聚四甲基对硅亚苯基-二苯基硅氧烷共聚物的制备及其耐热性能

以1,4-双(二甲基硅基)苯(BDSB)和二苯基二甲氧基硅烷为原料,B(C6 F5)3为催化剂,通过Si-H/Si-OR缩聚的方法制备了聚四甲基对硅亚苯基-二苯基硅氧烷共聚物(PTMPS-DPS).研究了催化剂用量、反应温度对缩聚反应的影响,并用29Si NMR对产物的微观结构进行表征,用TG、DSC对产物的热性质进行了表征.制备PTMPS-DPS适宜的反应条件是:B(C6 F5)3浓度6.3mml/kg,反应温度60℃.微量水分能增加产物的嵌段性.产物接近于交替结构,嵌段数为96,T8=-5.2℃,在N2、空气中的5%热失重温度分别是357℃、360℃,700℃时的残留分别为32%、37%.     

嵌段共聚有机硅氧烷的合成及其氧化热稳定性研究

采用对－双（二甲基－锂氧硅基）苯撑作引发剂，Ｎ，Ｎ－二甲基甲酰胺作促进剂，不同的有机环四硅氧烷作单体，制备了数种不同组成的聚二苯基硅氧烷（Ｐ）－聚二甲基－甲基乙烯基硅氧烷（ＭＶ）－聚二苯基硅氧烷（Ｐ）三嵌段（Ｐ－ＭＶ－Ｐ）共聚物。这些嵌段共聚物，经石油醚溶解，乙醇萃取低分子量物质，得到了具有良好的氧化热稳定性的有机硅材料。     

二甲基 - 二苯基聚硅氧烷与二甲基 - 甲基乙烯基聚硅氧烷嵌段共聚研究

利用聚二甲基－二苯基硅氧烷二醇（Ａ）与聚二甲基－甲基乙烯基硅氧烷二醇（Ｂ），在辛酸己胺催化下缩合聚合、形成（ＡＢ）ｎ、（ＡＢ）ｎＡ及（ＢＡ）ｎＢ型嵌段共聚物。该类聚合物经１ＨＮＭＲ、ＵＶ、ＩＲ及特性粘数测定，研究了催化剂用量、反应时间及反应温度对分子量的影响。利用分步沉淀分级得出了分子量分布。     

嵌段共聚有机硅氧的合成及其氧化热稳定性研究

采用对－双（二甲基－锂氧硅基）苯撑作引发剂，Ｎ，Ｎ－二甲基甲酰胺促进剂，不同的有机环四硅氧烷作单体，制备了数种不同组成的聚二苯基硅氧烷－聚二甲基－甲基乙烯基硅氧烷二苯基硅氧烷三嵌段共聚物。这些嵌段共聚物，经石油醚溶解，乙醇萃取低分子量是到了具有良好的氧化热稳定性的有机硅材料。     

含硅酰胺-胺固化环氧树脂的研究

主要描述了用二甲基乙酰胺作为溶剂，以4，4’-二氨基二苯基醚，4，4’-二氨基二苯基甲烷。4。4，-二氨基二苯基砜，3，3’-二氨基二苯基砜，二（3-氨基苯基）甲基氧化膦。三（3-氨基苯基）氧化膦分别与二（4-酰氯苯基）二甲基硅烷反应制备含硅的酰胺-胺固化剂的方法，并采用傅里叶变换红外光谱（FTIR）和^1H核磁共振（^1HNMR）对酰胺-胺的结构进行了表征。以制得到的芳香族酰胺-胺为固化剂，研究了其结构和分子大小对双酚A二缩水甘油醚（DGEBA）固化和热性能的影响。在以化学计量的含硅芳香酰胺-胺固化时。采用示差扫描量热法（DSC）对DGEBA的固化行为进行了研究。结果显示所有样品在200-300℃温度范围内存在宽的放热转变过程，而且在使用含磷酰胺固化时。放热峰温度值最小，在使用含醚酰胺固化时。放热峰温度值最大。在氮气气氛下，采用动态热重分析法对等温固化树脂的热稳定性进行了研究，结果显示含硅酰胺的存在大大提高了焦炭残余率，并且在硅和磷共同作为阻燃元素时存在最大值。     

