Papers by Author: Duangdao Aht-Ong

Abstract: Bacterial nanocellulose (BNC) is a natural polymer gel with unique properties that are suitable for developing advanced film applications such as edible coating and packaging. However, transforming BNC gel into a suspension and applying it as a film still lacks knowledge of the condition and method since BNC film performance depends on many parameters caused by the transformation process. This work studied two important primary variables, the number of homogenization cycles and the BNC concentrations, for transforming BNC gel into aqueous suspension using a microfluidizer to homogenize nanofibers and water medium. The BNC films obtained from the suspensions were examined for their properties, i.e., morphology, crystallinity index, optical, thermal, and mechanical properties. The results explored that the number of homogenization cycles had a non-significant impact on the characteristics and properties of BNC suspension and film. A significant improvement in film properties was found when using a higher BNC concentration at 1% w/v compared with 0.5% w/v at the equivalent number of homogenization cycles (40 cycles). The degradation temperature of this film increased by 13%, and Young’s modulus and tensile strength increased more than twice compared with the 0.5% w/v sample, increasing from 0.3 to 0.7 MPa and from 9 to 19 kPa, respectively. This finding would benefit the further development of BNC film for coating and packaging applications.

Abstract: Moringa oleifera Lam. leaves is the popular plant which provides an impressive range of medicinal uses because of major phytoconstituents in leaves. Such phytoconstituents contents are highly affected by extraction conditions. Therefore, the effects of different solvent extraction, temperature and time of extraction on antibacterial activity and total phenolic contents (TPC) of M.oleifera Lam. leaves extract were determined. The antibacterial result of all extract against E.coli showed no inhibition zone, while ethanolic extracts significantly affected to S.aureus inhibition that increasing concentration of ethanol provided an increasing in inhibition zone and decreasing MIC value from 5 to 1.25 mg/ml. Low-temperature extraction (40°C) was indicated as the optimum temperature which led to high antibacterial activity. The effect of extraction time was directly related to the inhibition zone. The highest inhibition zone and MIC value were obtained from extract which was extracted by using 70%MeoH, 40^OC and 3 h. TPC result revealed a significant relationship with antibacterial activity, meaning that higher TPC led to higher antibacterial inhibition.

Abstract: This work was focused on the effects of filler concentration on the antibacterial activity and biodegradable behavior of poly (butylene succinate) (PBS) composite films containing silver exchanged zeolite ZSM-5 (SZSM-5). The composite films were prepared by chill roll cast film extrusion, by varying the silver zeolite content from 0.5 to 4 %wt. The silver content in zeolite was examined by energy dispersive X-ray spectroscopy (EDX). The morphology and crystal structure of silver zeolite were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) technique, respectively. The incorporation of silver did not influence the zeolite morphology and its crystal structure. The antibacterial action of composite films was investigated against gram-negative Escherichia coli and gram-positive Staphylococcus aureus. The results revealed that the PBS composite films containing SZSM-5 showed 99.9% of bacterial reduction. The optimal SZSM-5 content in PBS composite films was 0.5%wt because it was the lowest concentration that showed high efficiency of antibacterial behavior. In case of biodegradable ability, PBS composite films incorporated with 0.5%wt of SZSM-5 exhibited the degradation after three-month of soil burial test, although they exhibited slower rate than neat PBS films. The SEM micrographs of the films after soil burial test displayed the cavity on film surface, indicating the biodegradable properties of the films. PBS composite films incorporated with 0.5%wt of SZSM-5 showed the potential to be used as the food packaging.

