuki, Stephen W.; Wachira, Jackson M.; Kawira, Millien; Murithi, Genson L.; Marangu, Joseph M.
    Conventional binders in the particleboards formulation involve use of formaldehyde resins. Epidemiologic studies show that formaldehyde is carcinogenic. Efforts to reduce formaldehyde emissions by use of scavengers has not been proven to reduce the emission. Molecular bonding of biobased adhesive molecules with lignocellulose materials provides an alternative way of producing composite material. In this study, maize stalk (MS), rice husks (RH) and sugarcane bagasse (SB) were used as sources of lignocellulose materials for particleboard formulation. SB, MS and RH were collected from their respective sites, sorted and dried. MS and RH were ground. Lignin content determination was done by drying lignocellulose material at 105 C. Lignocellulose materials were prepared by hydrolysis of dried lignocellulose material with sodium hydroxide. Oxidized starch was prepared by oxidation of cassava peel starch using alkaline hydrogen peroxide. Particleboards were formulated through starchlignocellulose polymerization at 60 C compressed with 6.5 Nmm 2 pressure. Characterization of raw materials and formulated particleboards was done using XRD for mineralogical analysis, FTIR and NMR for elucidation of functional groups transformation. The results showed that esterification is the main process of chemical bonding in the particleboard formulation due to reaction between COOH from starch and and OH- from lignocellulose. Etherification between hydroxyl groups from starch with hydroxyl groups from lignocellulose material. RH combined more through silication process with cassava peels starch than RH and SB showing materials containing high cellulose and hemicellulose content are more compatible. Composite materials formulated were used to produce medium density particleboards that can be used for making furniture and room partitioning.
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    Characterization of Local Nano-Heat Transfer Fluids for Solar Thermal Collection
    (Hindawi, 2020-08) Kawira, Millien
    Performance of organic oils in solar thermal collection is limited due to their low thermal conductivity when they are compared to molten salt solutions. Extraction of organic oils from plants can be locally achieved. 'e purpose of this study was to investigate the effect of use of copper nanoparticles in some base local heat transfer fluids (HTFs). Addition of volume fraction of 1.2% of the copper nanoparticles to oil-based heat transfer fluids improved their thermal conductivity as deduced from the thermal heat they conducted from solar radiation. 'e oil-based copper nanofluids were obtained by preparation of a colloidal solution of the nanoparticles. Impurities were added to increase the boiling point of the nano-heat transfer fluids. Stabilizers were used to keep the particles suspended in the oil-based fluids. 'e power output of the oil-based copper nano-heat transfer fluids was in the range of 475.4 W to 1130 W. 'e heat capacity of the steam in the heat exchanger was 93.7% dry and had a thermal capacity of 5.71 × 10 3 to 89.1 Js kJ. 'e heat rate of flow of the oil-based copper nano-heat transfer fluids was an average of 72.7 Js −1 −1 ·kg −1 −1 . 'e thermal efficiency for the oil-based copper nano-heat transfer fluids ranged from 0.85 to 0.91. 'e average solar thermal solar intensity was in the range 700 Wm ·kg . 'e heat exchanger used in this study was operating at 4.15 × 10 −2 −2 to 1180 Wm 3 kJ and a temperature of 500.0 ° C. 'e heat transfer fluids entered the exchanger at an average temperature of 381 ° C and exited at 96.3 ° C. 'e average temperatures of operation ranged between 394.1 C and their heat coefficient ranged between 290.1 Wm −2 ° −2 ° C and 254.1 Wm ° C and 219.7 ° C with respective temperature efficiencies ranging between 93.4% and 64.4%. It was established that utilization of copper nanoparticles to enhance heat transfer in oil-based local heat transfer fluids can mitigate energy demand for meeting the world’s increasing energy uses, especially for areas inaccessible due to poor land terrain.
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    Characterization of Prototype Formulated Particleboards from Agroindustrial Lignocellulose Biomass Bonded with Chemically Modified Cassava Peel Starch
    (Hindawi, 2019) Kariuki, Stephen Warui; Wachira, Jackson M.; Kawira, Millien; Murithi, Genson Leonard
    Conventional methods of making particleboards utilize wood chips. +is has resulted in a decrease in the tree cover due to the increase in wood demand. +e effect has been climatic change. Wood is bound using phenol formaldehyde resin. Because of the decrease in the forest cover, alternative lignocellulose materials are required. In this study, lignocellulose materials used include sugarcane bagasse, maize stock, and rice husks. +e cassava-starch mix with borax was used as a binder in particleboard formulation. +e lignin content was determined, and its effect on properties of boards was investigated. +e resultant composite material was molded at a pressure of 6.5N/mm2 and at 30°C. +e resultant particleboards had mean densities ranging from 0.604 to 0.611 g/cm3. +e modulus of elasticity ranged from 2364.2N/mm2 to 3329.93N/mm2, modulus of rupture ranged from 13.55N/mm2 to 14.83 N/ mm2, and internal bonding ranged from 1.613N/mm2 to 2.370N/mm2. +e performance of the board was dependent on the lignocellulose material used. Fourier transform infrared spectroscopy analysis showed that main chemical bonding in the particleboard resulted from esterification of –COOHfrom lignocellulose and OH- from starch.+e particleboards formulated were found to be of low-density-fibre standard used in a similar manner to the conventional low-density particleboards
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    Crop residues used as lignocellulose materials for particleboards formulation
    (Heliyon, 2020-09) Kariuki, Stephen W.; Wachira, Jackson M.; Kawira, Millien; Murithi, Genson L.
    Efforts to reduce pressure on use of wood in particleboard formulation have included the use of non-wood materials such as crop residues. Physical and mechanical properties are determined by the number of the hydroxyl (-OH) groups. Hydroxyl (-OH) groups attracts water molecules through hydrogen bonding affecting water absorption (WA) and thickness swelling (TS). WA and TS affect curing process of adhesive. Curing process of adhesives affects the mechanical characteristics of formulated particleboards. These challenges have been acted upon continuously through research. This review paper presents crop residues used as alternative lignocellulose material source in particleboard formulation and the various advances that have been made to improve on the properties of the resultant particleboards. Improvement over time of the non-wood material in composite materials focusses on increasing water resistance and compatibility between lignocellulose and binder. Crop residues-based are used in making medium and low density particleboards. These boards have shown good mechanical characteristics which include modulus of rupture (MOR), modulus of elasticity (MOE) and internal bonding (IB). MOR, MOE and IB have over time been improved by enhancing chemical compatibility of lignocellulose material and the binders. Water absorption and thickness swelling remain challenge. This review paper further explored various methods of improving water absorption and thickness swelling of crop-residue based particleboards
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    Formaldehyde Use and Alternative Biobased Binders for Particleboard Formulation: A Review
    (Hindawi, 2019-10) Kariuki, Stephen Warui; Wachira, Jackson M.; Kawira, Millien; Murithi, Genson Leonard