Theses & Dissertations

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https://hdl.handle.net/20.500.14170/194

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Now showing 1 - 5 of 213
  • Publication
    Preparation, chemical modification and degradability of durian seed starch (DSS) based composites
    ( 2018)
    Noor Marlyna Ismail
    Preparation, chemical modification and degradability of Durian Seed Starch (DSS)/low-density polyethylene (LDPE) composites were investigated. All of composites were prepared using Brabender Plastograph EC internal mixer at temperature of 150 ͦC and rotor speed of 50 rpm, and moulded using compression moulding at temperature of 150 ͦ C. Particle size analysis revealed that average size of DSS used in this research is 15 μm. Scanning electron microscopy (SEM) of unmodified and modified starch were found to be irregular shape particles and shows agglomeration pattern. The Fourier Transform Infra-Red (FTIR) analysis on modified DSS indicates that the modification is easily detected due to the new positions of absorbance peaks. The effect of filler loading and different types of chemical modifications on mechanical properties, morphology and thermal properties of LDPE/DSS composites were studied. The various types of chemical modifications via acetic acid (AAc), acrylic acid (AA) and lactic acid (LA) were chosen in this study. The results showed that the addition of starch into LDPE matrix reduced the tensile strength, elongation at break, degree of crystallinity (Xc), whereas the thermal stability, Young’s modulus and percent of degradability of composites increased. The chemical modification of DSS resulted positive effect on mechanical and thermal properties of LDPE/DSS composites. The modified LDPE/DSS composites with AAc and AA have higher tensile strength, Young’s modulus, thermal stability, degree of crystalinity (Xc) compared to unmodified LDPE/DSS composites. Improvement in interaction between modified DSS and LDPE matrix was proven by SEM study. The FTIR spectra of modified DSS showed the new functional group from the formation of chemical bonding between DSS and chemical modifying agent. The modified LDPE/DSS composites with LA had lower tensile strength and elongation at break, but higher Young’s modulus, thermal stability, Xc than modified LDPE/DSS composites with AAc and AA. The SEM micrographs of modified LDPE/DSS composites with LA exhibit a rough surface. The composites properties were further enhanced with incorporation of montmorilonite (MMT) and Kaolin, as hybrid filler into DSS. The DSS/MMT and DSS/K hybrid ratio is studied at 100/0/0, 94/5/1, 88/10/2, 82/15/3 and 76/20/4 weight percent (wt %). Both hybrid fillers were found to act as reinforcing fillers to the DSS, with for the MMT show better properties than Kaolin. Both additions of hybrid fillers also have improved the tensile properties as well as the thermal degradation properties of the composites. SEM was also done to investigate the fracture surface behavior. Simple biodegradability test was conducted on each series of the composites were taken for 9 month. Based on biodegradability test, the modified LDPE/DSS composites with AAc had higher rate of degradation compare to AA and LA. Meanwhile, hybrid filler of MMT give higher degradability compare hybrid filler of Kaolin. FTIR analysis and optical microscopy was done to determine the degradability of the composites.
  • Publication
    Properties of Polyvinyl alcohol composite film reinforced with nanocellulose isolated from coconut husks fiber
    ( 2021)
    Nurdiana Othman
    Coconut husks is an agro-industrial waste available in large quantities in several countries, including Malaysia. This research utilizes the waste of coconut husks as a source of cellulose to obtain cellulose nanocrystals (CNCs) via acid hydrolysis process. The box-behnken design (BBD) based on the response surface methodology (RSM) was applied to study the effects of sulphuric acid concentration, reaction temperature and reaction time on the yield of CNCs and the regression model was established between the yield and three factors. The results showed that the yield of the CNCs was 44.84%, under the optimum conditions of 64.61% of sulphuric acid concentration, 44.6 °C of reaction temperature and 58.54 min of reaction time. The CNCs presented a needle-shaped morphology, high crystallinity (63.5%), average length (L) of 92.84 nm, diameter (D) of 7.90 nm, and high aspect ratio (L/D) of 12. The effect of incorporating CNCs from coconut husks into the tensile strength, thermal and weight loss of polyvinyl alcohol (PVOH) to form biodegradable nanocomposites film were evaluated. PVOH/CNCs nanocomposite films with different CNCs contents (1, 3, 5, 7 and 9% by wt) were prepared by solution casting method. The crystallinity index, tensile strength, thermal stability (TS), of the nanocomposites were measured. When compared to PVOH (0) film, the tensile strength of the nanocomposites improved significantly, by 35.7%. Based on the thermogravimetric analysis, the incorporation of CNCs into PVOH had improved the thermal stability of nanocomposite films. The biodegradability of PVOH/CNCs nanocomposites film was also measured after the films were introduced to the soil burial method for 10 weeks. The addition of CNCs into PVOH matrix had enhanced the weight loss of nanocomposite films and PVOH (9) showed the highest weight loss (23.1%) compared to the other contents of CNCs. The soil obtained on the surface of PVOH/CNCs were isolated using serial dilution technique. Then, the potential microorganisms of degrading plastic were investigated by solid state fermentation (SSF) and liquid state fermentation (LSF). The isolates bacterial (D1, D2, D3, D4 and D5) were cultured in mineral salt medium broth containing PVOH/CNCs film powder. The bacterial D1 showed the highest growth response (0.254) in broth media. The fungal S1 had contributed to the weight reduction weight of PVOH/CNCs nanocomposite film by 3.13% after 14 days of cultivation. The molecular analysis through polymerase chain reaction and DNA sequencing indicated that the bacterial D1 is Citrobacter freundii sp. and fungal S1 is Aspergillus japonicas sp. with 99% and 100% similarities, respectively. The novelty of the study found Aspergillus japonicas sp. and Citrobacter freundii sp. were the first reported as fungal and bacterial strain of PVOH/CNCs degrader found in the soil. Therefore, the fungi and bacteria isolated from soil have the capability in degrading PVOH/CNCs nanocomposite films.
  • Publication
    Mechanical, thermal and electrical properties of ABS Copper Zinc Ferrite polymer composites fabricated using 3D printer compositing technique
    ( 2020)
    Khairul Amali Hamzah
    This study aims to produce polymers that capable of thermally conductive but low electrical conductivity using new fabrication compositing technique of 3D printer. Acrylonitrile-butadiene-styrene (ABS) has been used as a matrix due to its versatility and widely used in many applications. For thermal conduction purposes, copper zinc ferrite (CuZnFe2O4) have been selected as filler due to their unique properties which can improve thermal conductivity but has low electrical conductivity. To fabricate this conductive polymer, a three-dimensional printer (3D printer) was used. Fabrication of composites using 3D printers is gaining attention due to their advantages. However, the main challenge of using 3D printers is the lack of mechanical strength of the printed part. Therefore, the addition of filler material and varying the printer setting may increase the mechanical strength of the printed material. Two settings were used in this study which are raster angles (0⁰, 45⁰ and 90⁰) and infill density (50%, 75% and 100%). New methods have been introduced to produce composite materials using this 3D printer, which is the distributing of filler during the printing process using powder dispenser. Small modification has been made on the printer by installing powder dispenser. The dispenser was operated at three different speeds which are low speed (1000 rpm), medium speed (1400 rpm) and high speed (1800 rpm) to obtain different dispensed amounts of filler. The percentage of dispensed filler was determined using TGA which give 8 wt% for low speed, 11 wt% for medium speed and 14 wt% for high speed. All test results show that the production of thermally conductive, but electrically insulative polymers can be made using 3D printers utilizing dispensed filler. The results showed an increase in tensile strength, percentage of elongation at break, Young's modulus and hardness of the specimens by 23%, 66%, 9% and 21% respectively when the specimens were printed using raster angles 0⁰. For specimens printed at 100% infill density showed an increase in tensile strength, Young's modulus and hardness values were 17%, 96% and 64%, respectively. There was a decrease in the percentage of elongation about 11% at 100% infill density. However, the raster angle and infill density do not show insignificantincrease in thermal and electrical conductivity of the printed material. Approximately 724% increase in thermal conductivity and a decade increment in electrical conductivity after addition with a 14 wt% filler. The increase in mechanical properties and dynamic mechanical properties also increased by 118% for tensile strength, 22% for Young's modulus and 342% for hardness value after addition of 14 wt% filler. No significant changes were noted in mechanical and dynamic mechanical properties when the stoichiometric of reinforcer is changed. However, a 63% increase in thermal conductivitywas found in specimens with a filler stoichiometry is increased from x = 0 to x=1.
