Advanced Materials Research Vols. 93-94

Abstract: In-situ applications such as Microbial Enhanced Oil Recovery (MEOR) and remediation of contaminated sites demand production of biosurfactants in large quantities under oxygen limiting conditions. Few microorganisms have been isolated so far which can cater such need. In this paper, the characteristics of a biosurfactant produced under complete anaerobic conditions are presented. A novel biosurfactant producing microorganism, Pseudomonas sp ANBIOSURF-1 was isolated in our laboratory, from a microbial consortium enriched from municipal sewage sludge. The microorganism utilized vegetable oils and produced biosurfactant under complete anaerobic conditions. TLC tests revealed the presence of sugar and lipid as hydrophilic and hydrophobic moieties respectively. The biosurfactant synthesized under anaerobic condition thus belonged to class of glycolipids similar to that of rhamnolipids. The biosurfactant had a very low CMC value of 52 mg/l. The biosurfactant displayed good emulsifying activity over chlorinated solvents than the petroleum derivatives. The results suggest that Pseudomonas sp ANBIOSURF-1 could potentially be used for remediation of sites contaminated with chlorinated solvents through in-situ biosurfactant production.

Abstract: Titanium dioxide powder was prepared by a low temperature hydrothermal method. Titanium isopropoxide, ammonium hydroxide and nitric acid were used as the starting precursors. The mixed solution with final pH of 1 was treated in the autoclave hydrothermal at 80-100 °C for 2-4h. The phase of titanium dioxide powder was studied by X-ray diffraction (XRD). Anatase and rutile structure were obtained at 80 °C for 2-4h without calcination step. Anatase structure was obtained at 100 °C for 2-4h without calcination step. The morphology of titanium dioxide powder was investigated by scanning electron microscopy (SEM). The particle was irregular in shape and agglomerated with the range particle size of 0.5-0.8 µm. The chemical composition of titanium dioxide powder was examined by energy dispersive spectroscopy (EDS).The element chemical compositions show the characteristic X-ray energy level as follows: titanium Kα = 4.51 keV and Kβ = 4.93 keV and oxygen Kα = 0.52 keV, respectively.

Abstract: Epoxidized Natural rubber (ENR) with the epoxide content of 40 % was prepared and blended with various contents of chloroprene rubber (CR) and 50 phr of carbon black. The cure characteristic, mechanical properties and the effect of gasohol E-85 on the mechanical properties of the rubber vulcanizate were studied. It was revealed from cure characteristic results, tested by Moving Die Rheometer (MDR), that minimum torque of the rubber compounds increased with the content of CR whereas maximum torque tended to increase at the content of 10 phr and decrease after this content, of which the values agreed well with the modulus at 100% elongation in rubber vulcanizates. Considering characteristic scorch and cure time, the values increased with the CR contents. It was clear from the result that at the ENR:CR ratio of 90:10, modulus of 100% elongation and tear strength exhibited the highest values. It was also found that the mechanical properties of the blend vulcanizates were slightly suffered by gasohol E85 except for tear strength. It was understood that this must be because of the effect of the phase continuity and crosslinking that occurred differently in two phases. The phase morphology of the blends were also investigated and reported in the research.

Abstract: The solar light consists of ultraviolet, visible and infrared ray. The ultraviolet and infrared rays, unlike visible ray, are not benefit to photosynthesis. Inorganic ultraviolet absorbing materials are mostly in crystallised phase such as TiO2, ZnO and CeO2 which caused lower transmittion in visible range. As known that, the commercial organic UV absorbers can absorb only the appointed UV wavelength. TiO2 emulsion for ultraviolet blocking was synthesized in this project in order to overcome such poor transmittion behavior. The preparative TiO2 emulsion can absorb UV completely without interfering the visible light transmittance. This is because the synthesized TiO2 via emulsion method was mainly an amorphous phase. The obtained composite film containing amorphous phase of TiO2 shows 80-90% transmittance of the visible light, 20-70% absorbance of ultraviolet A and 70-95 % absorbance of ultraviolet B.

Abstract: Asphalt emulsion is manufactured by emulsification of asphalt, and it is an energy-saving, ecologically safe material because it does not need any heating processes which can emit gas and fire hazard in its use. The purpose of this study is to elucidate the feasibility on using pre-vulcanized natural rubber latex as an admixture for asphalt emulsion in order to improve thermal stability and useful mechanical properties of the asphalt emulsion. The crosslink density was determined by swell ratio. The effect of vulcanizing agent on residue properties of modified asphalt emulsions was studied. The morphology properties of the modified asphalt were also investigated by using an optical microscope. The results showed that asphalt emulsion which was modified using pre-vulcanized NR latex could provide a standard asphalt emulsion and applicable for highway construction application. The mechanical and physical properties of the dried asphalt emulsion were also very well modified by the vulcanized rubber phase. The residue properties of modified asphalt with natural rubber and pre-vulcanized natural rubber latex, including softening point and penetration was improved. The increase in vulcanizing agent could also increase softening point. At low polymer contents, the samples reveal the existence of dispersed polymer particles in a continuous bitumen phase, whereas at high polymer contents a continuous polymer phase was observed.