二甲基—二苯基聚硅氧烷与二甲基—甲基乙烯基聚硅氧？…

利用聚二甲基－二苯基硅氧烷二醇（Ａ）与聚二甲基－甲基乙烯基硅氧烷二醇（Ｂ），在辛酸己胺催化下缩合聚合、形成（ＡＢ）ｎ、（ＡＢ）ｎＡ及（ＢＡ）ｎＢ型嵌段共聚物。该类聚合物经＾１ＨＮＭＲ、ＵＶ、ＩＲ及特性粘数测定，研究了催化剂用量、反应时间及反应温度对分子量的影响。利用分步沉淀分级得出了分子量分布。     

4，4＇-二氨基甲酸酯-二苯基丙烷的热分解反应

用傅立叶红外光谱（FT—IR）法和示差扫描量热（DSC）法研究了4，4’-二氨基甲酸酯-二苯基丙烷（DCB）的热分解反应。结果表明，DCB在180℃以下即可以发生热分解反应，此时的反应主要是DCB分解成胺和CO2；在180℃以上，DCB还将分解成酚和异氰酸，酚进一步与DCB反应生成碳酸二酯和氨；DCB的热分解在200℃以上呈现加速的趋势。水的存在，促进了DCB分解成胺和CO2的反应。     

笼型β-氨乙基-γ-氨丙基倍半硅氧烷／环氧树脂的固化过程与动力学

为提高环氧树脂的热性能,用动态DSC对笼型β-氨乙基-γ-氨丙基倍半硅氧烷(POAAS)/E-51环氧树脂体系的固化过程进行研究,表明N=0.5为最佳配比,固化反应放热峰值温度Tp为82 ℃,反应终了温度Tf为135 ℃.依据Kissinger方程求得固化反应的活化能为50.26 kJ/mol,依据Crane方程得固化反应级数为1.126,固化反应动力学的数学模型为da/dt=4.08×106 exp(-50255/8.314T) (1-a)1.126.     

笼型β-氨乙基-γ-氨丙基倍半硅氧烷/环氧树脂的固化过程与动力学EI北大核心

为提高环氧树脂的热性能,用动态DSC对笼型β-氨乙基-γ-氨丙基倍半硅氧烷(POAAS)/E-51环氧树脂体系的固化过程进行研究,表明N=0.5为最佳配比,固化反应放热峰值温度Tp为82℃,反应终了温度Tf为135℃。依据Kissinger方程求得固化反应的活化能为50.26 kJ/mol,依据Crane方程得固化反应级数为1.126,固化反应动力学的数学模型为da/dt=4.08×106exp(-50255/8.314T)(1-a)1.126。     

聚二羟基甲基硅氧烷改性聚醚酯弹性体的合成与表征

以对苯二甲酸二甲酯(DMT)、1,4丁二醇(BD)、聚乙二醇(PEG)和聚二羟基甲基硅氧烷(PDMS)为原料,采用熔融缩聚法一步合成了聚硅醚酯弹性体(PBT-co-PEG/PDMS)。通过红外光谱、核磁共振和凝胶色谱等分析方法对其分子结构和分子量进行了表征,用差示扫描量热(DSC)和热重分析(TG)研究了耐热性能,结果发现,PEG和PDMS参与了共聚反应,随着聚合物中聚二羟基甲基硅氧烷含量的增加,聚合物的数均分子量相应减小,PDMS含量为10%的共聚物数均分子量仅为3万;热分析结果表明,随着PDMS含量的增加,聚合物的熔点从175℃逐渐升高到200℃,同时起始降解温度也逐步提高。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...