Advanced Materials Research Vols. 93-94

Abstract: In this study, a combination of powder printing technique and two-stepped heat treatment was utilized as a mean to prepare porous high density polyethylene structure. Physical and mechanical properties of the resulting structure were then characterized by porosity measurement and monotonic tensile test. It was found that the relationship between structure and properties was strongly influenced by processing conditions including compositions, treatment times and treatment temperatures. This process could increase the properties of porous high density polyethylene significantly over the single-stepped heat treatment without destroying porous structure. Porous high density polyethylene bodies having a porosity ranging from 46-58 percents with tensile strength up to approximately 4 MPa could be successfully prepared in this study.

Abstract: This work studies the effect of PE-g-MA compatibilizer on mechanical thermal and morphological properties of high density polyethylene (HDPE)/titanium dioxide (TiO2) nanocomposites. The HDPE/TiO2 nanocomposites with and without PE-g-MA compatibilizer were prepared by melt mixing technique in a twin screw extruder. The results found that Young's Modulus of HDPE/TiO2 nanocomposites increased with increasing TiO2 contents. The addition of PE-g-MA compatibilizer had no significant effect on the tensile strength and stress at break of HDPE/TiO2 nanocomposites. The decomposition temperatures of HDPE/TiO2 nanocomposites before and after adding PE-g-MA compatibilizer increased with increasing TiO2 contents. The dispersion of TiO2 nanoparticles in HDPE matrix was observed by scanning electron microscope (SEM). The dispersion of nanoparticles in HDPE matrix with PE-g-MA compatibilizer was relatively good, only a few aggregates exited.

Abstract: The aim of this study was focusing on the excipients interaction especially between coloring agents and diluents. There were two coloring agents with different charges ; methylene blue(M) showing positive charge while amaranth(A) giving negative charge but all having same concentration of 0.1% w/w in each mixing batch. There are five types of starch using as diluents; arrowroot starch (W), rice starch (R), cassava starch (S), corn starch (C) and lesser yam starch (l). The physical properties of starch powder and paste (5%w/v) were evaluated as angle of repose and viscosity respectively. While the concentration of both coloring agents were determined by either UV spectroscopy or eye observation. The storage conditions of all samples were kept in both light and dark area for 7 weeks. It was found in powder form that C gave the most stable of M while R gave the worst for m in both light and dark condition. M showed less influences on flow properties of starches than a in a powder state. The flow of C with M gave the best results. The W paste was shown to be the most stable physical properties. M was suitable for S paste in a dark condition. While A was suitable for C, R and W paste in a light condition. The charges of coloring agents might not be a major influence on some physical properties of starch in both powder and paste form.

Abstract: Bismuth vanadate powder was synthesized by the hydrothermal method with bismuth nitrate and ammonium vanadate as the starting precursors with the mole ratio of bismuth and vanadium of 1:1. The mixed solution was adjusted with ammonium hydroxide until the pH of final solution was 7 and hydrothermally treated at 100 °C for 2-6h. The phase was studied by X-ray diffraction (XRD). Monoclinic structure was obtained after hydrothermal treated at 100 °C for 6h without calcination step. The morphology was investigated by scanning electron microscopy (SEM). The particle was needle-like in shape and highly agglomerate. The degradation of methylene blue over photocatalyst bismuth vanadate powder was examined by ultraviolet spectroscopy (UV). Bismuth vanadate powder synthesized by the hydrothermal method at 100 °C for 6h showed the highest photocatalytic activity.

Abstract: Stainless steel/carbon nanotubes (CNTs) nanocomposite powders were synthesized by chemical vapor deposition (CVD) method with ethanol as a carbon source. The effects of synthesis temperature and time on microstructure and chemical composition of the powders were investigated. The as-received stainless steel powders were synthesized at temperature in between 550-800°C for 30-180 min at a pressure of 10 Torr. The optimum synthesis condition was found to be 800°C for 120 min. Average diameter of CNTs grown on stainless steel particles slightly increased with increasing growth temperature. The synthesis time, however, was found to have no effect on the size of CNTs.

Abstract: Modification of poly(vinyl alcohol) (PVA) by esterification is one of alternative ways to prepare copolymers. The degree of esterification on PVA was determined by FTIR, 1H-NMR, and elemental analysis. Both polymers, i.e., PVA and esterified PVA were mixed with carbon black in DMSO and prepared as thin films onto the interdigited electrodes (IDE) by spin-coating technique to obtain chemical sensors. To investigate the chemical vapour sensing property, the chemical sensors were examined with various organic solvents such as hexane, toluene, alcohols, THF, ethyl acetate, etc.

Abstract: This work presents a micromechanics-based model to investigate the effective thermo-electric properties of piezoelectric composite materials. The effective thermo-electric properties are derived by considering a multi-coated ellipsoidal inhomogeneity embedded in a host material in the framework of the generalized self-consistent method (GSCM). An incremental scheme, in which the reinforcements are incrementally put in the host material, is implemented. The validation of the micromechanical model is performed with experimental data. The model proposed has a wide range of applications and can be extended to other physical properties.

Abstract: We have fabricated dye-sensitized solar cells (DSSCs) with quasi-solid state electrolytes base on N-methyl-quinoline iodide and studied the performance and stability of the cells at different temperatures. The quasi-solid state electrolytes were prepared from polymer gel electrolyte based on N-methyl-quinoline iodide and iodine. Pure-anatase nanocrystalline TiO2 films with absorption of standard N719 dye were employed as working electrodes. The maximum efficiency of the solar cells was 4.5 % under incident light of 100 mW/cm2. The cells also showed excellent stability for several months under irradiation of sunlight. The ionic conductivity of the electrolytes and the performance of the cells at different temperatures were presented.

Abstract: Poly(lactic acid-co-ethylene glycol) (PLLA/PEG) copolymers were synthesized and their properties were characterized. The PLLA/PEG/PLLA triblock copolymers were synthesized by ring-opening polymerization from l-lactide (LLA) and PEG macroinitiator. Stannous octoate, Sn(Oct)2 was used as a catalyst. Effects of molecular weight of PEG (600, 2000 and 4000), LLA/OH molar ratios (95:5, 98:2) and a sequence of addition of the reactants on properties of the copolymers were investigated. The triblock copolymers were subsequently used in a production of multiblock copolymers by reacting with a chain-extending agent, hexamethylene diisocyanate (HMDI). Chemical structure and molecular weight of the copolymers were characterized by 1H-NMR, FTIR and GPC. The results showed that molecular weight of triblock copolymers varied from 4,500 to 10,200. After chain extension, multiblock copolymer with molecular weight of 16,490 was produced. Thermal properties of the copolymers were also examined by DSC.

Abstract: Astaxanthin is a natural carotenoid pigment with powerful antioxidant capacity which has been reported for beneficial effects on human health to prevent cancers and anti-degenerative diseases. Bioavailability of astaxanthin is however limited due to insoluble and instable properties of its lipophilic nature. This study describes the cytotoxicity and astaxanthin delivery using a surfactant (tween 80) and penetration enhancers (methyl -cyclodextrin and liposome) to enhance astaxanthin bioavailability in human hepatocellular carcinoma cell line. Toxicity of tween 80 and methyl -cyclodextrin increased with concentration. Liposome did not alter cell viability relative to untreated controls, regardless of concentration tested. Cellular uptake among delivery vehicles was compared at 24 hours and was found to be higher than that of astaxanthin without a vehicle. The cellular uptake rate was highest when liposome was used as the delivery vehicle. This finding aids in the development of design criteria for vehicles for delivery of antioxidants to cells.