端羟基聚丙烯酸丁酯的合成与表征

以α-溴代异丁酸乙酯为引发剂,采用原子转移自由基聚合(ATRP)合成了分子量为500的聚丙烯酸丁酯。以N-甲基单乙醇胺作为亲核试剂,对带有活性溴端基的聚丙烯酸丁酯进行亲核取代反应,得到了一端带有羟基的聚丙烯酸丁酯。利用红外光谱仪、核磁共振谱仪、凝胶渗透色谱仪等对产物的结构进行表征。结果表明,成功合成了端羟基聚丙烯酸丁酯,且聚合物分子量可控,分子量分布窄(PDI=1.09)。     

原子转移自由基聚合制备ABA型嵌段共聚物

以α，α’－二溴代二甲苯为引发剂，CuBr/2,2‘－联吡啶为催化体系，制备了双溴端基的分子量分布窄的聚苯乙烯（MWD＝1．21）。再以此作为大分子引发剂，实现了甲基丙烯酸甲酯的原子转移自由基聚合，制得了分子量可控且分子量分布窄的ABA型嵌段共聚物，即聚甲基丙烯酸甲酯－b－聚苯乙烯－b－聚甲基丙烯酸甲酯。     

21臂星形两亲性嵌段共聚物β-CD-g-21（PS-b-PAA）的合成与表征

通过连续原子转移自由基聚合(ATRP)技术,首次合成出3个系列以β-环糊精(β-CD)为核心、内嵌段为刚性链聚苯乙烯(PS)、外嵌段为聚丙烯酸(PAA)的21臂两亲性星形嵌段共聚物β-CD-g-21(PS-b-PAA)。并利用核磁氢谱、红外光谱、凝胶色谱对所得聚合物的化学结构、相对分子质量及其分布进行了表征。证实β-CD的21个羟基均发生了聚合反应,所得的共聚物相对分子质量分布窄,均在1.35以下。通过水解嵌段聚合物大分子链和β-CD之间的酯键,计算出PSb-PAA的相对分子质量分别为3100、4200、5800。实验结果表明,合成出的星形嵌段聚合物结构明确,相对分子质量分布可控。     

PMMA-b-PHEA嵌段共聚物的制备和表征

采用分步法合成了两嵌段共聚物聚甲基丙烯酸甲酯-b-聚丙烯酸-2-羟乙酯(PMMA-b-PHEA):首先采用AIBN作为引发剂,FeCl3/PPh3作为催化体系,通过MMA的反向原子转移自由基聚合(RA-TRP),得到含端基Cl的M-n为17128聚合物PMMA-Cl;然后以PMMA-Cl为大分子引发剂,FeCl2/PPh3为催化体系,引发丙烯酸-2-羟乙酯(HEA)的原子转移自由基聚合(ATRP),得到的产物PMMA-b-PHEA分子量分布达到1.32,凝胶渗透色谱(GPC)、红外光谱(FTIR)、核磁共振(1HNMR)、差示扫描量热仪(DSC)和热重分析仪(TGA)对产物结构进行了表征,证实了嵌段共聚物PMMA-b-PHEA的生成。     

二乙烯苯为支化单体的支化聚苯乙烯合成反应

以α-溴代异丁酸叔丁酯(t-BBiB)为引发剂,二乙烯苯(DVB)为支化单体,在90℃的条件下经原子转移自由基聚合(ATRP)合成支化聚苯乙烯。用气相色谱(GC)、核磁共振(1H-NMR)和三检测体积排除色谱(TD-SEC)对聚合反应过程和聚合物进行了分析表征。结果表明,在聚合体系中少量带有贫电子双键的共聚单体甲基丙烯酸丁酯(BMA)存在下,能提高引发剂效率,可以在高单体转化率下(>95%)保证聚合反应体系不交联,合成得到高分子量的支化聚苯乙烯,而且分子量分布相对较窄。     

葡萄糖还原FeBr_3催化下的甲基丙烯酸甲酯原子转移自由基聚合

以葡萄糖为还原剂,FeBr3为氧化剂,通过氧化还原反应,在反应体系中原位生成FeBr2催化剂,以2,2’-联吡啶(bpy)为配位剂,1-溴乙基苯为引发剂,在110℃进行甲基丙烯酸甲酯原子转移自由基聚合。结果表明,聚合反应符合对单体浓度为一级的动力学关系,聚合物分子量随单体转化率呈线性增加,分子量分布较窄,M-w/-Mn在1.17～1.25之间,具有明显的活性聚合特征,并且在有氧的环境下同样能够进行活性聚合,该聚合方法明显优于常规的原子转移自由基聚合和反向原子转移自由基聚合。     

可控活性自由基聚合的研究进展

可控活性自由基聚合(CRP)是一种合成具有设计微观结构和窄分子量分布聚合物的方法,原子转移自由基聚合(ATRP)较其它CRP方法具有分子设计能力较强等优点,是应用最广泛的CRP。文中简要介绍了CRP的分类,同时以ATRP为例从单体、引发剂、催化体系等方面讨论了CRP聚合体系的发展。     

双官能团大分子引发剂引发制备三嵌段共聚物

合成了以聚乙二醇400和聚氨酯预聚物为主体,两端各带有2-溴丙酰氧基的两种大分子引发剂,并以此分别对苯乙烯和甲基丙烯酸甲酯进行原子转移自由基聚合(ATRP),得到了PS-PEG-PS,PS-PU-PS,PMMA-PEG-PMMA,PMMA-PU-PMMA四种“大-小-大”三嵌段共聚物,用^1H-NMR、GPC、DSC、TGA分别对其进行了表征和检测。结果表明,两种大分子引发剂均能引发合成分子量可控、分子量分布较窄的嵌段共聚物,两种大分子引发剂对MMA的聚合速度明显高于St。热分析表明,三嵌段中的小嵌段,无论是较软的PEG-400或较硬的PU,均可使PS及PMMA的Tg有不同程度的下降。     

两嵌段共聚物PMMA-b-PHEMA的合成与表征

采用分步法合成了两嵌段共聚物聚甲基丙烯酸甲酯-b-聚甲基丙烯酸-2-羟乙酯.首先以AIBN为引发剂,FeCl<,3>/PPh<,为>催化体系,通过甲基丙烯酸甲酯(MMA)的反向原子转移自由基聚合,得到端基含Cl的聚合物PMMA-Cl,其分子量分布为1.36;然后以此为大分子引发剂,FeCl<,2>/PPh<,3>为催化...     

甲基丙烯酸三氟乙酰氧乙酯的聚合

对甲基丙烯酸三氟乙酰氧乙酯(TFAOEMA)的阴离子聚合及原予转移自由基聚合进行了研究。常用的阴离于引发剂如丁基锂、1，1-二苯基已基锂等很难引发TFAOEMA的阴离子聚合，而碱性较弱的引发剂如三乙基铝却容易引发，且产率较高。以氯化亚铜、五甲基二乙基三胺、溴代丙酸乙酯为引发体系的TFAOEMA的本体原子转移自由基聚合符合活性聚合特征。但在四氢呋喃为溶剂的原子转移自由基聚合中却存在活性中心失活现象。以末端含卤素的聚甲基丙烯酸甲酯为大分子引发剂，引发TFAOEMA的原子转移自由基聚合，得到了含氟双嵌段聚合物。     

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 ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.