  • Publication
    Growth rate and morphology studies of grey oyster mushroom (Pleurotus Pulmonarius) using Chlamydospore induction liquid spawn
    ( 2021)
    Chong Shi Fern
    Spawn preparation from chlamydospore which is produced through spore induction technique has become a potential and promising technique in grey oyster mushroom cultivation. How long that chlamydospore can survive in the induction media and ability to grow in a large scale production had raised questions and need to be studied. Hence, in this study, spore induction technique was used to induce chlamydospore from grey oyster mushroom and the effect of storage duration on chlamydospore growth rate in flask and bioreactor were investigated. It was found that chlamydospores inoculum stored at 4°C and ambience condition for 8 months was still able to grow mycelium with average mycelial dry weight at 0.3100g and 0.3075g respectively. Mycelium inoculum however able to store up to 4 months with average mycelial dry weight at 0.2555g only. Chlamydospores inocula stored for 1 to 7 months took 33 days for colonization completion and increased to 36 days in the next month and so on. The highest growth rate obtained was from 2month’s stored chlamydospore inoculum which was 0.9105cm day-1 compared to the highest growth rate obtained from mycelium inoculum which was only 0.8661cm day-1 only. For the total yield production, 2 month’s store chlamydospore inoculum had also observed the highest recorded as 431.00g. The highest specific growth rate was obtained from 5 month’s stored chlamydospore inoculum at 0.0088g hour-1 with shortest doubling time 78.75 hours when cultivated in bioreactor. While the slowest was obtained from 5 month’s stored mycelium inoculum with specific growth rate at 0.0069g hour-1 and longest doubling time of 100.43 hours. The sustainability of active mycelium biomass was verified with the analysis of glucose concentration in the media where sugar uptake was high for chlamydospore at 1 month’s and 5 month’s stored chlamydospore. For the three months cultivation period, a total of 430.74g and 422.35g were obtained for 1 month’s and 5 month’s storage period of chlamydospore respectively. This study proved that chlamydospore from grey oyster mushroom is a potential inoculum for long term storage and revival ability on large scale production
  • Publication
    Characterization and properties of stearic acid, titanate and zirconate modified dolomite/polypropylene composites
    ( 2019)
    Nik Nur Azza Nik Adik
    An increase in demand for the use of natural mineral filler polymer composites has attracted attention towards a greener environment and in reducing the processing and production cost of composites materials. In this study the effect of dolomite filler content and the effect of filler treatments on the mechanical, thermal and degradation behaviour of modified dolomite/polypropylene (PP/dolomite) composites were investigated. The first part of this study reported on the preliminary study on optimum ground dolomite properties. The raw dolomite was ground using various grinding time in order to obtain the optimum size of dolomite particle to be incorporated into the composites. The grinding process of 2h resulted in optimum grinding parameter with particle size 8.183m and maintained crystalline structure even after the intensive grinding operation in the planetary mill. Secondly, the PP/dolomite composites containing 0 – 25 wt.% of dolomite was prepared using Brabender internal mixer at temperature 180°C , rotor speed 60 rpm and compression moulding method. The addition of dolomite into the PP matrix decreased the tensile strength and elongation at break of the composites. The Young’s modulus increased due to the addition of dolomite particulate filler into the PP/dolomite composites. Thermogravimetric analysis (TGA) confirms that the addition of lower content of dolomite increased thermal stability of the composites. In the third part, the effect of stearic acid content as modifier on the surface treatment of PP/dolomite composites was studied. It was found that the dolomite has been successfully modified by the stearic acid observed through the fourier transform infrared (FTIR) and exhibited that the optimum stearic acid content has elevated the percentage of hydrophobicity and resulted in highest tensile strength, elongation at break, flexural properties and also thermal stability of the polymer composites. A better interfacial adhesion between the particulate dolomite and PP also was observed. This optimum stearic acid content obtained was then maintained in order to compare the effect of other modifiers which were titanate (LICA12) and zirconate (NZ12) as modifiers towards the mechanical, thermal and morphology behaviour of the composites. The addition of these modifiers has shown a significant improvement the tensile strength and Young’s modulus of the composites. The modified PP/dolomite composites showed slight improvement on tensile strength, impact strength and flexural properties. FTIR spectra proved the changes of functional group of modified dolomite and enhancement of interfacial adhesion respectively. The addition of nanosilica has marked an improvement in the impact strength of modified composites compared to unmodified ones, but on the other hands it lowers the thermal stability. The final part of this study focused on the effect of degradation by natural and accelerated weathering to the mechanical and physical properties of PP/dolomite and its hybrid nanocomposites. The composites of PP with modified dolomite sustain the tensile strength for both natural and accelerated weathering.