Abstract: Zinc oxide micropowder was synthesized by a microwave-assisted method. Zinc nitrate and ammonium hydroxide were used as the starting precursors with the mole ratio of 1:1. The white precipitated powder was formed after adding ammonium hydroxide until the pH of final solution was 9 and treated with the microwave radiation power at 1000 Watt for 2-6 min. The phase of zinc oxide micropowder was examined by X-ray diffraction (XRD). A single phase of hexagonal structure was obtained. The morphology and chemical composition of zinc oxide micropowder were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The particle was plate-like in shape with the range of particle size of 0.1-0.5 µm. The elemental composition of zinc oxide showed the characteristic X-ray energy value as follows: zinc of Lα = 1.012 keV, Kα = 8.630 keV and Kβ = 9.570 keV and oxygen of Kα = 0.525 keV, respectively.

Abstract: Generally, a suitable polymer for using as pH indicator packaging should exhibit high porosity to provide a maximum gas permeability which lead to an accurate detection. Ethylene vinyl acetate (EVA) is normally used as such application. However, the gas permeability of EVA was fairly low as 1685.0940 cc/ (m2-day) which not good enough for used as pH indicator packaging application is. To increase a permeability of gas, high porous diatom incorporating with biopolymer was mixed into EVA polymer via internal mixer. It was found that the gas permeability of EVA filled porous diatom/biopolymer was increased up to 4204.2225 cc/ (m2-day). This property is one of the crucial properties for further design for pH indicator packaging in NHAM product.

Abstract: Chulalongkorn University has a long historical background. Pink color is known as the identity color. To be more specific on which pink colors of general prints are acceptable for the identity color of Chulalongkorn University, printed samples with the identity color were collected and measured to find the differences among the printed colors. Then the Natural Color System (NCS) colors were determined corresponding to the printed samples. The obtained NCS colors were used as samples in the experiment. A standard color was obtained from the color of pink cushion placed under Prakeaw, an emblem of Chulalongkorn University. Measurements were taken at the same specific light source as in printed samples. Comparison was then made to determine the color tolerance. A method of pass/fail tolerance was adopted to evaluate the optimum color difference between the identity color and the color of general prints by comparing the results of color measuring device against that of visual assessment. A group of 101 observers were involved to find their perception acceptability of printed pink samples against identity color or standard pink color. The color different equations, E94 and CIEE2000 were employed.

Abstract: The objective of this study is to correlate the crystal structure with material and processing parameters, in particular -nucleating agent and degree of supercooling. The selected -nucleating agent used in this study was “Quinacridone pigment, E3B” with concentration varied from 1 to 100 ppm. The degree of supercooling during sheet extrusion process was controlled by chill roll temperatures in a range of 60 to 115oC. Crystal structures in neat PP and PP-E3B samples were characterized using WAXD and DSC techniques. The selected PP-E3B, with optimum concentration of 5 ppm, was fabricated into sheets using chill roll temperatures of 60, 70, 80, 90, 100, 110 and 115oC; these sheets had -crystal content (K-value) of about 0.099, 0.214, 0.341, 0.430, 0.651, 0.754 and 0.892, respectively. The melting characteristics and physical properties of the nucleated iPP were also dependent upon -crystal content. Finally, it could be concluded that the development of -crystal structure was highly influenced by the concentration of nucleating agent and processing conditions during sheet extrusion.

Abstract: Cobalt ferrite (CoFe2O4) is a soft magnetic material that can be used as fillers in polypropylene. This magnetic polymer composite is studied for its electromagnetic wave absorbing property. To synthesize CoFe2O4 by the polyvinyl alcohol (PVA) sol-gel method, PVA powder was dissolve in distilled water with 5%, 10% and 15% weight per volume. The solution was stirred and regulated at temperature between 60-80°C until turning into PVA gel. Fe and Co powder of atomic ratio 2:1 were then added to the PVA gel with the metal weight per gel volume 1:6, 1:10 and 1: 12. After sintering at 800°C, phases of the synthesized powder were identified by X-ray diffraction (XRD). Magnetic properties of CoFe2O4 were characterized in order to select the appropriate synthesis condition for electromagnetic wave absorbers.