纳秒脉冲放电对聚对苯二甲酸乙二酯憎水改性

基于自主研制的ns脉冲电源(上升沿约70ns,脉宽约100ns)激励介质阻挡放电产生大气压低温等离子体,在CF4气氛下对聚对苯二甲酸乙二酯(PET)表面进行了憎水改性处理,测量了改性前后的薄膜表面的水接触角,给出了CF4气流量、放电电压、处理时间和CF4比例等参数对改性效果的影响规律。结果表明,大气压ns脉冲DBD表面处理能够实现PET材料的憎水性,改性后的PET表面水接触角由66°提高到最大100°。     

交流和纳秒脉冲Ar/H2O介质阻挡放电聚丙烯材料表面亲水改性对比研究

为了提高等离子体对聚合物材料表面处理的应用效果,优化亲水处理的条件,研究了交流和纳秒脉冲氩气介质阻挡放电（DBD）中添加适量H₂O,对聚丙烯（PP）亲水改性的处理效果。利用电学和光学诊断方法,系统地对比了交流DBD和纳秒脉冲DBD的放电特性,结果表明,纳秒电源驱动DBD具有更高的放电瞬时功率,更好的放电均匀性和更高的能量效率。通过测量不同水蒸气含量下DBD的OH发射光谱强度,确定了PP材料亲水性处理中H₂O添加的最优含量。利用交流和纳秒脉冲电源驱动DBD分别对PP材料进行亲水改性的处理,测量了不同条件下改性处理后的表面水接触角,并利用原子力显微镜（AFM）和傅里叶红外光谱（FTIR）分别对处理前后PP材料的表面物理形貌和表面化学成分进行分析。结果发现,经DBD处理后PP材料的水接触角明显降低,表面粗糙度明显增大,表面的亲水性含氧基团,羟基（?OH）和羰基（C=O）的数量大幅增加。相比交流电源,纳秒脉冲DBD处理的改性效果更好,其处理后的材料表面水接触角,比交流DBD处理的低5°左右,表面粗糙度也有所提升。而水蒸气的加入可使PP材料的表面水接触角进一步减小4°左右,表面粗糙度明显提升。研究结果为优化DBD聚合物材料表面改性实验条件及处理的效果提供了重要的参考依据。     

Statistical analysis of the effect of dielectric barrier discharge (DBD) operating parameters on the surface processing of poly(methylmethacrylate) film

A dielectric barrier discharge (DBD) plasma, operating in air at atmospheric pressure, has been used to induce changes in the surface properties of poly(methylmethacrylate) (PMMA) films. The relative effects that key DBD operating parameters, specifically: discharge power, electrode gap and duration of exposure have on producing chemical and microstructural changes in the polymer surface region have been investigated. The approach taken involves the application of an orthogonal array experimental design and statistical analysis methodology. The various data sets obtained from these analyses have been used to develop an equation in which induced changes in the surface properties of the DBD modified PMMA films are expressed in terms of the effectiveness of the various processing parameters in producing them.In general, the results obtained clearly indicate that DBD plasma processing is an effective method for the controlled surface modification of PMMA. Relatively short exposures to the atmospheric pressure discharge produces a significant amount of oxygen incorporation at the surface as indicted by a pronounced reduction in water contact angle. Analysis of the role of each of the operating parameters concerned shows that they do indeed have selective effectiveness for inducing resultant surface modification. Duration of exposure to the DBD plasma, expressed here as the number of treatment cycles at a given speed of specimen transit through the electrode gap, was found to play a major role in decreasing the surface wettability of PMMA. Conversely, the magnitude of the discharge power was not a significant parameter in this regard. In contrast, the value of the applied power played the dominant role in achieving the observed enrichment of the surface oxygen abundance, as measured by XPS, with the duration of exposure to the discharge playing a secondary role in this case.The nature and scale of the induced surface changes that originate from the various processing conditions employed have been further considered to determine if an interrelationship exists between them. Non-parametric data analysis indicates that no significant correlation exists between the observed changes in measured polymer wettability and the attendant surface oxygen enrichment. This result suggests that the increase in surface wettability caused by DBD processing, as manifested in a reduced contact angle, is not merely attributable to changes in the surface chemistry. As such, it is postulated that changes in the surface microstructure may also contribute to this change in surface wettability.     

