Development of a packaging material using non‐bleed‐type antistatic ionomer

Generally, plastics and plastic films are low in moisture absorption and high in electric insulation. They are inherently vulnerable to static charge build‐up, which can result in a variety of problems. We have developed a functional packaging material to solve these static problems, by using a potassium salt of ethylene ionomer, which is a non‐bleed‐type antistatic agent. Good antistatic performance was shown by evaluating a variety of electric characteristics (e.g. the static decay time, ash test and saturated electrostatic charge and half‐life) and surface resistivity. In addition, antistatic performance was achieved on the mLLDPE (non‐treated) side in a multilayer structure. This means that the use of potassium ionomer on any layers in a multilayer structure provides antistatic performance, leading to the expectation of developing a wide variety and diversity of packaging materials. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of ionomer thickness on mode I interlaminar fracture toughness for ionomer toughened CFRP

Effect of ionomer thickness on mode I interlaminar fracture toughness was investigated for the ionomer-interleaved CFRP. Laminates were fabricated with Toho UT500/111 prepregs. Ethylene-based ionomer, which has high ductility and good adhesion to epoxy resin, was used as an interleaf material in this study. Thickness of the ionomer film selected was 12, 25, 100 and 200 μm. EPMA analysis showed the existence of the interphase region between the interleaf film and the base prepreg lamina where ionomer and epoxy were mixed. Mode I fracture toughness tests were carried out using DCB specimens. Precracks were introduced into all of the specimens. Fracture toughness values were much improved by interleaving the ionomer films. The fracture toughness value increased sharply by inserting thin ionomer film; however, the additional increase with the increase of the ionomer thickness was smaller. The thickness effect of the ionomer interleaf differs from that of the other kinds of thermoplastic-interleaf. Microscopic observation revealed that the crack path depended on the thickness of the ionomer region. Crack propagated in the interphase/ionomer interfaces for thinner-ionomer-interleaved CFRP, and in the interphase region, at the interphase/base lamina interface and interphase/ionomer interface for thicker-ionomer-interleaved CFRP. Ionomer resin deformed largely only near the crack surfaces, and this fact is responsible for the nonlinear increase of the fracture toughness with the increase of the ionomer thickness.     

银盐印刷胶片的抗静电方法

银盐印刷胶片对抗静电剂的要求是不能影响卤化银的照相性能,不能破坏胶片的防粘连、防染料转移的特性,并且自身无色透明。抗静电剂可以分为导电型(离子导电型、电子导电型)物质和抑制静电荷产生的物质两大类。离子导电依赖环境湿度,有诸多缺陷:吸收潮气、寒冷干燥条件下失效等;电子导电不受外界影响,但在掺杂使用时,用量与胶之比要求最小临界量。但电子导电型抗静电剂自身固有颜色,或黑或蓝,都是印刷胶片所不能允许的。抑制明胶产生电荷的物质主要是含氟聚合物,能够调整明胶层的起电电序,在摩擦过程中,抑制胶片产生静电。含氟表面活性剂由于相对与乳剂容易混溶,从而成为优选的印刷胶片抗静电剂。     

Simulation of the effects of space charge and Schottky barriers on ferroelectric thin film capacitor using Landau Khalatnikov theory

The role of space charge induced in a ferroelectric thin film and the presence of Schottky barriers at the two electrode/film interfaces are studied by numerical simulation using Landau-Khalatnikov theory. In this work, the whole film is considered as the stacking of dipolar layers, each of which contains multilayers of perovskite cells. In the presence of a local electric field, the double-well thermodynamic potential of each layer is modified in an asymmetric manner. The local electric field distribution is determined both by the space charge and the boundary conditions imposed by the Schottky barrier heights. Asymmetric and skewed hysteresis loops are generated     

含碳纳米管的新型抗静电纤维的制备和性能

将多壁碳纳米管分散在自制的抗静电载体PR-86中制备出新型、高效和耐久的抗静电母粒．抗静电母粒的添加量仅为0．5％就可以制备出性能优良的“基体-微纤”型抗静电PP纤维．该纤维的抗静电机理为异极性大分子放电机理．多壁碳纳米管的存在增强了微纤相的极化程度和抗静电母粒的抗静电效果．抗静电纤维的抗静电性具有耐久性．抗静电母粒对纤维的性能基本上没有影响．     

Synthesis and characterization of composites of DBSA-doped polyaniline and polystyrene-based ionomers

