Variations in surface and electrical properties of polytetrafluoroethylene film after plasma-induced grafting of acrylic acid

Polytetrafluoroethylene(PTFE) film was graftpolymerized with acrylic acid(AAc) via a low-temperature plasma technique.The effect of plasma treatment parameters(radio-frequency power and treatment time) on the spin number of free radicals in PTFE film was examined.Attenuated total reflection Fourier transform infrared(ATR-FTIR)spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscopy,and atomic force microscopy were employed to characterize the chemical structure,surface composition,and microstructure of the original PTFE and PTFE-g-PAAc films,respectively,in order to verify the successful graft polymerization of AAc onto a PTFE film surface.Thermogravimetric analysis illustrated that the thermal stability of bulk PTFE film remains unchanged after graft modification.Water contact angle measurements confirmed that the hydrophilicity of PTFE-g-PAAc film was effectively improved as compared to the original PTFE film.The dielectric constant(ε_r) of PTFE-g-PAAc(GD =218 μg/cm~2) film remained invariable,compared to that of the unmodified PTFE film.Nevertheless,the dielectric loss(tanδ) of PTFE film increased considerably,from 0.0002(GD = 0μg/cm~2) to 0.0073(GD = 218 μg/cm~2),which might be due to the increase in surface polarity and moisture resulting from AAc graft modification.In addition,the surface electrical resistance(R_s) of PTFE film decreased slightly,from 131.89(GD = 0 μg/cm~2) to 110.28 Ω cm~2(GD = 218μg/cm~2) after surface modification,but still retained its inherent high impedance.     

Morphological changes in nanoparticulate silver films due to electron beam irradiation of polystyrene substrates

Results of the studies on the effect of 8 MeV electron beam irradiation of polystyrene substrates on the morphology of silver particulate films deposited at 455 K in a vacuum of 8 × 10⁻⁶ Torr are reported. Optical absorption studies show the presence of transverse and longitudinal plasmon resonance for films deposited on irradiated polystyrene. Scanning electron microscopy reveals a decrease in particle size with smaller inter-particle separation for irradiated films. Larger clusters are formed in the case of films deposited on polystyrene after 300 h of irradiation. In this paper, we show that the morphology of silver nanoparticulate films can be modified by electron irradiation of inert polymer substrates like polystyrene. The change observed due to irradiation is attributed to the formation of free radicals, thereby altering the polymer-metal interaction.     

Ar离子辐照PET膜引起的表面结构和组分变化研究

用35MeV/u的Ar离子室温下辐照多层堆叠的半晶质的聚酯（PET）膜,采用X射线衍射技术和X射线光电子谱仪分析研究了辐照引起的表面结构和组分的变化。结果表明：Ar离子辐照PET膜引起了明显的非晶化转变和化学键断裂、断裂主要发生在甲氧基和羰基功能团上,并使这两个功能团中的C和O的比分相对减少。非晶化效应和化学键断裂同时依赖于离子的照射剂量和离子在样品表面的电子能量损失、剂量越高,表面电子能量损失越大,效应就明显。同时定性地讨论了结果。     

聚合物表面辐射接枝改性研究进展

辐射接枝是聚合物表面改性的重要方法之一。本工作讨论了接枝单体和基材的性质、溶剂、酸、阻聚剂以及其它添加剂对聚合物辐射接枝反应的影响,介绍了利用光学显微镜、扫描电子显微镜原子力显微镜、凝胶色谱、X射线光电子能谱、拉曼光谱、红外光谱等所取得的接枝条件对接枝层的形态结构及接枝链长短研究结果。对近年来出现的能精确控制接枝链分子量和结构的活性聚合方法也作了简单介绍。     

Comparison of double layer in argon helicon plasma and magnetized DC discharge plasma

We present in this paper the comparison of an electric double layer (DL) in argon helicon plasma and magnetized direct current (DC) discharge plasma. DL in high-density argon helicon plasma of 13.56 MHz RF discharge was investigated experimentally by a floating electrostatic probe and local optical emission spectroscopy (LOES). The DL characteristics at different operating parameters, including RF power (300–1500 W), tube diameter (8–60 mm), and external magnetic field (0–300 G), were measured. For comparison, DL in magnetized plasma channel of a DC discharge under different conditions was also measured experimentally. The results show that in both cases, DL appears in a divergent magnetic field where the magnetic field gradient is the largest and when the plasma density is sufficiently high. DL strength (or potential drop of DL) increases with the magnetic field in two different structures. It is suggested that the electric DL should be a common phenomenon in dense plasma under a gradient external magnetic field. DL in magnetized plasmas can be controlled properly by magnetic field structure and discharge mode (hence the plasma density).     

