2,3-二甲基-4-(2,2,2-三氟乙氧基)吡啶-N-氧化物的合成

以2,3-二甲基吡啶为原料,通过N-氧化、硝化反应制得2,3-二甲基-4-硝基吡啶-N-氧化物,收率69.3%、质量分数98.5%以上;在相转移催化剂的作用下,2,3-二甲基-4-硝基吡啶-N-氧化物与三氟乙醇反应制得2,3-二甲基-4-(2,2,2-三氟乙氧基)吡啶-N-氧化物,收率74%、质量分数98.7%。化合物结构经~1H-NMR、IR确证。结果表明,本方法具有工艺简单、成本低、适应工业化生产的特点。     

Immobilization of β-glucosidase and its aroma-increasing effect on tea beverage

β-Glucosidase was effectively immobilized on alginate by the method of crosslinking–entrapment–crosslinking. After optimization of the immobilized conditions, the activity recovery of immobilized β-glucosidase achieved to 46.0%. The properties of immobilized β-glucosidase were investigated. Its optimum temperature was determined to be 45 °C, decreasing 10 °C compared with that of free enzyme, whereas the optimum pH did not change. The thermal and pH stabilities of immobilized β-glucosidase increased to some degree. The K_m value for immobilized β-glucosidase was estimated to be 1.97 × 10^?3 mol/L. The immobilized β-glucosidase was also applied to treat the tea beverage to investigate its aroma-increasing effect. The results showed that after treated with immobilized β-glucosidase, the total amount of essential oil in green tea, oolong tea and black tea increased by 20.69%, 10.30% and 6.79%, respectively. The storage stability and reusability of the immobilized β-glucosidase were improved significantly, with 73.3% activity retention after stored for 42 days and 93.6% residual activity after repeatedly used for 50 times.     

Different deformation mechanisms of two modified‐polystyrene bimodal systems

It is well known that the dominant toughening mechanism of rubber‐modified polystyrene is multiple crazing. Some researchers have investigated polystyrene that can be modified by rubbers with dual particle sizes, leading to better mechanical properties. That is, the way to absorb energy during the deformation process is crazing and cavitation induced by rubber particles. Two types of polybutadiene‐graft‐polystyrene (PB‐g‐PS) rubber modifiers which have core‐shell structures were synthesized via an emulsion graft polymerization using redox and oil‐soluble initiators, respectively. To balance the yield strength, general‐purpose polystyrene was blended with the PB‐g‐PS modifiers, as well as commercial high‐impact polystyrene. Blends were defined as R‐bimodal and O‐bimodal corresponding to dispersed PB‐g‐PS particles formed using the redox and oil‐soluble initiators, respectively. The impact strength of R‐bimodal was improved significantly by altering the ratio of core to shell. However, little change of impact strength was observed for O‐bimodal. Transmission electron microscopy images of fracture surfaces indicated that the deformation mechanism of R‐bimodal is shear‐yielding induced by multi‐crazing. Moreover, PB‐g‐PS particles dispersed in O‐bimodal can form a ‘cluster’ structure, leading to crazing to absorb energy. Scanning electron microscopy images also showed obvious distinctness between the R‐bimodal and O‐bimodal systems due to different deformation mechanisms. Copyright © 2010 Society of Chemical Industry     

Preparation,characterization and properties of Cr-incorporated DLC films on magnesium alloy

Cr-incorporated diamond-like carbon (Cr-DLC) films were deposited on AZ31 magnesium alloy as protective coatings by a hybrid beams deposition system, which consists of a DC magnetron sputtering of Cr target (99.99%) and a linear ion source (LIS) supplied with CH₄ precursor gas. The Cr concentration (from 2.34 to 31.5 at.%) in the films was controlled by varying the flow ratio of Ar/CH₄. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the microstructure and composition of Cr-DLC films systematically. An electrochemical system and a ball-on-disk tribotester were applied to test the corrosion and tribological properties of the film on the AZ31 substrate, respectively. At low Cr doping (2.34 at.%), the film mainly exhibited the feature of amorphous carbon, while at high doping (31.5 at.%), chromium carbide crystalline phase occurred in the amorphous carbon matrix of the film. In this study, all the prepared Cr-DLC films showed higher adhesion to AZ31 than the DLC film. Especially for the film with low Cr doping (2.34 at.%), it owned the lowest internal stress and the highest adhesion to substrate among all the films. Furthermore, this film could also improve the wear resistance of magnesium alloy effectively. But, none of the films could improve the corrosion resistance of the magnesium alloy in 3.5 wt.% NaCl solution due to the existence of through-thickness defects in the films.     

