DF-3740韧性氰酸酯/双马来酰亚树脂的性能

采用增容改性方法得到了DF-3740氰酸酯/双马来酰亚胺改性树脂,表征了未固化树脂的物理特性、固化反应性、耐热性能和力学性能等.DF-3740易溶于酮类溶剂,熔点62℃,熔融粘度低.在加入有机锡催化剂后,固化反应的最大放热峰由239℃降低至197℃.固化树脂具有双玻璃化转变温度(224.6,256.4℃),弯曲强度、弯曲模量以及冲击强度较纯氰酸酯固化树脂有大幅度提高,与5245C树脂接近.玻璃布复合材料的力学性能优于改性双马体系和环氧改性氰酸酯体系,表明DF-3740是一种高性能基体树脂.     

双酚A型二氰酸酯及其环氧改性体系的反应性研究

采用两种不同环氧树脂与双酚A型二氰酸酯树脂(BADCy)进行共聚改性,应用DSC,FTIR对BADCy及其环氧改性体系的反应机理及产物结构进行了研究,结果发现,BADCy在固化过程中仅发生自聚反应并生成三嗪环.环氧改性氰酸酯体系在低温下(＜180℃)主要发生氰酸酯自聚、嗯唑啉酮的生成及少量环氧醚化反应,而在高温下(＞200℃)主要发生噁唑啉酮结构的转变及环氧基的插入反应,并最终生成噁唑烷酮,固化体系中同时含有三嗪环、异氰尿酸酯、噁唑啉酮及噁唑烷酮环基团,各基团含量主要由改性体系中环氧基团的含量及固化温度决定.     

CTBN改性双酚A型氰酸酯树脂的性能

为改善氰酸酯树脂的冲击韧性,在双酚A型二氰酸酯(BADCy)树脂中混入了不同含量的端羧基丁腈橡胶(CTBN).用差示扫描量热法(DSC)及红外光谱法(FTIR)对CTNB/BADCy共混体系的反应性研究发现,CTBN能促进BADCy低温下的三嗪环反应,但是使BADCy的后处理温度提高.SEM分析表明,当CTBN的含量(质量分数)大于15%后,有CTBN颗粒从BADCy中析出,形成两相结构,且随着CTBN含量的增大,分散相的粒径增大,在断口处产生的银纹和剪切带使BADCy/CTBN共混体系的韧性提高.当CTBN的含量为25%时体系的冲击强度提高了2.3倍.     

海因环氧改性氰酸酯树脂体系的固化行为研究

目的 采用非等温差示扫描量热法（DSC）和傅里叶红外光谱（FT–IR）研究海因环氧/双酚A型氰酸酯（BAE）和海因环氧/四甲基双酚F型氰酸酯（TBF）的固化反应行为。方法 通过Kissinger、Ozawa和Crane法对2种树脂体系的固化动力学参数进行了计算，并采用热重分析（TGA）和热机械分析（DMA）评价树脂改性前后的热稳定性和热力学性能。结果 海因环氧改性氰酸酯树脂体系均呈现双重固化放热峰，TBF体系具有相对更高的表观活化能，而BAE体系具有更好的耐热性能，其玻璃化转变温度（tg）和在氮气下质量损失率为5%时的温度分别为271.6℃和403.4℃。结论 海因环氧树脂可以促进氰酸酯的聚合反应，制备的改性树脂体系可用于耐高温树脂基体和电子封装等材料。     

聚甲基丙烯酸甲酯@聚丁二烯核壳结构纳米粒子增韧双酚A型氰酸酯树脂性能

采用聚甲基丙烯酸甲酯（PMMA）@聚丁二烯（PB）核壳结构粒子增韧双酚A型氰酸酯（BADCy）树脂,制备了PMMA@PB/BADCy树脂。研究结果表明,当PMMA@PB质量分数为6wt%时,可以取得较好的增韧效果,PMMA@PB/BADCy树脂冲击强度达到了14.32 kJ · m^-2,提高了83.6%;DMA和TG-DTA耐热性测试结果表明,PMMA@PB的加入未降低树脂耐热性,固化后PMMA@PB/BADCy树脂的玻璃化转变温度为236.8℃,最大热分解温度为410.0℃。SEM和TEM结果表明,PMMA@PB核壳橡胶在BADCy树脂基体中分散性好,PMMA@PB/BADCy树脂破坏断面呈现典型的韧性破坏。PMMA@PB/BADCy树脂流变特性的测试表明,PMMA@PB核壳橡胶加入后基本没有影响到BADCy树脂的流变特性,PMMA@PB/BADCy树脂的最低点黏度为0.79 Pa · s左右,是树脂浸渍纤维的理想黏度。介电性能测试表明,PMMA@PB核壳橡胶增韧BADCy树脂后介电性能影响不大,当PMMA@PB质量分数为6wt%时介电常数为3.0,介电损耗为0.010。该PMMA@PB/BADCy树脂性能优异,可作为预浸料基体树脂,适用于航空航天低介电复合材料的制造。     