The synthesis of composites of n-dodecylbenzene sulfonate-doped polyaniline (PANI-DBSA) and poly(styrene–metal acrylate) ionomers is presented. The ionomers of lithium, sodium and potassium were prepared by emulsion polymerization at different styrene-to-metal acrylate weight ratios. The composites made with the potassium ionomer exhibit the largest conductivity due to the higher content of acid groups that allows stronger interactions with the PANI chains compared to the Na and Li ionomers. IR spectroscopy suggests that hydrogen bonding interactions take place between PANI-DBSA chains and that amine salt groups form by chemical reactions between the amine groups of PANI and the acid groups of the ionomer. X-ray diffraction reveals that the ionomer affects the structural ordering of PANI-DBSA. All the PANI-DBSA–ionomer composites show higher thermal stability than the PANI-DBSA material. SEM shows a characteristic agglomerate morphology in all the composites. The composite showing the highest electrical conductivity was mixed with poly(n-butyl methacrylate) (PBMA) by extrusion and the films obtained have higher electrical conductivity than that of films of the same system without ionomer.     

Using the electrooptic effect to study charge relaxation in colloidal solutions of magnetite

The kinetics of birefringence in a colloidal system of magnetite particles in kerosene under the action of a pulsed electric field has been studied using an electrooptical cell with electrodes covered by a thin insulating film. Rectangular pulses of the field induce jumps in the birefringence signal (at the moments of field switching on and off), which are related to relaxation of the charge formed in the near-electrode region. Experimental data are used to evaluate the characteristic time of near-electrode space charge formation.     

染料敏化太阳能电池光阳极TiO2薄膜的研究进展

在概述染料敏化太阳能电池工作原理基础上,着重分析电池光阳极TiO2薄膜的特性,并指出该薄膜在电池中所起的作用:负载染料、收集光生电子、分离电荷和传输光生电子;继而从表面修饰、离子掺杂、量子点敏化、制备复合薄膜、设计微观有序空间结构、设计核壳结构以及多手段共改性等方面对TiO2薄膜改性手段进行综述,并详细分析改性手段优化染料敏化太阳能电池性能的原因;最后,提出应把优化光阳极TiO2薄膜制备工艺及探讨薄膜接触面工作机理等作为今后的研究重点。     

A numerical algorithm for simulation of the electric corona discharge in the triode system

A numerical algorithm is described to calculate the charge density, electric field and corona current distribution in the corona triode. The algorithm employs a hybrid technique based on the Boundary and Finite Element Methods (FEM). FEM is used to determine the electric field because of free space charge produced by the corona discharge. The Boundary Element Method (BEM) is applied for calculating the other component of electric filed as a result of the voltage applied to the electrodes. The Method of Characteristics (MOC) is used to update the space charge density distribution. The characteristic lines are traced backwards from points of the analysed domain to the corona wire. The current density, electric field and space charge density distributions can be controlled by changing the configuration of the system. Results of calculations in a few different cases show the influence of different parameters on the work of the corona triode.     

Electron emission from Pb(Zr0.65Ti0.35)O3 film cathode by pulse electric field

Pulse electric field induced electron emission from the Pb(Zr_0.65Ti_0.35)O₃ ferroelectric films has been investigated as a function of the film thickness from 0.2 to 4.0 μm and the upper electrode diameter from 200 to 1100 μm. The electron emission charge from the 3.0 μm film was several nC per pulse, which was comparable to that of the bulk ferroelectrics. However, the local dielectric breakdown occurred in the films below 1.0 μm without the electron emission, which was confirmed by the optical microscopy observation after the emission tests. As the upper electrode size decreased and the film thickness increased, electrons were more easily emitted without breakdown.     

Cover Picture: Microscopic Evidence for Spatially Inhomogeneous Charge Trapping in Pentacene (Adv. Mater. 11/2005)

Trapped charge has been observed in polycrystalline pentacene films by electric force microscopy in work reported by Muller and Marohn on p. 1410. The cover shows an optical fiber watching the motion of a metal‐coated cantilever hovering over a polycrystalline pentacene film. The film occupies the 6.5 μm gap in a working field‐effect transistor. Trapped charge (dark blue and black areas in the pentacene) appears as large patches randomly distributed throughout the device, implying that long‐lived traps in polycrystalline pentacene are not correlated with grain boundaries.     