Abstract: In this work, we described an effective approach to prepare nanofibrillated cellulose (NFC) with cellulose II structure under mild condition. Firstly, the water hyacinth (WH) was subjected to a series of a two-step chemical treatment, NaOH/urea pretreatment, and mechanical defibrillation at different defibrillation times. After that, raw water hyacinth fiber (RWF), bleached water hyacinth fiber (BWF), NaOH/urea pretreated water hyacinth fiber (PWF), and the resulting NFC were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) as well as rheological measurements. It was found that RWF and BWF exhibited cellulose I crystal structure, whereas PWF and the obtained NFC possessed cellulose II crystal structure. FTIR analysis confirmed the evidence that no other chemical reactions preferentially occurred during both NaOH/urea pretreatment and mechanical defibrillation. As evidenced by rheological properties analysis, the NFC aqueous suspension with a gel-like structure demonstrated a shear-thinning behavior. The obtained NFC could potentially be utilized as a reinforcement for polymeric composites.

Abstract: Surface treated parawood microcrystalline cellulose (PW-MCC) performed under mechanochemical reaction using planetary ball milling at ambient temperature was used as a reinforcing material in polypropylene composites. Initially, PW-MCC was prepared by acid hydrolysis of parawood sawdust pulp. After that, PW-MCC was treated with vinyltrimethoxysilane at milling speed 400 rpm for 60 min. The surface composition from XPS indicated the existence of silicon atom on silane-treated PW-MCC. The thermal stability of PW-MCC was also improved and SEM micrograph revealed rough surface after modification reaction. The untreated PW-MCC and treated PW-MCC were applied to prepare polypropylene composites at 5-30 wt% loading content without a compatibilizer. The results demonstrated that silane-treated PW-MCC/PP composites enhanced tensile strength, thermal stability and water resistance of the composites.

Abstract: Banana is one of the most important tropical fruits in Thailand. It is available throughout the year, i.e., no specific growing season, resulting to the low cost. All parts of banana plant can be used, particularly its fruit has several adaptable in term of how to eat it. However, banana is ripe and perishable easily. Therefore, it is a potential resource that can be utilized and developed in order to add more value to this raw material. In this work, green banana fruits were used as a raw material for preparing a starch nanocrystal reinforcing filler in bio-nanocomposites. The green banana was extracted into banana starch by using 0.05 N sodium hydroxide solution. The composition of the obtained banana starch contained 90.61% of starch, 18.82% of amylose, 0.19% of protein, 0.11% of ash, and 0.03% of lipid. The banana starch composition exhibited low content of protein, ash, and lipid (<0.5%) indicating that the obtained banana starch was pure enough to be used. After that, starch nanocrystal (SNC) was prepared from banana starch by acid hydrolysis with 3.5 M sulfuric acid and 3.0 M hydrochloric acid at 40^°C for 7 and 5 hours, repectively. The obtained banana SNC showed an increase in the degree of crystallinity from 28.03% for native banana starch to 47.13% and 40.15% for banana SNC prepared from sulfuric and hydrochloric acid hydrolysis, respectively. Furthermore, the thermal properties of banana SNC were investigated by differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA) in order to assess thermal stability of banana SNC for using as reinforcing filler in bio-nanocomposite. The decomposition temperature of native banana starch and SNC was in the range of 260-315°C. The gelatinization temperature of banana SNC increased as a result of the increment of its degree of crystallinity when comparing with native starch.

Abstract: Biodegradable blend films of polylactide (PLA), thermoplastic starch (TPS), and poly(butylene adipate-co-terephthalate) (PBAT) were prepared through reactive modification. Three types of compatibilizers, methylenediphenyl diisocyanate (MDI), maleic anhydride (MA), and MA-g-PE, were studied. PLA and PBAT were blended in the presence of the compatibilizer to improve and evaluate the interfacial interaction. PBAT content was varied from 0 to 20 wt%, while compatibilizer content was differed from 0 to 5 wt% based on PBAT amount. For ternary blending, PLA, TPS, and PBAT were melt-blended with and without compatibilizer in a twin screw extruder using glycerol and tapioca starch as plasticizer and filler, respectively. The effects of type and content of compatibilizer and blend compositions on the physical, thermal, morphological, and tensile properties of the films were investigated. The results showed that the blend films with MDI had appropriate physical, thermal, and tensile properties. The presence of small amount of MDI enhanced the thermal and tensile properties of the films compared to the uncompatibilized films. This can be explained by a uniform morphology of the dispersed phase in the PLA matrix.

