聚硅氧烷嵌段聚氨酯／环氧树脂IPN的动态力学性能与形态结构

以甲苯-2,4-二异氰酸酯(TDI)、聚醚二元醇为主要原料制得-NCO封端的聚氨酯预聚体,其中加入少量端氨基聚硅氧烷,利用-NH2与-NCO反应而将聚硅氧烷链嵌段引入到聚氨酯预聚物链中,然后按一定比例加入环氧树脂E-51,并加入扩链剂、交联剂等,充分混匀后固化得到聚硅氧烷嵌段聚氨酯/环氧互穿网络聚合物(IPN)。对材料进行了扫描电镜(SEM)测试和动态力学分析(DMTA),结果表明,该互穿网络聚合物在-100℃~110℃范围内阻尼损耗因子tanδ>0.3,是一种优良的宽温域高性能阻尼材料,其性能与聚硅氧烷的含量和分子量的大小密切相关。     

有机硅-聚氨酯-环氧树脂三元共聚物的合成及表面性能研究

以甲苯-2,4-二异氰酸酯(TDI)、聚醚二元醇为主要原料制得-NCO封端的预聚体,并按一定比例和环氧树脂E-51混合均匀;另用3-氨丙基三乙氧基硅烷(硅烷偶联剂550)、八甲基环四硅氧烷(D4)合成一系列分子量不同的氨丙基聚硅氧烷,利用多元胺作固化剂,合成一系列氨丙基聚硅氧烷改性聚氨酯/环氧共聚物。测试了材料的力学性能、表面接触角、吸水率,同时对材料进行了表面电子能谱(ESCA)分析。结果表明:氨丙基聚硅氧烷-聚氨酯-环氧三元共聚物具有良好的拉伸强度、疏水性能以及较低的表面张力。     

线型聚硅氧烷改性聚醚型聚氨酯/环氧树脂互穿聚合物网络

以端羟基聚硅氧烷(PDMS)、4,4,-二苯甲烷二异氰酸酯(MDI)、聚醚多元醇为原料制得端异氰酸酯基(-NCO)聚氨酯预聚体,再与环氧树脂E-44反应制得一系列聚硅氧烷改性聚氨酯/环氧树脂互穿聚合物网络。通过红外光谱、接触角、拉伸试验、动态力学分析、扫描电子显微镜对聚合物体系的结构与性能进行了研究和表征。实验结果表明,聚硅氧烷的引入使得互穿聚合物网络的表面疏水性增强,表面自由能降低,拉伸强度下降但断裂伸长率升高。随着聚硅氧烷用量的增加,聚合物体系的玻璃化转变温度从-45℃提高到了-36℃。     

接枝和非接枝聚氨酯/环氧树脂互穿网络聚合物的制备及其性能

采用分步法分别制备了接枝和非接枝聚氨酯(PU)/环氧树脂(EP)互穿网络聚合物(IPNs),研究了不同配比对材料力学性能和热性能的影响。红外结果显示接枝聚氨酯/环氧树脂互穿网络聚合物分子间形成了氨基甲酸酯的接枝结构;力学性能测试结果表明,聚氨酯的引入显著地提高了材料的力学性能,当m(PU)∶m(EP)=15∶85时,接枝聚氨酯/环氧树脂互穿网络聚合物的拉伸和冲击强度达到最大值(分别为36.7MPa和22.39kJ/m2),当m(PU)∶m(EP)=10∶90时,非接枝互穿网络聚合物拉伸和冲击强度达到最大值(分别为27.8MPa和19.34kJ/m2);TGA结果证实接枝互穿网络聚合物的热稳定性明显优于非接枝互穿网络聚合物。     

聚醚型聚氨酯/环氧树脂互穿网络聚合物的结构与性能研究

以4,4’-二苯基甲烷二异氰酸酯和聚醚及双酚A型环氧树脂为原料经共聚合成了聚氨酯(PU)/环氧树脂(EP)互穿聚合物网络(IPNs).通过改变聚氨酯结构及环氧树脂含量制备系列PU/EP的IPNs,并对其性能进行了研究.研究表明随着聚氨酯中两官能度聚醚用量增加,IPNs体系的亲水性增强、表面自由能增大;此外随着环氧树脂含量增多,整个IPNs体系的疏水性增强;力学性能测试表明,聚氨酯结构以及环氧树脂含量对PU/EP的IPNs材料力学性能影响较大.     