Preparation and characterization of durable antistatic polyurethane elastomer by preirradiation grafting on its film

Polyurethane (PU) film gave birth to free radical by ⁶⁰Co-γirradiation under nitrogen atmosphere, and then the film was dipped into water-ethanol solution of β-hydroxyl ethyl ester methacrylic acid (HEMA). After HEMA grafting with PU on the surface, PU-g-PHEMA (i.e. the grafted copolymer of HEMA onto PU) film was dipped into antistatic agent (TN). The PU-g-PHEMA-g-TN (i.e. the grafted copolymer of TN onto PU-g-PHEMA) film that has durable antistatic property on its surface was synthesized by PU-g-PHEMA film grafted with TN under catalysis of MgCl₂. The grafted copolymers were characterized by ATR-FTIR spectroscopy, Electron Spectroscopy for Chemical Analysis (ESCA), and Scanning Electron Microscopy (SEM), etc. The electrical property, thermal property, and mechanical behavior of PU after antistatic modification were tested. The results showed that after antistatic modification the surface electric resistivity of PU elastomer reached nearly 10⁸ Ω class, with little change in a washing-fastness experiment, while its mechanical ability and thermal characteristic were slightly decreased. The result of WAXD indicated that the regular construction degree of the grafted PU declined, the grafting chains distributed randomly on the surface of PU.     

Experimental investigation of charge carrier transport in organic thin-film transistors with "buried surface layers"

We studied how the layers with different transport properties buried inside a semiconductor material affect the characteristics of organic thin film transistors (OTFT) using a well-defined multilayered structure fabricated by a contact film transfer method that we recently developed (ACS Appl. Mater. Interfaces 1, 2660 (2009)). A simple model with the charge distribution in the organic semiconductor film, the mobility dependence on the charge density, and the buried surface layers with a high mobility successfully reproduced the experimental mobility dependence on the thickness of the spin-coated films and the gate voltage. These results demonstrated that charge transport layers located far from the dielectric interface could contribute significantly to the total current in OTFTs.     

Thermal and mechanical properties of HDPE/ionomer blends

The thermal behavior, tensile and tear strength of blends containing high density polyethylene (HDPE) and a sodium neutralized ethylene-methacrylic acid copolymer ionomer have been studied. It was found that each HDPE/ionomer blend had two well-separated melting peaks and two crystallization peaks, which indicates that the components of such a blend are immiscible with each other. The tensile behavior of the ionomer showed severe strainhardening just above the yield point, which leads to a lower elongation at break and a higher tensile strength than HDPE, possibly due to a network-like structure formation of ionic aggregates. The tensile properties of HDPE/ionomer blends were generally inferior to those of the pure components. Furthermore, the tensile properties exhibited severe negative deviation from linear additivity of properties, which is characteristic of incompatible blends. The negative deviation was also observed for tear strength of HDPE/ionomer blends. Observation of tear fracture surfaces of the blends showed fibrillar structure when ionomer content was relatively low. However, for the blends of higher ionomer composition much less fibrillation on the fracture surface was observed, which yields a higher value of tear energy. This is attributed to a network-like structure of the ionomer continuous phase of the blends.     

聚酰亚胺/二氧化钛纳米复合薄膜制备与耐电晕性

采用原位聚合法制备不同TiO₂组分聚酰亚胺(PI)/纳米TiO₂复合薄膜, 薄膜厚度50μm。 测试结果表明, TiO₂呈球状颗粒, 直径约为100 nm, 聚酰亚胺呈片状, 尺寸约为2μm×1μm。随着TiO₂含量的增加, 复合薄膜介电常数和介电损耗增大, 击穿场强先增加后降低; 在40 kV/mm电场强度下, 复合薄膜耐电晕老化寿命增加, 纯PI薄膜寿命为3 h, 20wt%TiO₂含量薄膜寿命达到25 h; TiO₂颗粒耐电晕能力强, 与聚合物形成界面相, 改变材料陷阱能级, 有利于空间电荷的扩散和热量的传输, 在薄膜表面形成放电阻挡层, 降低局部放电对薄膜内部的侵蚀, 显著提高薄膜耐电晕老化寿命。     

Growth and characterization of high resistivity c-axis oriented ZnO films on different substrates by RF magnetron sputtering for MEMS applications

