Secondary electron emission from polymers and its application to the flexible channel electron multiplier

The basic characteristics of secondary electron emission (SEE) from various organic compounds have been investigated, and a channel electron multiplier with high gain and flexibility has been developed. The maximum SEE yield is higher for the aliphatic compound than for the aromatic, and is higher for the organic solid with high ionization potential. By studying the SEE yields from the electron-conductive polymeric compositions which consist of plasticized poly(vinyl chloride) and electroconductive particles (NaTCNQ or carbon black), it is shown that the SEE yield depends mainly on the characteristics of the matrix polymer and is almost independent of the addition of electroconductive particles which inherently have low SEE yields. Adding less than 5% stabilizers to these polymeric compositions has little effect on the SEE yields. A flexible channel electron multiplier (FCEM) made of the electron-conductive polymeric composition shows the following characteristics: gain ? 10⁸ (applied voltage of 3 kV); rise time ? a few nanoseconds; background count rate < 0.1 cps; and maximum output current ? 10^?6 A. As a photon detector in the vacuum UV region, the FCEM shows a threshold value of 8.4 eV for photoelectric emission.     

Polymer chains in semidilute solutions confined to a square channel: mean-field Gaussian chain theory and comparison with simulation results

We extend the mean-field Gaussian chain theory, originally developed for non-dilute solutions of athermal polymer chains in a slit, to solutions in a channel with a square cross section. The formulation allows one to calculate the monomer density profile, the chemical potential of the confined polymer chain, and therefore the partition coefficient. For the mean-field potential, we used the first-order approximation that neglects local monomer density fluctuations and the second-order approximation that takes into account the fluctuations. The results of the density profile and the partition coefficient were compared with those obtained in the lattice Monte Carlo simulations. The theoretical results obtained with the first-order approximation agreed well with the simulation results for chains of 100 beads below the average monomer density of ca. 0.2. At higher concentrations, the second-order results gave a better agreement. This cross over indicates a change in the interactions between polymer chains from those in one-dimension to those in three-dimensions as the correlation length in the confined solution becomes sufficiently shorter than the channel width.     

三角槽道低 Reynolds 数脉动流与柔性壁耦合特性研究

以水为工质对三角槽道低 Reynolds 数脉动流与柔性壁耦合特性进行了实验研究。通过传热与流动实验,分析了脉动频率(W)、脉动振幅(A)、柔性壁特性对脉动流传热及流动的影响。同时,通过可视化实验,研究了柔性壁与脉动流之间的响应特性,解析了柔性壁形变与振频对脉动流传热及流动的作用机制及分离贡献。研究结果表明,柔性流道脉动流可以实现强化传热与流动减阻双重效果,但强化传热效果相对较弱(传热效率提升0~50%),适用于以减阻为主要目的的换热场合;柔性壁减阻与削弱强化传热效率,源于柔性壁形变造成时均流通截面积增大(流体流速下降)、W与A的增大减弱脉动能量;W的增加将使得柔性壁振动对脉动流强化传热效率的削减逐步趋于主导地位,而A的增加将使得柔性壁变形对脉动流强化传热效率的削减逐步趋于主导地位;脉动流阻力的削减主要来自于柔性壁的变形(D₁>70%),而柔性壁振频对于脉动流能量耗散的抑制作用较为次要。     

Graphene-Based Polymer Composites and Their Applications

Recently, graphene has attracted both academic and industrial interest because it can produce a dramatic improvement in properties at low filler content. The utilization of graphene-based materials in the fabrication of nanocomposities with different polymer matrixes has been explored. This review article presents and discusses the development of graphene-based polymer composites and their applications in different fields such as electronics devices, energy storage, sensors, ESD and EMI shielding and biomedical applications.     

