Oligomeric Composition of Polyols From Fatty Acid Methyl Ester: The Effect of Ring‐Opening Reactants of Epoxide Groups

Commercial availability of fatty acid methyl ester (FAME) from palm oil targeted for biodiesel offers a good feedstock for the production of structurally well‐defined polyols for polyurethane applications. The effect of molecular weight (MW), odd and even carbon numbers, and the linear and branched structure reactants used in the ring‐opening reaction of epoxidized fatty acid methyl ester (E‐FAME) on the properties of polyols was investigated. Conversions of E‐FAME to PolyFAME polyols were confirmed by Fourier transform infrared analysis, oxirane oxygen content, and hydroxyl number. Gel permeation chromatography (GPC) calibrated against polyether polyols as a standard and vapor pressure osmometry were used for MW determination. GPC chromatograms of PolyFAME polyols clearly demonstrated the formation of oligomers during ring‐opening reactions. MW, and odd and even carbon numbers in a structure of linear diols and branched diol used in the syntheses of PolyFAME polyols did not have an effect on crystallinity, glass transition, or melt temperatures measured using Differential scanning calorimetry (DSC). PolyFAME polyols ring‐opened with water, methanol, and 1,2‐propanediol contained secondary hydroxyl groups, whereas PolyFAME polyols ring‐opened with linear diols contained a mixture of primary and secondary hydroxyl groups. It was found that the concentration of primary hydroxyl groups increased significantly by increasing the number of carbons from C2 to C3 in the linear diols. The viscosity of PolyFAME polyols also increased with the MW of linear diols used in the E‐FAME ring‐opening reaction. These findings would be beneficial for formulators in choosing the most cost effective polyols for polyurethane formulations.     

Physicochemical stability of calcium alginate beads immobilizing TiO2 nanoparticles for removal of cationic dye under UV irradiation

Recently, there have been considerable interests to immobilize photocatalyst in alginate beads for removing pollutants from water sources. However, the feasibility of using alginate beads in industry largely depends on its long‐term stability during operation. This study investigated the physicochemical stability of alginate/titanium dioxide beads (Alg/TiO₂) when exposed to UV irradiation in aqueous environment. The degradation of Alg/TiO₂ beads was evident because the diameter and mass of the beads was reduced by 12% and 40%, respectively, after 120 h of irradiation. A substantial amount of TiO₂ was leached into the external medium. Consequently, the removal efficiency of model cationic dye was found to reduce after every process cycle. Morphological analysis showed the formation of cavities on the surface of the Alg/TiO₂ beads. Interestingly, the blank alginate beads degraded more rapidly than the Alg/TiO₂ beads, confirming the UV‐shielding effect of TiO₂. Nevertheless, this study reveals the need to improve the UV stability of alginate‐based beads before they can be considered for practical application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45002.     

Characterization of epitaxial GaAs MOS capacitors using atomic layer-deposited TiO2/Al2O3 gate stack: study of Ge auto-doping and p-type Zn doping

Few-wall carbon nanotubes were synthesized by methane/acetylene decomposition over bimetallic Fe-Mo catalyst with MgO (1:8:40) support at the temperature of 900°C. No calcinations and reduction pretreatments were applied to the catalytic powder. The transmission electron microscopy investigation showed that the synthesized carbon nanotubes [CNTs] have high purity and narrow diameter distribution. Raman spectrum showed that the ratio of G to D band line intensities of I _G/I _D is approximately 10, and the peaks in the low frequency range were attributed to the radial breathing mode corresponding to the nanotubes of small diameters. Thermogravimetric analysis data indicated no amorphous carbon phases. Experiments conducted at higher gas pressures showed the increase of CNT yield up to 83%. M?ssbauer spectroscopy, magnetization measurements, X-ray diffraction, high-resolution transmission electron microscopy, and electron diffraction were employed to evaluate the nature of catalyst particles.     

