调制式DSC研究聚乙烯的溶液结晶行为

采用调制式DSC研究了聚乙烯在溶液及熔体环境下的结晶行为、晶体可逆和不可逆热流的变化特点以及其与结晶度的关系。结果表明,聚乙烯不可逆热流表现为升温过程中部分结构单元的重结晶放热和增厚片晶的熔融行为;溶液结晶生成的晶体仍存有一定的介稳度,但其不可逆热焓值远远小于从熔体中形成晶体的不可逆热焓值。两种结晶方式结晶度的显著差别主要是不可逆热焓值差别的贡献。     

高压下液晶诱导聚合物伸直链晶体生成的研究

聚合物伸直链晶体一直是人们期望获得高强度、高模量材料中最引人注目的晶体结构,以往高压结晶获得聚合物伸直链晶体通常需要较高压力和温度的苛刻条件。本研究以液晶诱导制备含伸直链晶体的聚乙烯(PE)、聚酰胺(PA)及聚对幕二甲酸乙二醇酯(PET)等聚合物,使伸直链晶体的生成条件大幅度缓和．高压下液晶诱导生成聚合物伸直链晶体尝试成功,为其研究开辟了新的领域,同时也为聚合物伸直链晶体的工业化和实用化提供了新的途径和可能。文中同时介绍了液晶诱导聚合物伸直链晶体生成的两种机理,并提出了进一步研究的方向。     

PET/PC共混物配比对其高压结晶行为的影响

利用SEM及W AXD等测试手段研究了配比对PET/PC共混物高压结晶行为的影响。SEM观察表明,随PC比例的增加,共混物高压下主要结晶形态以伸直链晶体,生长成熟的立体开放球晶,大尺寸球晶的方式变化。拟合分峰法和W arren-A verbach傅氏分析法的计算结果表明,随PC含量的增加,高压结晶共混物的结晶度降低,PET的平均晶粒尺寸总体呈减小趋势,晶粒尺寸分布则变窄,而晶格畸变平均值在一定PC比例范围内达到极大值。     

UHMWPE初生态微观结构及不同成型条件下制品力学性能研究

超高分子量聚乙烯(UHMWPE)极高的分子量及线性分子链特性使其具备很多的优异性能,在军工、医药卫生等领域的应用越来越广泛的同时,对UHMWPE树脂的性能不断提出更高的要求。故利用高分辨扫描电镜(SEM)、高温凝胶色谱-红外联用(GPC-IR)、拉曼光谱(Raman)及差式扫描量热仪(DSC)对树脂初生态粒子的结晶结构、分子特性及热力学性能进行了研究,并通过控制模压过程中的冷却速率来研究UHMWPE样品的结晶行为,进而分析UHMWPE微观特性与宏观性能之间的关系。研究发现由次级颗粒和微纤组成的UHMWPE初生态粒子中具有大量的片晶和伸直链,分子链排列规整,结晶度高;但在熔融再结晶加工成制品的过程中,分子链的规整性遭到破坏,与初生态粒子相比,结晶度下降、缠结密度变大。另外,不同降温速率的样品中淬冷样品的分子链缠结密度最低,而低缠结、小的晶粒能够提升制品的耐冲击性能及断裂时的真应力。     

聚乙烯/蒙脱土复合材料的结晶行为

采用溶液共混法制备了聚乙烯(PE)／有机纳米蒙脱土(MMT)复合材料。首先利用广角X射线衍射(WAXD)及透射电镜(TEM)分析了复合材料的微观相态,然后采用DSC分剐对高和低MMT含量复合材料的结晶行为进行了研究。研究显示,MMT在PE基体中得到了较好的分散;在低MMT含量的复合材料中,MMT对聚乙烯结晶过程的影响是诱导成棱及阻碍分子链运动的协同作用;而在高MMT含量下,MMT并不影响聚乙烯的晶型及晶胞尺寸,但对其表现结晶度有较大影响。     

调制式DSC测定聚乙烯的结晶度

为探索和建立用DSC测量聚乙烯(PE)结晶度的标准方法．采用调制式DSC(MDSC)对不同PE的固有结晶度进行了分析和测定;研究了PE在熔融过程中可逆与不可逆热流所对应的可能的大分子结构及运动特征,根据实验确定的包括基线在内的测定方法精确测定了不同PE的固有结晶度．并与广角X射线衍射的结果进行了比较。     

自增强高性能聚合物的成型工艺同力学性能间相关性研究——5.自增强高聚物的起始熔点对超牵伸比和结晶形态的依赖性

本文从可结晶性聚合物缠结网或交联-缠结网的应力诱导结晶理论和高分子内旋转构象理论出发,研究了自增强高聚物的形变自由能对应力诱导结晶机理的依赖性,计算了两种晶型(伸直链晶和串晶)的自增强高聚物处于形变态和自由态下的形变自由能,得到了自增强高聚物的起始熔点同成型中牵伸比和温度、结晶形态和结晶度及非晶区中高分子链构象分数等间的定量关系式。并用该式分析了自增强聚乙烯的实验数据,证明理论同实验能较好的符合。     

STUDY ON THE RELATIONSHIP BETWEEN THE PROCESSING AND MECHANICAL PROPERTIES FOR SELF-REINFORCED POLYMERS——5.Dependence of Incipient Melting Temperature on the Draw Ratios and Morphology

本文从可结晶性聚合物缠结网或交联-缠结网的应力诱导结晶理论和高分子内旋转构象理论出发,研究了自增强高聚物的形变自由能对应力诱导结晶机理的依赖性,计算了两种晶型(伸直链晶和串晶)的自增强高聚物处于形变态和自由态下的形变自由能,得到了自增强高聚物的起始熔点同成型中牵伸比和温度、结晶形态和结晶度及非晶区中高分子链构象分数等间的定量关系式。并用该式分析了自增强聚乙烯的实验数据,证明理论同实验能较好的符合。     

自增强高性能聚合物的成型工艺同力学性能间相关性研究

本文从可结晶性聚合物缠结网或交联一缠结网的应力诱导结晶理论和高分子内旋转构象理论出发，研究了自增强高聚物的形变自由能对应力诱导结晶机理的依赖性，计算了两种晶型（伸直链晶和串晶）的自增强高聚物处于形变态和自由态下的形变自由能，得到了自增强聚物的起始熔点同成型中牵绅比和温度，结晶形态和结晶度及非晶区中高分子链构象分数等间的定量关系式。并用该式分析了自增强聚乙烯的实验数据，证明理论同实验能较好的符合。     

结晶度对聚乙烯热氧老化特性的影响

研究了结晶度对聚乙烯在80℃人工热氧老化条件下老化特性的影响,比较分析了不同老化时间其拉伸强度、拉伸模量和冲击强度的变化差异,考察了不同结晶度聚乙烯明度和整体色差变化的差别,采用衰减全反射红外光谱(ATR-FTIR)分析了三种不同结晶度的聚乙烯在老化过程中羰基指数、羟基指数、断链程度、结晶度等微观结构参数的变化趋势。结果表明:在80℃热氧老化环境条件下,随着老化时间的延长,结晶度越高聚乙烯的拉伸性能下降越明显,抗冲击性能的下降越缓慢,明度和整体色差的变化越快,氧化与断链作用更剧烈,其中氧化集中在老化后期,断链主要发生在老化初期,聚乙烯更容易老化。在整个老化周期里,不同结晶度聚乙烯的结晶度均呈现先上升后基本不变的趋势,但是聚乙烯的结晶度越低热老化对其结晶度的影响越大,增大幅度越剧烈。     

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.     

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...     

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.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

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.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.