Crystallization Behavior of Diacylglycerol-Rich Oils Produced from Rapeseed Oil

We examined the crystallization behavior of high-melting fractions in liquid oil containing high concentrations of diacylglycerols (DAG >80%) (hereafter referred to as DAG-rich oil). By differential scanning calorimetry and optical microscopy at moderate cooling rates, crystallization in the DAG-rich oil was detected at around 6 °C. It was found that the crystallization extent increased with decreasing temperatures of crystallization below 0 °C. A gas chromatographic analysis was performed on the crystallized fractions, which were separated by filtration at different periods of isothermal crystallization at 3 °C. The results indicated that at earlier crystallization periods, the concentrations of 1,3-disaturated DAG such as palmitic and stearic acid moieties (15 min) and 1,3-saturated–unsaturated mixed-acid DAG including oleic acid, palmitic, and stearic acid moieties (15 min–3 h) were predominant. However, the concentrations of 1,3-diunsaturated DAG including oleic acid moiety increased after a crystallization period of 6 h. To clarify the sequential crystallization process of DAG, we examined the binary mixing behavior of principal DAG components occurring in the rapeseed-based DAG-rich oil. It was evident that 1,3-disaturated DAG, 1,3-saturated–unsaturated mixed-acid DAG, and 1,3-diunsaturated DAG exhibited immiscible behavior. From these data, basic information on the precipitation processes in DAG-rich oils at chilled temperatures was obtained.     

厚板镦粗－翻边复合工艺

传统圆孔翻边工艺中,翻边高度和形状精度是制约板料成形极限的主要因素。为了获得较为稳固的翻边凸起部位,提出采用镦粗一翻边复合工艺成形厚板翻边凸起结构。利用DEFORM有限元软件对镦粗一翻边复合工艺过程进行数值模拟,分析各工艺参数对翻边高度的影响规律;对A1050P-O厚板进行了镦粗一翻边工艺试验并讨论了翻边后的板料硬度分布规律。结果表明：与传统翻边工艺相比,镦粗一翻边工艺的翻边凸起部位精度更好、翻边高度更高,且有限元模拟结果与试验结果保持了较好的一致性。成形后的板料由于加工硬化影响,翻边凸起结构的硬度增大,有利于零件的后续加工组装工序。     

Dielectric breakdown properties of polylactic acid with β‐crystalline chitin

β‐Crystalline chitin was added to polylactic acid (PLA), and this PLA was then heat treated at 100 °C for 1 min. The crystallinity of the heat‐treated PLA increased to more than 40%, and its crystallization speed also increased significantly. Furthermore, the temperature dependence of the dielectric breakdown strength (E_B) was checked, and it was found that at a temperature of 80 °C, the E_B value of the PLA with chitin was around 1.8 times greater than that of the PLA without chitin. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Stability and Oil Migration of Oil‐in‐Water Emulsions Emulsified by Phase‐Separating Biopolymer Mixtures

Oil‐in‐water (O/W) emulsions with varying concentration of oil phase, medium‐chain triglyceride (MCT), were prepared using phase‐separating gum arabic (GA)/sugar beet pectin (SBP) mixture as an emulsifier. Stability of the emulsions including emulsion phase separation, droplet size change, and oil migration were investigated by means of visual observation, droplet size analysis, oil partition analysis, backscattering of light, and interfacial tension measurement. It was found that in the emulsions prepared with 4.0% GA/1.0% SBP, when the concentration of MCT was greater than 2.0%, emulsion phase separation was not observed and the emulsions were stable with droplet size unchanged during storage. This result proves the emulsification ability of phase‐separating biopolymer mixtures and their potential usage as emulsifiers to prepare O/W emulsion. However, when the concentration of MCT was equal or less than 2.0%, emulsion phase separation occurred after preparation resulting in an upper SBP‐rich phase and a lower GA‐rich phase. The droplet size increased in the upper phase whereas decreased slightly in the lower phase with time, compared to the freshly prepared emulsions. During storage, the oil droplets exhibited a complex migration process: first moving to the SBP‐rich phase, then to the GA‐rich phase and finally gathering at the interface between the two phases. The mechanisms of the emulsion stability and oil migration in the phase‐separated emulsions were discussed.     

Wettability of pure Ti by molten pure Mg droplets

The wetting behavior of molten pure Mg droplets on pure Ti substrate, a crucial phenomenon in the design of Mg matrix composites reinforced with Ti particles, was investigated by the sessile drop method. The contact angle was measured in high-purity argon (99.999%) at 1073 K. In particular, the effects of two important parameters on the contact angle were evaluated: Mg evaporation during the wetting test; and surface oxide film of the substrate. The calculation method to estimate the modified contact angle involved taking the morphological changes of the droplet outline due to the evaporation into consideration. By changing the thickness of the surface oxide films on the Ti substrate, it was possible to examine the wettability and the chemical reactions at the interface between the solidified Mg drop and the substrate were investigated by scanning electron microscopy–energy dispersive X-ray spectrometry analysis. At the initial wetting stage, a large contact angle with 95–110° was obtained, which depended on the reduction of TiO₂ surface films by Mg droplets. When the molten Mg contacts an area of pure Ti after reduction, the contact angle suddenly decreased. The equilibrium value at the stable state strongly depended on the surface roughness of the Ti plate.     