原油脱水站油水分离效果的影响因素和改善措施

针对近年来大庆油田部分原油脱水站存在的问题,研究了影响原油脱水站油水分离效果的主要因素,提出了改进破乳剂的性能和投加机制,降低游离水脱除器进液中机械杂质含量等提高原油脱水站油水分离效果的改善措施。对采出液处理中应用的破乳剂配方及其加药点设置,沉降罐上部污油回收处理工艺进行了改进。在实际应用中显著改善了大庆油田采出液的油水分离效果,电脱水器运行稳定性显著提高,出矿净化原油水含量低于0.3%的控制指标,沉降罐上部油层厚度可控制在0.3m以下,聚驱沉降罐和水驱沉降罐放水含油量可分别降低到500mg/L和300mg/L的控制指标以下。     

Enhanced Dielectric Constant for Efficient Electromagnetic Shielding Based on Carbon-Nanotube-Added Styrene Acrylic Emulsion Based Composite

An efficient electromagnetic shielding composite based on multiwalled carbon nanotubes (MWCNTs)-filled styrene acrylic emulsion-based polymer has been prepared in a water-based system. The MWCNTs were demonstrated to have an effect on the dielectric constants, which effectively enhance electromagnetic shielding efficiency (SE) of the composites. A low conductivity threshold of 0.23 wt% can be obtained. An EMI SE of ~28 dB was achieved for 20 wt% MWCNTs. The AC conductivity (σ _ac) of the composites, deduced from imaginary permittivity, was used to estimate the SE of the composites in X band (8.2–12.4 GHz), showing a good agreement with the measured results.     

Dry Fractionation Approach in Concentrating Tocopherols and Tocotrienols from Palm Fatty Acid Distillate: A Green Pretreatment Process for Vitamin E Extraction

Palm fatty acid distillate (PFAD) is a rich source of vitamin E. As compared to other vegetable oil, PFAD has higher tocotrienol (70–80%) over tocopherol content, which makes it a valuable source for vitamin E extraction. Current vitamin E extraction methods are not sustainable due to the intensive usage of chemical and high operational cost. Hence, the present study investigated for the first time using dry fractionation process as a green and economical pretreatment method for separating solid fraction (stearin) and liquid fraction (olein) in order to concentrate vitamin E from PFAD in olein fraction. We examined the dry fractionation conditions: crystallization ending temperature (36–44 °C), cooling rate (0.3 and 1.5°C min⁻¹), stirring speed (20–125 rpm), and holding time (0–60 min) on the composition of unsaturated and saturated fatty acids as well as vitamin E content in liquid fraction (olein) and solid fraction (stearin) using gas chromatography and high performance liquid chromatography, respectively. In most of these conditions, vitamin E was ultimately higher in olein fraction as compared to stearin fraction, which is correlated with the high degree of unsaturation. Under a cooling rate of 0.3°C min⁻¹, 90 rpm stirring speed, and ending crystallization of 38 °C, the highest vitamin E rich olein fraction was attained with 1479 ± 10.51 ppm in 50 g olein fraction as compared to 1366 ± 7.94 ppm in 500 g of unfractionated PFAD.     

Glass Structure Changes in CO$_{2}$ -Laser Writing of Long-Period Fiber Gratings in Boron-Doped Single-Mode Fibers

We investigate in detail the process of CO₂-laser writing of long-period fiber gratings (LPFGs) in unannealed and annealed boron-doped fiber samples by using repeated scanning of CO₂-laser pulses. We find that the writing dynamics depends strongly on the CO₂-laser energy density and the annealing temperature of the fiber. Our results from analyzing the writing dynamics reveal the relative importance of various physical effects arising from glass structure changes due to different writing conditions and thus provide a better understanding of the formation and the properties of CO₂-laser written LPFGs.     

探讨采用绿色和非绿色模塑料封装的功率MOSFET器件之性能

绿色指令推动半导体厂家在其微电子产品封装中摒弃氧化锑、阻燃剂及卤代化合物之类的环境有害物质,然而人们可能担心,绿色封装中的新化学材料有可能影响半导体器件的性能.本文中通过热压应力测试对采用绿色和非绿色环氧模塑料(EMC)封装的功率晶体管的性能进行了评测.实验表明,绿色器件的电气和物理性能都优于非绿色器件.     

Stable model reference adaptive systems

A method is presented for the design of multivariable model reference adaptive control systems by Lyapunov's second method. The method can be applied to a class of systems in which the misaligned elements of the plant matrices cannot be compensated independently.