不完全缩合七苯基三羟基POSS的合成及表征

以苯为溶剂,40%苄基三甲基氢氧化铵的甲醇溶液为催化剂,苯基三氯硅烷水解缩合得到笼状八苯基多面低聚倍半硅氧烷,进一步在四乙基氢氧化铵(35%水溶液)的作用下,以四氢呋喃为溶剂,通过顶点-打开法合成不完全缩合的多面低聚倍半硅氧烷。利用1H、13C、29Si-NMR、FT-IR、元素分析、MALDI-TOF质谱等技术对产物的结构进行了表征,并采用TGA对其热稳定性进行了研究。结果表明,反应主产物为不完全缩合的七苯基三羟基多面低聚倍半硅氧烷,其初始分解温度(失重5%(wt))为516.1℃,热稳定性良好。与以往的合成方法相比,该法显著缩短了反应时间,并提高了产率,从而为POSS在纳米杂化材料领域的应用打下了基础。     

腐植酸类活化剂对磷铵、钙镁磷肥的促释增效研究

应用腐植酸的活化功能,开发磷的高效利用技术,是当前磷肥科技创新中的重要内容。通过室内模拟和玉米盆栽试验,研究了腐植酸类活化剂对磷铵、钙镁磷肥的促释增效作用。结果表明,高效磷铵有较高的抗土壤固定能力,而活化钙镁磷肥的磷释放量明显提高。在等重的情况下,高效磷铵的肥效与普通磷铵的相当,而活化钙镁磷肥的肥效则优于普通钙镁磷肥。     

环保型增塑剂腰果壳油对丁腈橡胶性能的影响

研究了腰果壳油(CNSL)用量对丁腈橡胶胶料的硫化特性和硫化胶性能的影响,并与使用邻苯二甲酸二辛酯和环氧大豆油作为增塑剂进行了对比。结果表明,在0～30份(质量)用量内,加入CNSL后胶料的焦烧时间和正硫化时间有所缩短。与加入相同用量的邻苯二甲酸二辛酯和环氧大豆油的胶料及硫化胶相比,使用CNSL的胶料在硫化曲线上的最小转矩和最大转矩以及硫化胶的硬度、定伸应力和耐ASTM1#标准油体积增加率较小;硫化胶的拉伸强度、撕裂强度、扯断伸长率和耐ASTM3#标准油体积增加率较大;硫化胶的耐热空气老化性能较好。     

29.5R25全钢工程机械子午线轮胎的研究与开发

介绍全钢工程机械子午线轮胎的设计特点和29.5R25无内胎全钢工程机械子午线轮胎的设计。结构设计:外直径1868mm,断面宽732mm,行驶面宽度630mm,胎圈着合直径628mm,花纹深度48mm。施工设计:胎面采用两方三块结构,胎体采用7×7×0.22+0.15HT钢丝帘线,带束层采用3+9+15×0.22+0.15HT钢丝帘线,胎体、带束层和钢丝圈的安全倍数均大于7,成型采用两鼓一次法成型机,硫化采用单模定型硫化机。成品轮胎试验结果表明,充气轮胎外缘尺寸和水压爆破试验结果符合标准要求。     

Polyaniline/carbon black composite as Pt electrocatalyst supports for methanol oxidation: Synthesis and characterization

Core/shell composites of polyaniline (PANI) and Vulcan XC‐72 Carbon (VC), in which the carbon represents the core and PANI forms the shell, were synthesized by in situ chemical oxidation polymerization. Platinum (Pt) particles were then deposited on the PANI/VC composites by chemical reduction method. The highest conductivity is obtained when a mass ratio of PANI/VC equals to 0.28, as proved by Fourier transform infrared spectra. And it is also proved that there are some reactions happened between PANI and VC. Scanning electron microscope, transmission electron microscope, and X‐ray diffraction measurements were performed to analyze their structure and surface morphology. It has been observed that the Pt particles are smaller in size and more uniformly distributed on these composite supports than on pure VC supports, considered as a reference. Methanol oxidation performed on the electrode modified by such a composite catalyst has been measured by cyclic voltammogram focusing on the attenuation of methanol oxidation current after 200 cycles. The attenuation degree for the composite catalyst is only one‐third of the one measured for a simple Pt/VC catalyst. It is proved that the composite catalyst better resist carbon monoxide poisoning in comparison with the Pt/VC catalyst, which may be due to the synergetic effects between the composite support and the Pt catalyst. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermoresponsive surface prepared by atom transfer radical polymerization directly from poly(vinylidene fluoride) for control of cell adhesion and detachment

Thermoresponsive surface was prepared from commercial poly(vinylidene fluoride) (PVDF) films via surface‐initiated atom transfer radical polymerization. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the N‐isopropylacrylamide (NIPAAm) monomer. The PVDF surfaces grafted with poly(N‐isopropylacrylamide) [P(NIPAAm)] were characterized by X‐ray photoelectron spectroscopy. Kinetics study revealed that the P(NIPAAm) chain growth from the PVDF surface was consistent with a “controlled” process. The temperature‐dependent swelling behavior of the surfaces in aqueous solution was studied by atomic force microscope. At 37°C [above the lower critical solution temperature (LCST, about 32°C) of NIPAAm], the seeded cells adhered and spread on the NIPAAm grafted PVDF surface. Below the LCST, the cells detached from the P(NIPAAm)‐grafted PVDF surface spontaneously. The thermoresponsive surfaces are potentially useful as stimuli‐responsive adhesion modifiers in the biomedical fields.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010