GMA功能化聚合物及其在共混改性中的应用

通过熔融接枝、乳液聚合、溶液聚合、悬浮聚合等方法可以制得甲基丙烯酸缩水甘油脂功能化的共聚物，这些接枝、嵌段、核壳结构共聚物可以用作增韧剂和增容剂，通过“原位”反应增韧聚合物和增容聚合物共混物，提高聚合物的韧性和改善改善共混物的相容性。     

高聚物界面及其改性

介绍高聚物界面的概念,其基本参数的定义及测定方法。以界面理论为指导,详细阐述等离子体处理、接枝共聚等界面改性途径和国内外研究的最新成果。     

Transverse tensile characteristics of fiber composites with flexible resins: Theory and test results

A theoretical and experimental investigation has been conducted of the transverse tensile properties of flexible-resin/ glass-fiber composite lamina. The objective is to increase the elongation at failure of a lamina in a state of transverse tension so that when a lamina is used in a laminate configuration, it does not suffer premature failure (e.g., failure at a lower strain level than that for a lamina in fiber direction tension). We show that the mode of failure in the transverse tensile lamina differs greatly from that in the neat resin. The failure mode in the lamina form is found to be brittle fracture. From this, it follows that the controlling neat resin property is the low elongation modulus rather than the elongation at failure. Significant improvements in the transverse tensile strain at failure were obtained for the flexible-resin/glass-fiber systems studied.     

聚合物典型燃烧测试方法及其比较

文章阐述了聚合物阻燃理论的基本原理.对用于评价燃烧性能的主要阻燃特性和极限氧指数法、UL 94法、锥形量热仪法这三种典型测试方法做了介绍和比较.最后,展望了未来发展趋势.     

聚合物分离膜接枝改性技术及应用

介绍了化学、等离子体、辐射和光化学等应用于聚合物分离膜领域的接枝技术的主要特点。对接枝技术在聚合物分离膜的制备、改性、功能化和高性能化等领域的应用进行了总结。     

用于燃料电池的聚合物电解质膜及其改性方法

聚合物电解质膜是质子交换膜燃料电池的核心部件.目前广泛使用的全氟质子交换膜(如Nafion(R)系列)存在着价格昂贵、使用温度有限、甲醇渗透率高以及降解再生困难等缺点.对聚合物基质材料进行物理或化学改性,可以提高质子传导率、改善机械强度等性能,获得高性能、低成本的质子交换膜.从聚合物材料改性的角度,综述了燃料电池用聚合物电解质膜的制备方法和电化学性能,并对各种改性方法进行了比较.     

Polymer blend containing a thermotropic polyester with long flexible spacer in the main chain

Polymer blends of nylon 66 and thermotropic polyester with long flexible spacers in the main chains were prepared by melt mixing. The samples were made as single filaments by passing the polymer blend through a small and round die of a capillary rheometer. Mechanical properties of blends showed that the modulus and strength of nylon 66 could be improved without reduction of extensibility. The morphology of fractured surfaces was observed by a scanning electron microscope (SEM). It showed that the microfibrillar structure of a thermotropic polyester was formed by extensional flow while the spherical and ellipsoidal particles in the nylon 66 (matrix polymer) were produced by shear flow. The polyester particles were occasionally covered with adhering matrix polymer because of good adhesion between these two polymers. They were highly elongated by tensile stress without loss of elongational characteristics of blends. This fact was explained by very good adhesion between the two phases.     

柔性聚合物电解质的制备及其电化学性能

以不同质量比的丙烯酸甲酯(MA)和丙烯腈(AN)为单体,聚乙烯醇(PVA)为分散剂,采用绿色环保的改性乳液聚合法制得聚合物乳液,将聚合物乳液流延涂布制得柔性聚合物膜,进一步采用电解液浸润法制得系列柔性聚合物电解质膜(S1、S2、S3和S4)。通过傅里叶红外光谱仪(FTIR)、扫描电镜(SEM)、力学性能测定、热分析、交流阻抗(EIS)和充放电测试对材料的物理化学性能进行了表征。结果表明:当m(MA)∶m(AN)=23∶2(S2)时,聚合物膜的抗拉强度为14.3 MPa,断裂伸长率为248%,25℃时的离子电导率为0.95m S/cm。分别以LiCoO_2为正极、金属锂为负极,天然石墨为正极、金属锂为负极制备CR2032扣式锂离子电池并测试其循环伏安性能和充放电性能,4次循环伏安测试发现峰电位均无明显变化,0.1 C倍率下,首次放电比容量分别为142和307 mA·h/g,50次循环后分别为135和323 m A·h/g,1.0 C倍率下,LiCoO_2的放电比容量为134.3 mA·h/g,说明所制备的材料具有较好的电化学性能。     

