Browsing by Author "Olupot, Peter Wilberforce"
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Item Application of Response Surface Methodology for Optimizing Tensile Strength of Rice Husk Fiber-Reinforced Polylactic Acid Composites(MDPI, 2021) Yiga, Vianney Andrew; Lubwama, Michael; Olupot, Peter WilberforceFiller/fiber loading and surface modification significantly influence tensile properties of natural fiber-reinforced plastic composites. It is therefore pertinent that they are suitably selected in order to yield the optimum tensile properties. Fiber-reinforced PLA composites were prepared us-ing compression molding with Box-Behnken Design experimental design approach. Factors, namely clay filler loading (1−5 wt.%), rice husk fiber loading (10−30 wt.%), alkali concentration (0−4 wt.%), rice husk variety (K85, K98) and alkali type (NaOH, Mg(OH)2) were varied. ANOVA determined significance of the factors affecting composites’ tensile strength. ANOVA results revealed the re-duced cubic model as best fit for tensile strength response. The desirability function revealed that variable values leading to optimum tensile strength (33.67 MPa) were 4.97 wt.%, 11.16 wt.% and 3.99 wt.% for filler loading, fiber loading and alkali concentration, respectively.Item Assessment of the techno-economic viability of B10 synthesis from second-generation biodiesel feedstocks in Uganda(Taylor & Francis, 2023-12) Tibesigwa, Timothy; Olupot, Peter Wilberforce; Kirabira, John BaptistThis paper assessed the technical and economic viability of biodiesel production from Second-generation feedstocks native to East Africa, which included Castor, Croton, and Jatropha. Their oils were converted to biodiesel by transesterification and characterizations of B100 and B10 done following ASTM D6751. ASPEN Plus V11 was used in process simulation and profitability analysis. Oil yields obtained ranged from 29.5% to 35.6%. B100 and B10 properties conformed to ASTM D6751. The negative Net Present Values obtained render B100 and B10 production uneconomical unless incentivized. Sensitivity analyses showed that NPV varied with feedstock cost and biodiesel selling prices. This assessment established that though a B10 policy based on second-generation feedstocks is technically viable, interventions are needed to make it profitable in Uganda.Item Development of fiberreinforced polypropylene with NaOH pretreated rice and coffee husks as fillers: Mechanical and thermal properties(Journal of Thermoplastic Composite Materials, 2020) Andrew Yiga, Vianney; Page, Sinja; Lubwama, Michael; Epple, Stefan; Olupot, Peter Wilberforce; Bonten, ChristianIncorporation of agricultural wastes as fillers in fiber-reinforced plastics is gaining momentum in plastics engineering research. In this study, fiber-reinforced polypropylene (PP) with rice and coffee husks as filler material were developed. The effect of alkali (sodium hydroxide) pretreatment of the husks on mechanical and thermal properties of developed PP biocomposites was observed. Filler material loading was varied from 0% to 20% for rice husks and 0% to 10% for coffee husks. A twin-screw extruder was used for compounding the PP matrix with rice and coffee husk filler materials. Tensile strengths and percentage elongation results varied from 27.4 to 37.4 MPa and 2.4% to 70.3% (unmodified coffee husks), 31.1 to 37.4 MPa and 5% to 70.3% (unmodified rice husks), 30.7 to 37.4 MPa and 5.3% to 70.3% (modified coffee husks), and 30.7 to 37.4 MPa and 4.8% to 70.3% (modified rice husks). Young’s modulus ranged between 1656 and 2247.8 MPa for biocomposite PP samples with unmodified filler material. Young’s modulus ranged between 1740 and 2160 MPa after alkali treatment of the filler material. Charpy impact strengths ranged from 1.2 to 4 kJ/m2 and 3.1 to 19.6 kJ/m2 for samples containing unmodified and modified filler material, respectively. Thermogravimetric analysis showed that an increase in filler content resulted into delayed weight loss at high degradation temperatures. The results suggest that these developed fiber-reinforced plastics can be used in applications requiring high thermal stability and good mechanical properties.Item Effect of Alkaline Surface Modification and Carbonization on Biochemical Properties of Rice and Coffee Husks for Use in Briquettes and Fiber- Reinforced Plastics(Journal of Natural Fibers, 2019) Yiga, Vianney Andrew; Lubwama, Michael; Olupot, Peter WilberforceEffects of alkaline surface modification and carbonization on biochemical properties of selected rice and coffee husk varieties in Uganda were studied. Alkali pre-treatment was done by washing the husks in NaOH at a 15:1 liquor ratio. Pre-treatment is used in biomass conversion to overcome chemical and structural difficulties. Carbonization resulted in production of bio-char. Results showed increased cellulose contents for both the husks and their bio-chars after pre-treatment with NaOH solution. Lignin and hemi-cellulose compositions were reduced after pre-treatment in NaOH