F-48环氧树脂改性双酚A型氰酸酯树脂的研究

采用FT-IR与DSC研究了F-48酚醛型环氧改性双酚A型氰酸酯树脂的固化行为及固化工艺,通过DMA、TGA、介电性能和冲击强度测试对F-48酚醛型环氧改性双酚A型氰酸酯树脂的热性能、介电性能和韧性进行了研究。结果表明,随着F-48环氧树脂含量的增加,改性氰酸酯的Tg总体呈升高趋势,最高达到255℃;改性后的氰酸酯树脂热分解温度逐渐降低;F-48环氧树脂加入量为氰酸酯质量的25%时,改性氰酸酯树脂具有较低的介电常数和介电损耗;改性氰酸酯的冲击强度较纯氰酸酯树脂提高25%。     

氰酸酯／双马来酰亚胺／环氧树脂三元共聚物及性能研究

采用双马来酰亚胺和环氧树脂与氰酸酯共聚对氰酸酯树脂进行改性，用FTIR跟踪了其固化过程。性能测试表明，当BCE：BMI：EP为5：2：3时，其固化物的冲击强度达到了12．2kJ·cm^-2，韧性有较大的提高；改性树脂的耐热性随着EP含量的增加而下降，当EP含量为30％时，Tg为233．7℃；改性后的氰酸酯树脂在1MHz频率下的介电常数和介电损耗角正切都比纯CE的有所增加，但上涨的幅度较小，仍具有优异的介电性能；DMA分析表明，在瓦温度时，损耗因子和损耗模量达到最大值，其中，tanδmax为0．359。     

环氧树脂改性双酚A型氰酸酯树脂的性能研究

通过DSC、DMA和TGA、介电性能测试和力学性能测试等方法,研究了环氧树脂用量和分子结构对氰酸酯树脂性能的影响。结果表明,环氧树脂改变了氰酸酯树脂的固化反应历程,降低了氰酸酯树脂的玻璃化转变温度、热分解温度和介电性能,提高了氰酸酯树脂的弯曲强度和冲击强度。含脂环和酯键的三官能团TDE-85树脂与JF-45邻甲酚甲醛环氧树脂相比,在改善氰酸酯树脂力学性能方面较好,在保持氰酸酯的耐热性和介电性能方面相当。     

短切玻纤增强PEKK与BDM/DABPA共混体系固化反应动力学及断裂韧性

利用二烯丙基双酚A(DABPA)对二苯甲烷型双马来酰亚胺(BDM)树脂进行扩链,采用短切玻纤增强聚醚酮酮(PEKK-GF)对BDM/DABPA树脂进行改性。利用差示扫描量热法(DSC)研究了PEKK-GF改性BDM/DABPA树脂固化动力学,确定了改性树脂的固化工艺,并计算出了改性树脂的部分动力学参数。改性树脂的力学性能通过万能拉力机进行测试,结果表明当BDM/DABPA体系中加入10%(质量分数)的PEKK-GF时,改性树脂固化物的冲击强度比原来体系提高了69%,临界应力强度因子(KIC)和临界应变能释放率(GIC)值分别为1.22 MPa·m0.5和295J/m~2,分别提高了21%和59%;拉伸强度从85.21 MPa增加到96.39 MPa,拉伸模量从4.198GPa增加到4.531GPa;弯曲强度从133.0 MPa增加到140.4 MPa,弯曲模量从4.080GPa增加到4.251GPa。采用动态热机械分析法(DMA)对改性树脂体系耐热性进行研究,结果表明,当BDM/DABPA树脂中加入10%(质量分数)的PEKK-GF时,改性树脂固化物的玻璃化温度提高了16.5℃,达到263.5℃。该改性树脂综合性能优异,在耐高温预浸料基体树脂及胶黏剂等领域具有很好的应用前景。     

卫星用M40/BADCy复合材料研究

为提高卫星结构用复合材料的性能,研制了改性氰酸酯树脂基M40复合材料,采用傅里叶红外光谱法及DSC法对E51环氧树脂改性双酚A型二氰酸酯(BADCy)体系的反应性进行了研究.结果表明:低温时主要发生三嗪环反应,高温时主要发生五元化反应;BADCy改性体系的吸湿率随E51含量的增加而下降,当E51含量为10%时,BADCy的弯曲强度和冲击强度分别提高了27%和49%;100h水煮使M40/BADCy复合材料的层间剪切强度下降18%,-50℃/12 h～150℃/12 h循环20次的高低温交变对M40/BADCy复合材料的力学性能几乎没有影响,经总计量为109J/m2的紫外线辐射后,M40/BADCy复合材料的剪切强度和弯曲强度仅下降了7.5%和9.1%.     

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.