Polypropylene Films in a Direct-Current Discharge

The effect of dc discharge treatment on polypropylene films—both commercial and stabilizer- and plasticizer-free as prepared under laboratory conditions (with the rac-Et(Ind)₂ZrCl₂–methylaluminoxane catalytic system)—was studied. The discharge treatment was shown to hydrophilize the polypropylene surface in both cases. Negative charged states were detected on the modified surface and their relation to the polypropylene hydrophilization was established. By the thermostimulated relaxation and depolarization techniques, it was shown that the observed charges are induced by injection of plasma electrons into the polymer. It was found that severe changes took place throughout the bulk of the polypropylene film synthesized over the metallocene catalyst, as indicated by enhancement of its crystallinity and a change in the molecular mass distribution.     

Adhesion Properties of Films of Polypyromellitimide Modified in a Direct-Current Discharge

Adhesion properties of films of polypyromellitimide modified in a direct-current discharge on the anode are investigated. The peeling strength in when in contact with a series of polymers and with the use of adhesives of different chemical natures is measured using the T-peel test according to ASTM 1876–01. It is shown that the action of a direct current discharge on the films of polypyromellitimide makes it possible to substantially improve the adhesion properties of the polymer to adhesives of different types.     

Polymerization of 3-Methoxythiophene in a Direct-Current Discharge

Thin polymer films were obtained from 3-methoxythiophene at the cathode in a dc discharge. It was found using Fourier transform IR spectroscopy that thiophene rings were the main structural units of the polymer; aliphatic fragments and oxygen-containing groups were also present. The polymer based on 3-methoxythiophene was found to exhibit p-type intrinsic conduction with an activation energy of 0.045 eV. The conductivity of the polymer at 20°C was 10⁻⁸ Ω⁻¹ cm⁻¹, and doping with iodine resulted in a rise in conductivity to 10⁻³ Ω⁻¹ cm⁻¹.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 5, 2005, pp. 382–385.Original Russian Text Copyright © 2005 by Drachev, Gil’man, Krasovskii, Costa-Belobrzeckaja.     

Contact Properties and Surface Structure of Polypyromellitimide Films Modified by Direct-Current Discharge

High Energy Chemistry - The contact properties, chemical structure, and surface morphology of polypyromellitimide films modified at the cathode and anode by dc discharge have been investigated. A...     

Modification of Polyvinyltrimethylsilane in Direct-Current Discharge

High Energy Chemistry - The modification of polyvinyltrimethylsilane under treatment by direct-current discharge at a reduced pressure has been investigated. Polymer films were placed at the anode...     

Evaluation of the Distribution Depth of Charge Injected by Direct-Current Discharge Plasma into Thin Polyimide and Poly(ethylene terephthalate) Films

The dynamic capacitor method was proposed for determining the distribution depth of negative charge induced in the surface layers of thin polymer films under exposure to a dc discharge as a result of trapping plasma-injected electrons, and equations for calculation were obtained. Charge distribution in thin poly(pyromellitimide) and poly(ethylene terephthalate) films with different thickness (1–6 m) was experimentally studied, and the negative charge due to the injection of electrons from plasma was found penetrate to a depth greater than 0.5 m.     

Conducting Polymer Layers Obtained by Direct-Current Discharge Polymerization of 1-Amino-9,10-anthraquinone

The polymerization of 1-amino-9,10-anthraquinone in a direct-current discharge was studied. It was found that polymer films with a conductivity of 10^–5–10^{–4 –1} cm^–1 were formed at the cathode. It was assumed that the semiconductor properties are due to the presence of a conjugated cyclic moiety in the films. The layers deposited at the anode turned out to be typical dielectrics with a conductivity of 10^{–16 –1} cm^–1.     

聚乙撑二氧噻吩膜在氧化态的充电过程及电容研究

In this paper, the chronoamperometry was used to study the charging processes of polyethylenedioxythiophene (PEDOT) modified electrodes in the potential range where PEDOT was in the oxidized state. The results show that the charging behaviors of the PEDOT films are well agreed with the exhausted finite diffusion model. The dependence of the capacitance values of the films on potential and concentration of solution was also studied in this potential range.     