solution. Bio-chars for all rice husk varieties showed an increase in lignin content after carbonization. Lignin contents for Robusta coffee husks also increased after carbonization. Cellulose content in bio-chars of both rice and coffee husks reduced drastically after carbonization. A simple regression model relating bulk density and biochemical composition was developed at an accuracy of 70%. Alkaline surface modification and carbonization effects on biochemical properties are due to their impact on the non-cellulosic material and hydrophobicity, respectively, on the fibers.Item Effects of sawdust and adhesive type on the properties of rice husk particleboards(Results in Engineering, 2022) Olupot, Peter Wilberforce; Menya, Emmanuel; Lubwama, Festo; Ssekaluvu, Lawrence; Nabuuma, Betty; Wakatuntu, JoelThis study set out to investigate the effects of adhesive type, rice husk and sawdust proportions on the properties of composite particleboards. Specimens of 200 × 200 × 24 mm were made by blending 500 g of rice husks with each adhesive type at a mass ratio of 1:1. The rest of the specimens of similar dimensions were prepared with addition of sawdust in the range of 10–40 wt%, while maintaining the ratio of biomass particles to adhesive at 1:1. Three commercial synthetic adhesives Fevicol (FV), Ponal (PA) and woodfix (WF) were used. The particleadhesive mixtures were molded into a mat which was subsequently cold pressed at 10 MPa and left to dry in air. Density, water absorption (WA), linear expansion (LE), thickness swelling (TS), modulus of elasticity (MOE), modulus of rupture (MOR) and screw holding capacity of the specimens were evaluated. Adhesives were found to have over 42% solid content, with similar liquid constituents but in varying proportions. FTIR library search for the spectra of FV, PA and WF revealed correlations of 82.5%, 78.6% and 50.2%, respectively with polyvinylacetate. The developed boards had density 510–610 kg/m3, MOE 13–26 MPa, TS 9–31%, LE 3–7%. These properties suit them for furniture boards and sound proofing. The properties improved with increasing proportion of sawdust. FV and PA-bonded particleboards exhibited higher stability and strengths than WF-bonded particleboards due to higher concentrations of polyvinyl-acetate in the latter. Blending 40 wt% sawdust, 10 wt% rice husk with 50 wt% of either FV or PA showed better prospects.Item Flame retardancy and thermal stability of agricultural residue fiber-reinforced polylactic acid: A Review(Polymer Composites, 2021) Yiga, Vianney Andrew; Lubwama, Michael; Pagel, Sinja; Benz, Johannes; Olupot, Peter Wilberforce; Bonten, ChristianBiocomposites containing natural fibers and biopolymers are an ideal choice for developing substantially biodegradable materials for different applications. Polylactic acid is a biopolymer produced from renewable resources and has drawn numerous interest in packaging, electrical, and automotive application in recent years. However, its potential application in both electrical and automotive industries is limited by its flame retardancy and thermal properties. One way to offset this challenge has been to incorporate natural or synthetic flame retardants in polylactic acid (PLA). The aim of this article is to review the trends in research and development of composites based on agricultural fibers and PLA biopolymers over the past decade. This article highlights recent advances in the fields of flame retardancy and thermal stability of agricultural fiber-reinforced PLA. Typical fiber-reinforced PLA processing techniques are mentioned. Over 75% of the studies reported that incorporation of agricultural fibers resulted in enhanced flame retardancy and thermal stability of fiberreinforced PLA. These properties are further enhanced with surface modifications on the agricultural fibers prior to use as reinforcement in fiber-reinforced PLA. From this review it is clear that flame retardancy and thermal stability depends on the type and pretreatment method of the agricultural fibers used in developing fiber-reinforced PLA. Further research and development is encouraged on the enhancement of the flame retardancy properties of agricultural fiber-reinforced PLA, especially using agricultural fibers themselves as flame retardants as opposed to synthetic flame retardants that are typically used.Item Investigation On Char Residues And Mean Reactivity Of Compression Molded Rice And Coffee Husks Biochar Reinforced Polypropylene(In ASTFE Digital Library, 2020) Yiga, Vianney Andrew; Lubwama, Michael; Olupot, Peter WilberforceFiber-reinforced plastics have gained utilization in recent years for many applications because they are a cheaper alternative to the ordinary petroleum-derived materials. On the other hand, considerable amounts of agricultural wastes still lack enough utilization. In this study, bio-chars of husks from two rice and two coffee varieties in Uganda were utilized as fillers to reinforce polypropylene (PP) and thus develop fiber-reinforced plastics. Bio-char filler material