PU(HTPB)/P(MMA-co-EGDMA)同步互穿网络的合成、形态与力学性能

研究了 PU(HTPB)/P(MMA-co-EGDMA)-IPN 的合成、形态和力学性能。结果表明,两网络的相对形成速率对 IPN 的形态和性能有显著的影响。当两网络形成大致同步时,微区尺寸适中,界面互穿良好,IPN 的综合力学性能最佳。两网络交联密度对 IPN 的力学性能也有显著影响,但只有先形成的网络的交联密度变化才会引起形态的明显改变。     

聚醚型聚氨酯/超支化聚酯互穿聚合物网络的形态和力学性能

为了改善聚醚型聚氨酯弹性体(PU)的力学性能,运用互穿聚合物网络(IPN)技术,分别将端正己烷基、端十二烷基、端十八烷基超支化聚酯(HBP-C6、HBP-C12、HBP-C18)引入至PU中形成共混体系。结果表明,相比于空白胶片,PU/HBP IPN体系的力学性能有了一定的提高,超支化聚酯端烷烃链越长,相畴尺寸逐渐减小,互穿程度更高;高含量的HBP-C18加入后,随着其质量分数的增加,互穿网络胶片的拉伸强度和断裂伸长率均呈现出先增大后减小的趋势,加入30%的HBP-C18时,形成了双相连续的微观结构;采用"准一步法"和"一步法"合成端十八烷基超支化聚酯,分别与聚氨酯形成互穿网络,力学测试结果表明,前者的力学性能优于后者。     

聚丁二烯型聚氨酯/聚(苯乙烯—二乙烯苯)互穿聚合物网络的力学性能

聚丁二烯型聚氨酯与聚醚型或聚酯型聚氨酯比较,力学性能较低,因而推广应用受到一定的限制。加入炭黑和其它填料,虽能在不同程度上改进力学性能,但会引起体系粘度增大和混炼、浇注困难。我们曾报道用同步法合成聚丁二烯型聚氨酯/聚(苯乙烯—二乙烯苯)互穿聚合物网络〔PU(HTPB)/P(St-DVB)-IPN〕,并研究了该 IPN 体系的     

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。     

蒙脱土改性PU/EP IPN的研究

本文通过端异氰酸酯基聚氨酯预聚体与环氧树脂E-51形成了互穿网络,并通过热重分析仪(TGA)研究了完全固化后的互穿网络的热分解行为;透射电镜研究了IPN的相分离行为及用拉伸强度,断裂伸长率对其进行了力学性能的表征.结果表明,经过环氧树脂改性的聚氨酯的耐热性能比纯聚氨酯得到了提高,且力学性能也有所改善.并选取性能较好的PU/EP IPN,用纳米级有机蒙脱土对其进行了改性.研究发现,经有机纳米蒙脱土改性的PU/EP IPN的力学性能及耐热性有了进一步的提高.     

梯次化聚氨酯/乙烯基酯树脂IPN的结构及阻尼性能

采用同步互穿和梯次化涂层工艺,室温固化制备新型梯次化聚氨酯/乙烯基酯树脂(甲基丙烯酸丁酯)互穿聚合物网络(PU/VER(BMA)IPN).采用DMA考察了涂层时间间隔和组成比对阻尼性能的影响.结果表明当涂层时间间隔为3h,组成比为50/50～60/40～70/30的梯次化IPN材料,tgδ＞0.3的温域为-57～90℃,tgδ＞0.5的温域为-36～54℃,其有效阻尼温域较单层材料的明显变宽.SEM-EDX对材料梯度结构的检测结果表明制备的梯次化IPN材料宏观组成上存在梯度结构;存在独立的组成和结构均匀的各层结构;层间过渡区域为组成连续变化的梯度结构.TEM检测结果表明材料的梯度区域较每层区域具有更加精细、均匀的双相连续微观结构.并且通过梯次化涂层工艺使材料的力学性能得以改善,涂层综合性能较好.     

PU/PMMA IPN的分子运动与交联密度的研究

用顺磁共振波谱仪(ESR),以4-羟基-2,2,6,6-四甲基哌啶嗣(TEMPOL)作自旋标记,测定了不同组成及不同温度聚醚聚氨酯/聚甲基丙烯酸甲酯(PU/PMMA)互穿网络聚合物(IPN,S)的分子运动与互穿缠结程度的关系。实验结果表明:在该IPN中两网络互穿缠结程度越大,在高场上出现各向同性温度T_n越高。当PU/PMMA=40/60时,得到较大交联密度和较高温度的T_n。由测得的T_(50G)温度看出该体系是两相分离体系,并且不同组成比的IPN两个T_(50G)温度发生内移,在40/60时内移最大,用动态力学方法测得的结果与此一致。     

PU／P（MA—DMA）／EP三组分IPN力学性能的研究

用同步法合成聚氨酯/聚(丙烯酸甲酯-甲基丙烯酸β-N,N′-2-甲基乙酯)/环氧树脂三组分互穿聚合物网络,对IPN组成、结构与性能的关系进行了讨论。结果表明,改变组成比可以得到相容性不同的IPN。本文认为组成比对IPN性能的影响较连续相为大,加入接枝剂可以有效地改变IPN的相容性。力学性能与组成网络的结构及缠结方式有关,组成比相同时,全IPN具有较大的应力值。加入填料,体系中发生“准交联”作用,使阻尼值增高,转变温度区域加宽。     

HTBN型聚氨酯/聚丙烯酸酯阻尼材料的合成及性能研究

以端羟基聚丁二烯/丙烯腈共聚物(HTBN)为软段,甲苯二异腈酸酯(TDI)为硬段的聚氨酯预聚体,以丙烯酸酯单体为自由基聚合单体,利用"同步互穿"工艺,制备了一系列室温固化HTBN型聚氨酯(HTBN-PU)/聚丙烯酸酯(PA)互穿网络(PU/PA-IPN)聚合物.研究表明:二月桂酸二丁基锡(T-12)用量为0.3%、过氧化苯甲酰(BPO)用量为1.0%时,PU/PA两相可形成较为理想的阻尼IPN结构.以甲基丙烯酸丁酯(BMA)为PA相的PU/PA-IPN材料阻尼性能最好,tanδ＞0.3的温域高达126℃(-46～80℃),tanδ的峰值为0.85;PU/PA-IPN的频谱图表明,材料表现出较好的低频(10Hz)阻尼性能.     

聚氨酯/环氧树脂互穿聚合物网络半硬泡沫的结构与性能

采用同步法合成了聚醚型聚氨酯/环氧树脂互穿聚合物网络半硬泡沫.通过FTIR,DMA,SEM研究了IPN半硬泡沫的化学结构、动态力学性能以及微观结构形态.FTIR分析表明了聚氨酯和环氧树脂的网络间存在接枝反应.很宽组成比范围内IPN半硬泡沫均显示出单一的宽温域玻璃化转变,而且该转变随着环氧树脂含量的增加向高温方向移动.通过SEM发现IPN半硬泡沫泡孔结构形状都比较均一.循环加载压缩发现所有IPN泡沫不仪压缩性能好而且具有很好的回弹性,大变形压缩后泡沫儿乎不变形,重复使用性能好.     

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 ...