一锅法和两步法合成脲-异丁醛-甲醛树脂的结构与性能

以脲、异丁醛和甲醛为原料,硫酸为催化剂,采用"一锅法"和"两步法"合成了脲-异丁醛-甲醛(UIF)树脂,并利用红外光谱(FT-IR)、凝胶渗透色谱(GPC)、热失重(TG)等手段对其结构和性能进行了研究。结果表明,在合成UIF树脂过程中,异丁醛上的α氢原子和脲中的胺基氢原子均参与Mannich反应;"两步法"合成的UIF树脂产率、软化点及分子量较高,分子量分布较窄,副反应少,而"一锅法"合成UIF树脂的耐热性较好,羟基值较高;两种方法合成的UIF树脂均具有优良的耐热黄变和抗紫外光性能。     

可UV固化脲-异丁醛-甲醛树脂的合成与表征

以异佛尔酮二异氰酸酯(IPDI)、丙烯酸羟乙酯(HEA)改性脲-异丁醛-甲醛树脂(UIFR),通过两步法合成了一种含碳碳双键可紫外光(UV)固化的脲-异丁醛-甲醛树脂(UVUIF)。研究了反应温度和催化剂用量对反应的影响。适宜的反应条件为:第一步反应温度70℃,催化剂用量0.10wt%;第二步反应温度60℃。通过红外光谱分析,证明了合成的UVUIF结构中已引入了光敏性的碳碳双键。经UV辐射固化后,固化膜仍具有较好的热稳定性、硬度和附着力。     

N-甲基-2-(4-羟基苯基)[60]富勒烯吡咯烷衍生物的合成研究

利用肌氨酸和对羟基苯甲醛所形成的亚胺叶立德与C60发生 1,3-偶极环加成反应,合成了一种新型含羟基C60吡咯烷衍生物:N-甲基-2-(4-羟基苯基)[60]富勒烯吡咯烷.通过UV-vis、1H-NMR、MS、FT-IR确定了产物的结构.探讨了反应条件对产物产率的影响,得到了最佳工艺条件:反应物摩尔比为1:2:6,温度为90℃,反应时间为5h,此时产物的产率可达到87%(以消耗的C60计).     

影响酚醛型苯并口恶嗪软化点的结构因素

合成了分子量不同的酚醛树脂预聚体,以此为多元酚基体采用悬浮法通过控制苯酚与苯胺的摩尔配比合成了一系列苯并口恶嗪环状结构含量不同的酚醛型苯并口恶嗪中间体树脂(P-BOZ),并用FT-IR和1H-NMR对其结构进行了表征,用环球法对其软化点进行了测量。研究表明,P-BOZ的软化点随酚醛树脂预聚体分子量的增加而提高,随苯并口恶嗪环状结构含量的增加而降低,这一现象与分子间酚羟基的氢键作用有关。因此,通过分子设计可以提高其软化点。     

N,N,N-三甲基-1-金刚烷基季铵盐的合成

以金刚烷胺为原料,通过艾希魏勒-克拉克反应(Eschweiler-Clarke)合成了N,N-二甲基金刚烷胺,优化反应条件为金刚烷胺∶甲酸∶甲醛的摩尔比为1∶5∶4,反应时间为18h,温度为98℃,产物收率93.4%,进而合成了N,N,N-三甲基-1-金刚烷基季铵盐,产物收率90.5%,其结构经1H-NMR,13C NMR,MS和GC-MS表征。     

具红外隐身功能石蜡微胶囊制备工艺研究

探讨了以脲、甲醛、三聚氰胺聚合物包覆普通石蜡微胶囊化的工艺,力求实现其在红外隐身上的效果,得出实验室最优工艺条件为:(1)以脲∶甲醛∶三聚氰胺摩尔比为1∶3∶1,pH值8～9,60℃水浴0.5h制备预聚液;(2)以十二烷基苯磺酸钠为乳化剂,添量为5%,3000r/min转速下,15min制备相变乳液;(3)固化条件为pH值约4.5,70℃水浴,反应时间1.5～2 h.所得微胶囊经红外、DSC测试,结构完整,相变热略低于石蜡,相变温度则稍有上升.     

甲醛改性松香环氧树脂的制备和性能

以松香和甲醛为原料,在催化剂作用下发生Prins加成反应,合成了甲醛改性松香;再与环氧氯丙烷发生开环反应、闭环反应,合成了甲醛改性松香环氧树脂。用红外光谱(FT-IR)、核磁共振谱(~1H-NMR)和凝胶渗透色谱(GPC)等对产物进行了表征。在适宜的条件下,合成的环氧树脂的环氧值为0.37 mol/(100 g)。采用固化剂4,4'-二氨基二苯砜(DDS)和甲基六氢苯酐(MHHPA)对产物进行了固化。DSC和TG表明,甲醛改性松香环氧树脂/DDS固化物具有较好的热性能。     

微甲醛含量脲醛树脂的制备

尿素和甲醛为原料,三聚氰胺/多羟基添加剂复合体系为甲醛捕捉剂制备了微甲醛含量的脲醛树脂。甲醛/尿素(F/U)物质的量比增大,脲醛树脂中的游离甲醛含量上升、树脂黏度下降。分别增加三聚氰胺和多羟基添加剂用量,脲醛树脂中的游离甲醛含量降低、树脂黏度增大。当甲醛/尿素物质的量比为1.06,三聚氰胺用量为1%(质量分数,下同),多羟基复合添加剂用量为1.5%时,以及采用一次性加入甲醛和三聚氰胺、分批次加入尿素和多羟基添加剂的合成工艺与相应条件,制备的脲醛树脂中的游离甲醛含量低于10 mg/kg,远低于欧洲的E1级指标。     

六官能UV固化脲-异丁醛-甲醛树脂的合成

脲-异丁醛-甲醛树脂(UIF)是一种效果显著的涂料助剂,可以改善涂膜的硬度、光泽和附着力等性能。将其应用在光固化涂料体系中,因其分子结构不含能固交联固化的活性基团,无法参与固化成膜,所以固化膜的耐溶剂性与耐化学试剂性较差。以硼氢化钠、异佛尔酮二异氰酸酯(IPDI)、季戊四醇三丙烯酸酯(PETA)改性UIF,通过预封端法制备了六官能UV固化脲-异丁醛-甲醛树脂(UVUIF)。对反应温度和催化剂用量进行了探讨与研究。该树脂具有良好的热稳定性。添加到涂料中,可以改善涂膜附着力、硬度、光泽度,减少光固化时间。     

淀粉基吸水树脂的制备与性能分析

以淀粉、丙烯酸(AA)和丙烯酰胺(AM)为原料,采用过硫酸铵[(NH_4)_2S_2O_8]作为引发剂,利用N,N-亚甲基双丙烯酰胺(NMBA)进行交联,采用水溶液聚合法制备了AA-AM共聚淀粉吸水树脂。考察了丙烯酸溶液pH、丙烯酸单体用量、引发剂及交联剂用量、反应体系温度与时间对合成树脂性能的影响。通过性能测试和分析得出优化合成条件为:丙烯酸溶液pH=5.5,丙烯酸单体与葡萄糖剩基(AGU)摩尔比为7∶1,过硫酸铵用量为0.35mmol,交联剂用量为0.08571mmol,反应时间为65℃,反应温度为3h。在优化工艺下合成的树脂吸收蒸馏水、0.9%NaCl溶液量分别达到798.6g/g和95.7g/g。采用红外光谱(FT-IR)和热重分析(TG)对合成的树脂进行了表征与分析评价。     

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.