In the present work, we report the deposition of high resistivity c-axis oriented ZnO films by RF magnetron sputtering. The deposition parameters such as RF power, target-to-substrate spacing, substrate temperature, and sputtering gas composition affect the crystallographic properties of ZnO films, which were evaluated using XRD analysis. The self-heating of the substrate in plasma during film deposition was investigated and we report that highly “c-axis oriented” ZnO thin films can be prepared on different substrates without any external heating under optimized deposition parameters. The post-deposition annealing of the film at 900 °C for 1 h in air ambient increases the intensity of (002) peak corresponding to c-axis orientation in addition with the decrease in full width at half maxima (FWHM). Bond formation of ZnO was confirmed by FTIR analysis. Grains distribution and surface roughness have been analyzed using SEM and AFM. The DC resistivity of the films prepared under different deposition conditions was measured using MIS/MIM structures and was found to be in the range of 10¹¹–10¹² Ω cm at low electric field of 10⁴ V/cm. The ZnO film of 1 μm thickness has transmittance of over 85% in the visible region. Applications of these films in MEMS devices are discussed.     

Formation of relatively pure alumina films by anodic polarization

Barrier-type film formation on aluminium in aqueous sodium and potassium hydroxide electrolytes of pH 11 was monitored using transmission electron microscopy of ultramicrotomed sections of the film attached to the substrate. Film growth to relatively low voltages in sodium hydroxide at a constant current density of 50 A m⁻² and associated high current efficiency develops typical barrier-type films of relatively pure alumina, as assessed by Rutherford backscattering spectroscopy, unlike the case with other forming electrolytes in which characteristic anions are generally incorporated in the outer regions of the films. For film growth in potassium hydroxide at a constant current density of 300 A m⁻² to high voltages, which is associated with an overall relatively low current efficiency of formation, an irregular film morphology develops, reminiscent of the appearance of barrier-type films that have suffered dielectric breakdown. In the present situation, where films were formed to voltages less than the breakdown voltage, it is thought that local current concentration, assisted by local heating, contributes to the morphology revealed; “conducting channels” within the film section provide the means for such non-uniform film growth, but precise reasons for their development are not yet clear.     

Correlation between photorefractivity,photoconductivity, and dark conductivity in dye-doped,low molecular mass nematic liquid crystal cells

The photoconductivity and photorefractivity of dye-doped low molecular mass nematic liquid crystal homeotropic cells exhibit a threshold at an applied voltage of the order of 1 V (in our samples). At about the same voltage, the dark conductivity of the cells exhibits a change from a cubic current/voltage characteristic to a linear one. We explain these observations by postulating that the cell's conductivity is due to ionic charge carriers generated near the electrodes by some electrochemical processes activated by the injection of electrons and holes. Below the noted threshold, the dark current is limited by a residual ionic space–charge distribution, and grows as the cube of the applied voltage. In this regime, photogenerated charge carriers are screened and are prevented from forming the static space–charge field needed to initiate an orientational photorefractive response. Above that threshold, the residual ionic space–charge disappears, the cell is a weak ohmic electrolyte, and the photogenerated charges contribute to the photoconductivity and photorefractivity of the cell.     

Charge-carrier injection into pentacene thin film formed on Si(111) probed by STM spectroscopy

The injection of charge carriers into a pentacene thin film formed on a Si substrate was investigated by scanning tunneling microscopy (STM). Tip height versus bias voltage (z-V) spectroscopy reveals the characteristic charge transport properties of the molecular film, i.e., the conductivity and the threshold energy of charge injection. The abrupt descent of the tip into the film owing to the transition of film conductance, which depends on the degree of charge carrier injection, was observed for crystallized pentacene thin films. The lower film conductance at around zero bias voltage is still higher than that of a vacuum. This indicates that the carrier injection barrier between the pentacene and the semiconducting substrate is extremely low. The convergence of the carrier injection endpoints into a narrow range of electric-field intensity implies that the main factor contributing to barrier formation and collapse is not the bias voltage but the electric field.     

Electrical properties of ITO/benzylated cyclodextrins (β-CDs (Bz))/Al diode structures

Abstract

Investigations of the electrical characteristics of benzylated cyclodextrins (β-CDs (Bz)) diodes are reported. We present current–voltage characteristics and impedance spectroscopy measurements performed on partially benzylated cyclodextrins β-CDs (Bz) thin films in sandwich structures ITO/b-CDs (Bz)/Al. The static electrical characterizations show a space charge limited conduction (SCLC) and a conductivity with power low frequency behavior characteristic of a hopping transport in disordered materials. The impedance spectra can be discussed in terms of an equivalent circuit model designed as a parallel resistor R_p and capacitor C_p network in series with resistor R_s. We extract numerical values of these parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution. We estimated from the capacitance voltage characteristic an acceptor concentration of about 10¹¹ cm^?3 due to trap states.