聚醚氨酯/环氧丙烯酸酯树脂同时互穿网络的研究

通过改变聚醚氨酯和环氧丙烯酸酯树脂组分比，合成了不同组成的同时互穿网络聚合物（SINs），采用红外光谱，扫描电镜和动态热力学分析等测试方法，研究了SINs材料的组分间分子混合和形态结构，探讨了材料的组分与力学及热学性能的关系。结果表明，互穿聚合物网络间存在微观相分离，两个聚合物网络间形成了部分的“网标交联”结构，SINs材料的力学和热学性能均有提高，当材料中聚醚氨酯和环氧丙烯酸酯树脂组分比为30／70（质量比）时，是综合力学性能和热学性能最好的塑料。     

MDI聚氨酯/聚硅氧烷IPN的结构与力学性能

用MDI聚醚氨酯和含少量苯基的聚二甲基硅氧烷合成了一系列的聚氨酯／聚硅氧烷IPN阻尼弹性体，研究了材料的结构与力学性能．结果表明，当聚氨酯与聚硅氧烷的质量比为90：10时。IPN的抗张强度达41．57MPa，断裂伸长率为376％，并具有良好的阻尼性能，玻璃化转变温度范围大于80℃．聚氨酯／聚硅氧烷IPN具有细微的微相分离结构，聚硅氧烷在IPN中的微相尺寸为微米级，并趋向于分布在IPN的表面．     

可扩链双马来酰亚胺对聚氨酯-环氧树脂基体的改性及性能表征

采用可扩链的双马来酰亚胺(BMI)和聚氨酯改性环氧树脂在4，4’-二氨基二苯基甲烷存在下固化制备了MBI改性聚氨酯-环氧树脂内部交联网络聚合物，通过红外光谱分析证实了聚氨酯在环氧骨架上的接枝，并对改性材料的力学性能、热性能和形态学进行了研究。由力学性能及热性能的研究结果表明聚氨酯与环氧树脂的复合提高了环氧树脂的机械强度，但同时也降低了玻璃化转变温度和热稳定性，而BMI与聚氨酯-环氧树脂体系的复合提高了材料的热稳定性、拉伸强度和弯曲强度，降低了材料的冲击强度和玻璃化转变温度。我们还利用扫描电子显微镜分别研究了聚氨酯改性环氧树脂和可扩链的BMI改性聚氨酯-环氧树脂体系的表面形态。     

植物油互穿聚合物网络的研究

将植物油（蓖麻油、棉籽油）进行环氧化反应得到环氧植物油；将桐油与顺丁烯二酸酐作用得到桐油酸酐；植物油或环氧树脂及其固化剂（桐油酸酐）与聚氨酯预聚物（ＰＵＰ）及其扩链剂等混合固化，合成了一系列植物油聚合物／聚氨酯互穿聚合物网络（ＩＰＮ）。经动态力学测试结果表明，该类聚合物共混物体系组分间的相容性好，在动态力学谱上一般只有１个较宽的峰，ｔｇδ值持续大于０．３的温域宽度在９０℃左右，有的超过１００℃，大大加宽了相应植物油交联共聚物或聚氨酯的阻尼温域。这类互穿聚合物网络是一类以植物油为主要原料、制备成本低、方法新、阻尼性能优良的新型阻尼材料。文中还对组成与性能的关系进行了讨论     

聚氨酯与环氧树脂乳液互穿网络聚合物的制备

聚氨酯是一种无溶剂型的环保材料，传统聚氨酯以聚酯类与聚醚类多元醇为主[1]，而这两种软段合成的聚氨酯的耐水性能与力学性能等有待提高[2][3]。聚碳酸亚丙酯二醇拥有较好的力学性能与耐水解能力。本研究采用聚碳酸亚丙酯二醇(PCD-2000)为软段[4]合成聚氨酯(WPU)。在此基础上，使用互穿网络技术，制备聚氨酯与聚丙烯酸酯的乳液互穿网络聚合物[5](PU/EP LIPN)。本实验主要探究了聚氨酯与环氧树脂的乳液能否形成互穿网络聚合物；不同环氧树脂固化剂添加方式对PU/EP LIPN的影响；不同量的后扩链[6]和固化剂加入量对PU/EP LIPN的涂膜性能的影响。实验结果表明，聚氨酯中的环氧树脂已经固化，成功建立了互穿网络结构；使用环氧树脂聚合物对聚氨酯进行改性之后，断裂伸长率明显下降，耐水性提高；在0.5后扩链系数时，乳液胶膜拥有较好的成膜性能，力学强度；耐水性随后扩链系数的变大先增强后减弱。     

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.……     

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.……     

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 ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.