195keV Ar^＋辐照非晶态合金表面损伤形貌的研究

用扫描电子显微镜观测研究了室温下１９５ｋｅＶＡｒ＋辐照非晶态合金Ｃｏ（６０）Ｆｅ（１２）Ｎｉ（１０）Ｓｉ６Ｂ（１２）和Ｆｅ（３９）Ｎｉ（３９）Ｖ２Ｓｉ（１２）Ｂ８在各剂量阶段的表面损伤形貌。结果表明，表面损伤是发泡和溅射相互竞争的过程。低剂量下，表面损伤以发泡为主；而在高剂量时，表面发泡消失，溅射造成的多孔粗糙表面损伤结构形成。对高剂量时表面发泡消失的可能机制作了探讨。     

Monte Carlo study of molecular weight distribution changes induced by degradation of ion beam irradiated polymers

In this work we study a polymeric material that degrades upon irradiation due to the energy inhomogeneously deposited by heavy ion beams. Ion beam irradiation of polymers generates rather different effects than those induced by “classical” low ionizing particles such as electrons or gamma rays. This is due to the high electronic stopping power and the inhomogeneous distribution of deposited energy. This energy is transferred to the material within a small volume along the ion path forming the so called “nuclear track” or “latent track”. The track size primarily depends on the ion velocity, and it is determined by the secondary electrons (delta rays) generated along the ion trajectory. By means of Monte Carlo simulations we first obtained equilibrated polymer configurations using a coarse-grained model, and then investigated the spatially inhomogeneous chain scission process due to the passage of the ions. The number average molecular weight, weight average molecular weight and the polydispersity were calculated as a function of track radius, scission probability within the ion track and irradiation fluence. Finally we compared our results with a numerical implementation of a model for random homogeneous degradation.     

Influence of air addition on surface modification of polyethylene terephthalate treated by an atmospheric pressure argon plasma brush

An atmospheric pressure argon plasma brush with air addition is employed to treat polyethylene terephthalate(PET) surface in order to improve its hydrophilicity. Results indicate that the plasma plume generated by the plasma brush presents periodically pulsed current despite a direct current voltage is applied. Voltage-current curve reveals that there is a transition from a Townsend discharge regime to a glow one during one discharge period. Optical emission spectrum indicates that more oxygen atoms are produced in the plume with increasing air content, which leads to the better hydrophilicity of PET surface after plasma treatment. Besides,an aging behavior is also observed. The hydrophilicity improvement is attributed to the production of oxygen functional groups, which increase in number with increasing air content.Moreover, some grain-like structures are observed on the treated PET surface, and its mean roughness increases with increasing air content. These results are of great importance for the hydrophilicity improvement of PET surface with a large scale.     

A low power 50 Hz argon plasma for surface modification of polytetrafluoroethylene

The characteristics of a low power 50 Hz argon plasma for surface treatment of polytetrafluoroethylene (PTFE) film is presented in this article. The current–voltage behavior of the discharge and time-varying intensity of the discharge showed that a DC glow discharge was generated in reversed polarity at every half-cycle. At discharge power between 0.5 and 1 W, the measured electron temperature and density were 2–3 eV and ∼10⁸ cm⁻³, respectively. The optical emission spectrum of the argon plasma showed presence of some 'impurity species' such as OH, N₂ and H, which presumably originated from the residual air in the discharge chamber. On exposure of PTFE films to the argon glow plasma at pressure 120 Pa and discharge power 0.5 to 1 W, the water contact angle reduced by 4% to 20% from the original 114° at pristine condition, which confirms improvement of its surface wettability. The increase in wettability was attributed to incorporation of oxygen-containing functional groups on the treated surface and concomitant reduction in fluorine as revealed by the XPS analysis and increase in surface roughness analyzed from the atomic force micrographs. Ageing upon storage in ambient air showed retention of the induced increase in surface wettability.     