Selective hydrogenation of cinnamaldehyde over Raney cobalt catalysts modified with salts of heteropolyacids

The hydrogenation of cinnamaldehyde to cinnamyl alcohol was carried out over Raney cobalt catalysts modified by Cu_3/2PMo₁₂O₄₀. It was found that the conversion of cinnamaldehyde decreases substantially with increases in the amount of Cu_3/2PMo₁₂O₄₀ deposited on Raney cobalt catalysts. The maximum yield of cinnamyl alcohol varies with the amount of deposited Cu_3/2PMo₁₂O₄₀. The more the deposited modifier, the higher the attainable maximum yield of cinnamyl alcohol. With 2.8% Cu_3/2PMo₁₂O₄₀ modified Raney cobalt, the selectivity for cinnamyl alcohol does not change with reaction temperature and reaction time. Thus, it is likely that the selectivity of ca. 80% for cinnamyl alcohol represents a specific value which is related to the nature of the surface modifier, Cu_3/2PMo₁₂O₄₀. The influences of the heteropolyanions and the competitive cations on the conversion and the selectivity were also investigated. It was found that copper salts of different heteropolyacids acting as the modifier of the catalyst bring about different enhancements in the selectivity for cinnamyl alcohol. The order of enhancement of selectivity in terms of heteropolyacid anion is PMo₁₂O³⁻₄₀>SiMo₁₂O⁴⁻₄₀>PW₁₂O³⁻₄₀. There is little difference in selectivity by modification with (NH₄)₆Mo₇O₂₄ and Cu₂SiMo₁₂O₄₀. Raney cobalt catalyst modified by different 12-molybdophosphate containing cations of alkali, alkaline earth and transition metals gives a similar selectivity of about 75%. Among all of the 12-molybdophosphates, that containing the cation Cu²⁺ is the best in improving the selectivity of the catalysts. A selectivity as high as 83% was attained when an amount of 2.8% Cu_3/2PMo₁₂O₄₀ was deposited on the catalyst.     

以稻壳为强化原料制备低成本钛合金的摩擦学性能

以稻壳热解产物为SiO₂源,通过粉末冶金法制备了Si和O固溶强化的低成本钛合金,并从磨损率、磨损表面形貌和磨屑成分等角度系统研究了其摩擦学性能和磨损机理。结果表明,随着SiO₂加入量的增加,Ti合金的体积磨损率显著降低,与硬度的变化规律吻合良好,同时磨损表面有三处变化,即犁沟的深度变浅、塑性变形程度降低和磨屑的尺寸变小和数量减少。SiO₂的加入使磨损机制从纯Ti的粘着和磨料磨损转变为磨料和氧化磨损,而磨屑尺寸的减小可归因于GCr15球和钛基体反复摩擦,导致磨屑的脆化。本文提供了一种使用农业废稻壳生产具有优良综合性能的钛合金方法,在降低钛合金成本的同时也有益于生态环境的保护。     

Influence of gelling conditions on mechanical properties of simultaneous interpenetrating polymer networks from epoxy and bismaleimide resins

Simultaneous interpenetrating polymer networks (SINs) were prepared from nadic methyl anhydride-cured epoxy resin and bismaleimide (BMI) of which the composition ratios were, respectively, comprised of 3/1 (EM-25 series) and 1/1 (EM-50 series), under different gelling conditions for both resins. Dynamic mechanical and tensile properties were measured for these SINs. Turbidity was also measured to obtain some information regarding morphology. Although the rubbery modulus was constant irrespective of a gel-time ratio (Gt) of the epoxide resin to that of BMI for the EM-25 series, it increased with increasing Gt for the EM-50 series. The glass transition temperature (T_g) was nearly constant at Gt < 1 and then decreased with increasing Gt at Gt > 1 for the EM-25 series. On the other hand, T_g was nearly constant irrespective of Gt for the EM-50 series, though the values of T_g at Gt < 1 were somewhat higher than those at Gt > 1. There was an appropriate value of Gt that gave better tensile strength (σ_b) or toughness evaluated by the area under a stress-strain curve. The T_g and σ_b were found to be correlated to the turbidity of the SINs. The above mechanical behavior can be explained in terms of the molecular mixing and morphology that vary with a change in the relative polymerization rate of both the resins. © 1993 John Wiley & Sons, Inc.     

New Magnesium Composite with Mg17Al12 Intermetallic Particles

Powder Metallurgy and Metal Ceramics - Although magnesium is one of the materials with the lowest density, its application is limited amongst other commercial materials due to insufficient...