分离膜高分子材料及进展

膜材料是膜分离技术的关键。本文主要介绍了具有重要应用和发展前景的5类高分子膜材料纤维素膜材料、聚酰亚胺膜材料、有机硅膜材料、液晶复合高分子膜材料、高分子金属络合物膜材料。内容涉及结构、性能、改进方法、用途等。     

The analysis of OPC pastes: A comparison between analytical electron microscopy and electron probe microanalysis

The chemical compositions of two 5 year-old OPC pastes with w/c 0.3 and 0.6 have been investigated by Analytical Electron Microscopy and Electron Probe Microanalysis. Comparison of the distributions of Ca/Si ratios of C-S-H obtained by the two methods gave good agreement, although Microprobe analyses of bulk samples may contain contributions from regions other than C-S-H.     

Polymer electrolyte membrane with nanomatrix channel prepared by sulfonation of natural rubber grafted with polystyrene

High‐proton‐conductive polymer electrolyte with a nanomatrix channel was prepared by graft copolymerization of styrene onto deproteinized natural rubber followed by sulfonation with chlorosulfonic acid. First, natural rubber latex was purified with urea in the presence of surfactant to remove almost all proteins present in the rubber. Second, graft copolymerization of styrene onto deproteinized natural rubber was carried out with tert‐butyl hydroperoxide/tetraethylenepentamine as an initiator at 30°C in latex stage. The graft‐copolymerized natural rubber (DPNR‐graft‐PS) was sulfonated with chlorosulfonic acid in chloroform solution at an ambient temperature. The resulting sulfonated DPNR‐graft‐PS was characterized by FTIR spectroscopy, solid state ¹³C CP/MAS NMR spectroscopy, elemental analysis, and transmission electron microscopy. High proton conductivity of about 0.1 S/cm, less water uptake of 24 wt % and comparatively good stress at break of 9 MPa were accomplished at suitable contents of styrene units and sulfur, i.e., 32 wt % and 75 mol %, respectively. The high proton conductivity, excellent stability, and good mechanical properties were associated with not only the formation of the nanomatrix channel but also a specific concentration of sulfuric acid group. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

含能高聚物粘结剂及其在炸药中应用的研究进展

对现有的含能高聚物粘结剂进行了分类,对其性质进行了归纳,总结了其在炸药中的应用,并指出了今后研究中应注意的问题.     

共混产品性能及用途综述

综述了近年来国内外专利中出现的新型共混产品的性能及用途，内容涉及热塑性塑料、工程塑料、热塑性弹性体和液晶聚合物等。     

石墨烯与导电高分子复合材料及其电学性能研究进展

石墨烯作为单原子厚度的二维碳原子晶体,是具有优异的力学、热学、电学性能的新型纳米复合填料。近年来,石墨烯材料在化学和物理学界引起广泛关注。论述了石墨烯与导电高分子复合材料的制备,并对其在超级电容器、太阳能电池以及电化学传感器方面的应用。     

Viscous flow of a Newtonian fluid in a curved channel with flexible moving porous walls

We consider flow of a viscous Newtonian fluid in a curved channel with moving porous walls; the upper wall is flexible and its position in unknown a priori. This work is motivated from a papermaking application namely roll forming. We solve the leading order terms in equations of motion using perturbation methods and present analytical expressions for the variation in channel size, pressure, and viscous shear. The stability of the solution is also examined and we report the conditions for marginal stability.