Optical Properties of Swift Heavy Ion Beam Irradiated Polycarbonate/Polystyrene Composites Films

Polycarbonate/polystyrene composites films were irradiated by 55 MeV Carbon ion beam with fluence ranging from 1 × 10¹¹ to 1 × 10¹³ ions/cm². The polymer composites films were prepared by solution mixing method. The effects of ion beam on structural, optical and surface morphology of PC/PS composites films were investigated by X-ray diffraction (XRD), UV-visible spectroscopy (UV-vis), Fourier Transform Infrared Spectroscopy (FT-IR) and Optical Microscope. The XRD pattern shows the average crystallite size, percentage of crystallinity and inter-chain separation, which decreases with increase in ion fluences. UV-vis spectra show that the energy band gap and transmittance decreases while number of carbon atoms increases with fluences. The FT-IR spectra evidenced very small change in cross linking and chain scissoring at high ion fluences, while the optical microscopy shows a color change with ion fluence.     

Deposition of Silver Nanostructures on Polymer Films by Glow Discharge

Plasma Chemistry and Plasma Processing - An atmospheric pressure glow discharge generated between the solid cathode and liquid anode was applied to produce silver nanoparticles and deposition of...     

Characterization of Plasma Polymerized Hexamethyldisiloxane Films Prepared by Arc Discharge

Herein, we present a simple method for fabricating plasma polymerized hexamethyldisiloxane films (pp-HMDSO) possessing superhydrophobic characteristics via arc discharge. The pp-HMDSO films were deposited on a soda–lime–silica float glass using HMDSO monomer vapor as a precursor. A detailed surface characterization was performed using scanning electron microscopy and atomic force microscopy. The growth process of the pp-HMDSO films was investigated as a function of deposition time from 30 to 300 s. The non-wetting characteristics of the pp-HMDSO films were evaluated by means of contact angle (CA) measurements and correlated with the morphological characteristics, as obtained from microscopy measurements. The deposited films were found to be nano-structured and exhibited dual-scale roughness with the static CA values close to 170°. Fourier transform infrared spectroscopy analysis was carried out to investigate chemical and functional properties of these films. Methyl groups were identified spectroscopically to be present within the pp-HMDSO films and were proposed to result in the low surface energy of material. The synergy between the dual-scale roughness and low surface energy resulted in the superhydrophobic characteristics of the pp-HMDSO films. A possible mechanism for the pp-HMDSO film formation is proposed.     

Low-Frequency Glow Discharge Treatment of Poly(ethylene terephthalate) Films

The alteration of surface characteristics of the PET-E poly(ethylene terephthalate) film by treatment in the cathode fall of an ac (50 Hz) glow-discharge plasma was studied. The plasma-assisted modification leads to surface hydrophilization which is retained for a long period of time. It was found that the discharge treatment induced a negative charge in the polymer surface layer. The charge density created under different treatment conditions was correlated with the contact angle. The thermally stimulated relaxation and depolarization measurements on the original and the modified film showed that charge buildup in the film during the discharge treatment was due to trapping of injected electrons. From the experimental data, it was inferred that the charge states emerged play the determining role in enhancing the surface energy of modified PET films.     

Contact Properties of Polytetrafluoroethylene Films Modified in Nonthermal Plasma of Atmospheric-Pressure Argon Glow Discharge

High Energy Chemistry - It has been shown that plasma treatment of the surface of a polytetrafluoroethylene film in nonthermal plasma of atmospheric-pressure glow discharge makes it possible to...     

Two-Dimensional Numerical Modeling of Direct-Current Electric Arcs in Nonequilibrium

A numerical model has been developed to analyze arc-anode attachment in direct-current electric arcs. The developed model fully couples a plasma flow with electromagnetic fields in a self-consistent manner. Electrons and heavy species are assumed to have different temperatures. Species continuities are taken into account to address the chemical nonequilibrium with the Self-Consistent Effective Binary Diffusion (SCEBD) formulation. Electric and magnetic field equations are determined with a newly developed Ohm’s law, an improvement over the conventional generalized Ohm’s law. The governing equations are discretized and solved using the Finite Volume Method (FVM) and Gauss–Seidel Line Relaxation (GSLR) method in a two-dimensional domain. The model is applied to a two-dimensional axisymmetric high-intensity argon arc. The results are compared favorably with experimental and other numerical data. A significant electric potential drop has been observed in the vicinity of the anode due to the thermal and chemical nonequilibrium effects.     