was varied between 0 % and 20 %. The plastics were prepared via melt mixing followed by compression molding. Effects of bio-char content on the thermal stability of the developed plastics were studied by use of an Eltra Thermostep Thermogravimetric analyzer. Thermogravimetric analysis (TGA) results showed that inclusion of bio-char improved the thermal stability of the developed fiber-reinforced plastics. Maximum rate of weight loss ranged from -0.0414 %/min (for 15 % unmodified Wita-9 rice bio-char) to 0.0023 %/min (for pure PP), corresponding to respective peak temperatures of 680.8 °C and 604 °C respectively. Peak temperatures generally increased with increase in filler loading. It was found out by this study that incorporation of bio-char fiber material resulted in increased char residues. These residues tended to hinder combustion. The highest char residues (17.4 %) were obtained when PP was loaded with 15 % neutral Wita-9 rice husks bio-char. The highest mean reactivity attained was 6.1×10-5 %/minute/°C obtained when 10 % unmodified Pussa rice husks bio-char was used to reinforce PP.Item Optimization of roughing filtration unit for a handwashing wastewater recirculation point-of-use system(Water Science & Technology, 2022) Olupot, Peter Wilberforce; Menya, Emmanuel; Jjagwe, Joseph; Wakatuntu, Joel; Románc, Franz; Hensel, OliverA downward roughing filter unit consisting of silica sand as the filter medium was optimized for performance towards removal of turbidity and suspended solids from handwashing wastewater. Design-Expert software was employed to optimize media particle size, filter depth, and flowrate. Linear and quadratic models were found to best fit the responses of turbidity and suspended solids removal, respectively. Particle size and flow rate were the only parameters with significant effects on removal of turbidity and suspended solids. Optimal conditions were found to be media particle size 0.6 mm, filter depth 12 cm, and flow rate 0.3 Lmin 1, corresponding to removal efficiencies of 62 and 67% for turbidity and total suspended solids (TSS), respectively, as predicted by the model. Validation of model at optimal conditions resulted in turbidity and TSS removal of 55 and 53%, respectively. Additionally, removal efficiencies of the roughing filter towards apparent colour, true colour, biochemical oxygen demand (BOD5), and chemical oxygen demand (COD) from handwashing wastewater were 56, 20, 32, and 5%, respectively. Overall, although turbidity of filtered water was .50 NTU, the reduction achieved by roughing filtration is a significant step in enhancing the performance of water treatment processes downstream, including filtration and adsorption by slow sand filters and activated carbon, respectively.Item Optimization of tensile strength of PLA/clay/rice husk composites using Box‑Behnken design(Biomass Conversion and Biorefinery, 2021) Yiga, Vianney Andrew; Lubwama, Michael; Pagel, Sinja; Olupot, Peter Wilberforce; Benz, Johannes; Bonten, ChristianAbstract It is extremely important to save costs and time while enhancing accuracy in experimentation. However, no study has utilized response surface methodology (RSM) to obtain the effects of independent parameters on properties of PLA/clay/rice husk composites. This study focused on optimization of tensile strength of fiber-reinforced polylactic acid (PLA) composites. RSM using Box-Behnken design (BBD) was used to determine optimum blending parameters of the developed composites. Fiber-reinforced PLA composites were prepared using compression molding. Rice husk fiber and clay filler were used to enhance tensile properties of PLA. Five factors, namely, clay filler loading (1 − 5 wt.%), rice husk fiber loading (10 − 30 wt.%), alkali concentration (0 − 4 wt.%), rice husk variety (K85, K98), and alkali type (NaOH, Mg(OH)2) were varied with 68 individual experiments. Tensile tests were carried out according to ASTM D638 standards. ANOVA results revealed that the quadratic models best fit the tensile strength response, with filler loading and fiber loading factors as the most significant model terms. Interaction effects were more predominant than linear and quadratic effects. The developed models used to determine maximum tensile strengths of PLA/clay/rice husk composites were in close agreement with experimental findings (R2 values of 0.9635, 0.9624, 0.9789, and 0.9731 for NaOH-modified K85 rice husks, Mg(OH)2-modified K85 rice husks, NaOH-modified K98 rice husks, and Mg(OH)2-modified K98 rice husks respectively). Individual optimal conditions were used to predict maximum tensile strengths in each set of developed composites. The predicted tensile strengths were 32.09 MPa, 33.69 MPa, 32.47 MPa, and 32.75 MPa for PLA/clay composites loaded with NaOH-modified K85 rice husks, Mg(OH)2-modified K85 rice husks, NaOH-modified K98 rice husks, and Mg(OH)2-modified K98 rice husks, respectively, which were very close to the obtained experimental values of 31.73 MPa, 33.06 MPa, 32.02 MPa, and 31.86 MPa respectively.