Abstract: This work focused on the preparation of the biocomposite films of polylactic acid (PLA) reinforced with microcrystalline cellulose (MCC) prepared from agricultural waste, banana stem fiber, and commercial microcrystalline cellulose, Avicel PH 101. Banana stem microcrystalline cellulose (BS MCC) was prepared by three steps, delignification, bleaching, and acid hydrolysis. PLA and two types of MCC were processed using twin screw extruder and fabricated into film by a compression molding. The mechanical and crystalline behaviors of the biocomopsite films were investigated as a function of type and amount of MCC. The tensile strength and Young’s modulus of PLA composites were increased when concentration of MCC increased. Particularly, banana stem (BS MCC) can enhance tensile strength and Young’s modulus of PLA composites than the commercial MCC (Avicel PH 101) because BS MCC had better dispersion in PLA matrix than Avicel PH 101. This result was confirmed by SEM image of fractured surface of PLA composites. In addition, XRD patterns of BS MCC/PLA composites exhibited higher crystalline peak than that of Avicel PH 101/PLA composites

Abstract: This work involved a study of polymer-fiber composites as biodegradable packaging made from recycled polyethylene (r-PE) and chemical-treated cotton fabric waste micro fibers. A compatibilizer, polyethylene-graft-maleic anhydride (PE-g-MA), was used to improve properties of the composites. Factors affecting composite properties were investigated including % PE-g-MA loading, and % fiber loading. The fiber composites were prepared by melt-blending technique. The materials were first mixed by a twin-screw extruder and shaped into samples by an extrusion blow molding machine. The samples were then characterized for mechanical, and morphological properties. It was found that properties of the composites were improved by adding the compatibilizer. Optimum properties of the composites were found at 10% (wt%) PE-g-MA loading. It was also revealed that tensile strength and modulus was found to increase as the % fiber loading was increased. SEM micrographs confirmed that interfacial bonding between the cellulose fibers and the r-PE matrix was enhanced as fewer voids at the interfaces were revealed by adding the PE-g-MA compatibilizer to the composites. Film formation occurred on all composites even if the polymer itself was inert biodegradation. The microbial colonization affected mainly of surface properties r-PE composites while changes were monitored also in the bulk properties of cellulose microfiber.

Abstract: The release of ethylene gas from agricultural products such as fruits, vegetables, and flowers during storage and transportation is the main cause of blooming of flowers and ripeness of fruits before their ripening phase. The ethylene gas acts as hormone plant leading to a decrease in the life time of agricultural products and a deterioration of product value. The continuous development of ethylene gas sensor is needed to increase an efficiency in detection and indicating life time cycle of agricultural products. The aims of this research were to fabricate ethylene gas sensor based on polyaniline/multiwall carbon nanotube (PANi/MWCNT) composites and to investigate the effect of MWCNT content on an improvement of its sensitivity. The sensitive layer for ethylene sensor was electrochemically synthesized from aniline in acid aqueous solution with different amounts of MWCNT. With cyclic voltammetry method, the sensitive layer of PANi/MWCNT was electrochemically synthesized via an in situ radical polymerization by repeating potential cycling in the range of -0.3 to 1.0 V relative to the silver reference electrode and platinum counter electrode. The response of these composite films for ethylene gas was evaluated by monitoring the change in electrical resistance at room temperature. After three month aging, the results revealed that the PANi/MWCNT composite films had higher response than pure PANi film and can be responded ethylene gas as lower as 10 ppm. The PANi/MWCNT composite films were characterized by fourier transform raman spectroscopy (FT-RAMAN). Thermal behaviors of PANi-MWCNT composite films were investigated by thermogravimetric analyzer (TGA). The morphology of PANi/MWCNT composite films were investigated by scanning electron microscope (SEM).