Charging effects in a CdSe nanotetrapod

The charging effects in a CdSe nanotetrapod have been theoretically investigated by using an atomistic pseudopotential method. We showed that the simple quasiparticle equation based on classical electrostatic consideration can be derived from the many-body GW equation under proper approximations. We found that the surface polarization potential can significantly change the electron wave functions, and there is an incomplete cancellation for this potential between the single particle energies and the electron-hole Coulomb interaction. Thus, it is necessary to include this potential in the calculation for complex unconvex systems. We also calculated the electron addition energies for a tetrapod. Unlike a simple spherical quantum dot, in which the addition energies are almost a constant, there is a large variation in the calculated addition energies for different numbers of electrons in a tetrapod.     

脂肪族聚碳酸酯共聚物的研究进展

脂肪族聚碳酸酯共聚物是一类可完全生物降解的新型材料,自1969年井上祥平等首次通过二氧化碳与环氧化合物反应合成脂肪族聚碳酸酯以来,人们在将二氧化碳固定为全降解聚合物这一研究领域取得了大量研究成果.本文综述了用于二氧化碳和环氧化合物共聚合成脂肪族聚碳酸酯的各类催化剂及反应机理,讨论了脂肪族聚碳酸酯结构/性能关系,并简要介绍了其在不同领域的应用.     

The Breakdown Phenomena in Micrometer Scale Direct-Current Gas Discharges

This paper reports on experimental and theoretical studies of the direct current breakdown voltage characteristics for several gases (argon, nitrogen, helium, hydrogen, dry air, oxygen and carbon dioxide) in discharges with parallel-plane electrodes separated from 1 to 100 μm. The breakdown phenomena have been discussed in terms of field emission of electrons from the cathode. Based on the measured breakdown voltage curves, realistic values of the effective yields and the field emission thresholds for considered gases have been estimated. It was found that the secondary electron emission due to high electric field generated in microgaps depends primarily on the electric field E leading directly to the violation of the Paschen’s law. The effective yields due to the field emission for all gases are determined for the first time. Experimental data are supported by the theoretical predicitions that suggest departure from the scaling law and a flattening of the Paschen curves at higher pressures. The obtained results may provide better understending of the breakdown phenomena in microgaps.     

Decoupling Study of Melt Polycondensation of Polycarbonate: Experimental and Modeling of Reaction Kinetics and Mass Transfer in Thin Films Polycondensation Process

During the melt polycondensation process of polycarbonate, reaction and mass transfer are deeply coupled owing to relatively high melt viscosity. In this work, the polycondensation reaction kinetics and mass transfer behavior of volatile phenol are decoupling studied in detail by using thin‐film experiments with 250–280 °C, 10–1000 Pa and 0.085–0.68 mm film thickness. A realistic apparent rate model coupled the reaction kinetics with thermodynamic equilibrium and diffusion behavior is developed to describe the polycondensation process, while the diffusion characteristic of small molecule (phenol) is further obtained based on penetration theory. The obtained polycondensation equilibrium constant ranges from 0.3 to 0.55, while the activation energy and pre‐exponential factor of temperature‐dependent diffusion coefficients of phenol are 87.9 kJ mol⁻¹ and 5.08 × 10² m² s⁻¹, respectively. It is also observed that the overall apparent rate of polycarbonate (PC) polycondensation process increases with higher temperature, lower pressure, and thinner film thickness. Coupling the reaction kinetics with mass transfer, the predictions of the realistic apparent rate model are in quite satisfactory agreement with experimental data.     

Deposition of Polyacrylic Acid Films by Means of an Atmospheric Pressure Dielectric Barrier Discharge

The present work describes the plasma polymerisation of acrylic acid at atmospheric pressure. The influence of two operating parameters (monomer concentration and discharge power) on the properties of the deposited films is investigated. Results show that at a monomer concentration of 2.5 ppm and a discharge power of 9.5 W, the monomer is only slightly fragmented leading to a high amount of carboxylic acid groups on the deposited films. In contrast, when monomer concentration is decreased or discharge power increased, the incidence of monomer fragmentation processes is higher, leading to a lower amount of carboxylic acid groups on the films. This behaviour can be explained by a higher energy amount available per monomer molecule at low monomer concentrations and high discharge powers and a higher flux of positive ions attacking the surface at high discharge powers. Taking into account these results, it can be concluded that the deposition parameters should be carefully selected in order to preserve the stability of the monomer and thus obtain coatings with high carboxylic acid densities.