Investigation of working pressure on the surface roughness controlling technology of glow discharge polymer films based on the diagnosed plasma

The effects of working pressure on the component, surface morphology, surface roughness, and deposition rate of glow discharge polymer(GDP) films by a trans-2-butene/hydrogen gas mixture were investigated based on plasma characteristics diagnosis. The composition and ion energy distributions of a multi-carbon(C_4H_8/H_2) plasma mixture at different working pressures were diagnosed by an energy-resolved mass spectrometer(MS) during the GDP film deposition process. The Fourier transform infrared spectroscopy(FT–IR), field emission scanning electron microscope(SEM) and white-light interferometer(WLI) results were obtained to investigate the structure, morphology and roughness characterization of the deposited films, respectively. It was found that the degree of ionization of the C_4H_8/H_2 plasma reduces with an increase in the working pressure. At a low working pressure, the C–H fragments exhibited small-mass and high ion energy in plasma. In this case, the film had a low CH_3/CH_2 ratio, and displayed a smooth surface without any holes, cracks or asperities. While the working pressure increased to 15 Pa,the largest number of large-mass fragments led to the deposition rate reaching a maximum of 2.11 μm h~(-1), and to hole defects on the film surface. However, continuing to increase the working pressure, the film surface became smooth again, and the interface between clusters became inconspicuous without etching pits.     

Improving the surface insulation of epoxy resin by plasma etching

Epoxy resin (EP) tends to accumulate a large amount of charge on its surface when exposed to a high-voltage DC electric field,which leads to a reduction in its insulative performance and an increase in potential safety risks in power systems.To suppress charge accumulation,improve the flashover voltage of the EP,and reduce the risk of gas insulated switchgear (GIS)/gas insulated transmission line (GIL) failure,we used two plasma-etching methods,i.e.,atmospheric-pressure dielectric barrier discharge (DBD) and the atmospheric-pressure plasma jet(APPJ),to modify the surface of the EP.The surface morphology and electrical properties of the modified materials were explored as a function of time.The results show that after DBD treatment,the roughness of the sample increases by 103.9 nm,the conductivity increases by3.9?×?10~(–18)S,and the flashover voltage increases by 14.4%;after APPJ treatment,the roughness of the sample increases by 223.5 nm,the conductivity increases by 3.4?×?10~(–17)S,and the flashover voltage increases by 18%.This shows that both plasma-etching methods can improve the insulation properties of materials by improving the surface-charge characteristics.The two methods are compared with each other:the APPJ treatment method is better at improving the surface roughness and electrical properties of materials,and this flexible treatment method has greater potential in industrial applications.     

Influence of the surface conditions on permeation in the deuterium–MANET system

The condition of the surfaces is of crucial importance for the deuterium permeation through materials. In this work a study of the surface constants for the adsorption (σk₁) and release (σk₂) of deuterium under different surface conditions on the martensitic steel DIN 1.4914 (MANET) has been carried out. The growth of an oxide surface layer (Cr₂O₃) of about 25–30 nm in a MANET sample, heat treated in an oxidizing environment, compared to the bare MANET that have a ‘natural' oxide of about 5 nm has provoked a reduction of both the permeation rate and the recombination coefficient (about 3 orders of magnitude). In addition, the permeation governing process has changed from diffusion-limited to surface-limited. The measurements of the permeation rate of deuterium were performed by a gas-phase permeation technique over the temperature range 574–746 K and for deuterium driving pressures in the range from 3 to 10⁵ Pa.     

用于材料表面强化处理的第三代多功能PⅢ装置

第三代多功能等离子体浸没离子注入（PⅢ）装置的强流脉冲阴极弧金属等离子体源既具有强的镀膜功能，同时也具有强的金属离子注入功能；它的脉冲高压电源能输出大的电流；并可获得高的注入剂量均匀性。该装置既能执行离子注入，又能把离子注入与溅射沉积，镀膜结合在一起，形成多种综合笥表面改性工艺。本文描述了它的主要设计原则、主要部件的特性以及近期的研究工作成果。