Surface modification of polyimide films using unipolar nanosecond-pulse DBD in atmospheric air

DBD-induced surface modification is very versatile to increase the adhesion or hydrophilicity of polymer films. In this paper, the DBD is produced by repetitive unipolar nanosecond pulses with a rise time of 15 ns and a full width at half maximum of about 30 ns. The power densities of the homogeneous and filamentary DBDs during plasma treatment are 158 and 192 mW/m², respectively, which are significantly less than that using ac DBD processing, and the corresponding plasma dose is also mild compared to AC DBD treatment. Surface treatment of polyimide films using the homogeneous and filamentary DBDs is studied and compared. The change of chemical and physical modification of the surface before and after plasma processing has been evaluated. It can be found that both surface morphology and chemical composition are modified, and the modification includes the rise of hydrophilicity, surface oxidation and the enhancement of surface roughness. Furthermore, the homogeneous DBD is more effective for surface processing than the filamentary DBD, which can be attributed to the fact that the homogeneous DBD can modify the surface more uniformly and introduce more polar functional groups.     

Study on dielectric surface discharge in transformer oil under high voltage nanosecond pulse

Electrical equipments are always subjected to different operating conditions and voltage waves which cause electrical failure on the surface and in the bulk of dielectrics. In this paper, experiments have been carried out to study main factors that influence the characteristic of dielectric surface discharge in transformer oil. Experimental study on flashover of nylon 6 and polymethyl methacrylate (PMMA) under applied voltage ranged from 50 to 250 kV shows that the flashover voltage U is influenced by the insulation structure, rise velocity and pulse width of the applied voltage. Flashover electrical field value E in pulse with rise time less than 10 ns is higher than that in DC and AC voltages. When angle between electrode and the sample is about 45°, nylon 6 and PMMA show the best flashover performance. From these results, the influence of the secondary electron emission and space charges on the electrical breakdown of dielectrics has been stressed.     

Characterization of a non-thermal plasma torch in streamer mode and its effect on polyvinyl chloride and silicone rubber surfaces

In this study, a non-thermal plasma torch in steamer mode was characterized to apply for surface modification in ambient air. The plasma source is a central rod-ring configuration based on DBD operation. Mixture of Ar/air gases was passed through the hollow Copper rod. A home-built high voltage generator at 18.8 kHz was employed to ignite the plasma. Electrical features of plasma torch were studied and different regions of plasma were examined using optical emission spectroscopy to explore the reactive species that result in efficient treatment. The surfaces of polyvinyl chloride (PVC) and silicone rubber (SIR) films were treated by the cold plasma torch. Contact angle measurement shows the improvement of surface hydrophilicity and wettability. Analysis revealed that the surface energy of the films increases indicating their activation after plasma treatment. This process is attributed to increasing the polar component of the surface energy.     

等离子体介质阻挡放电氟化改性环氧树脂的时效性

等离子体对材料的改性效果随放置时间会有所减弱,即表现出一定的时效性,限制了等离子体改性技术的进一步发展。为了探究等离子体介质阻挡放电（DBD）氟化改性环氧树脂的时效性,利用等离子体介质阻挡放电实现了环氧树脂表面氟化改性,并利用扫描电镜（SEM）、表面轮廓仪、X射线光电子能谱分析（XPS）、接触角测试仪、高阻计和闪络电压、表面电位测试系统对改性前和改性后放置在25 ℃老化箱中0～30 d的环氧树脂表面进行了物理形貌和化学组分的表征以及电气性能的测试。测试结果表明,DBD氟化改性实现了氟元素在环氧树脂表面接枝,这使得环氧树脂表面能降低,表面电阻率减小,陷阱能级变浅,从而加快了表面电位衰减速度,进而提升了沿面闪络电压。同时,等离子体DBD氟化改性环氧树脂表现出一定的时效性,放置30 d后,氟元素含量减少,表面能增大,表面电位衰减速度略有减慢,闪络电压也有所下降,但仍高于未处理的试样。     

纳秒脉冲表面介质阻挡放电特性实验研究

在常规大气环境条件下,基于单极性纳秒脉冲电源对表面介质阻挡放电特性进行了实验研究。结果表明:纳秒脉冲表面介质阻挡放电的本质是丝状放电,放电集中在电压脉冲的上升沿;激励电压和脉冲重复频率越大,放电越强烈,越接近均匀放电,但电压的作用更侧重于均匀性,而频率的作用则侧重于放电的强度;电极间隙的优化可以使表面介质阻挡放电特性最好;玻璃作为阻挡介质时容易发生沿面闪络。     

重复频率纳秒脉冲介质阻挡放电对聚对苯二甲酸乙二酯表面改性

介绍了0.1 MPa下的纳秒脉冲介质阻挡放电(DBD)对聚对苯二甲酸乙二酯(PET)材料表面进行的亲水性改善。分别采用均匀和丝状放电模式对PET表面改性处理,并采用水接触角测量、原子力显微镜观察、X射线光电子能谱分析对改性材料进行表面分析。实验发现介质阻挡放电处理后PET表面水接触角明显减小,接触角从78°下降到25°,但随处理时间的增加有饱和效应;PET表面粗糙程度增加,亲水性含氧基团被引入,从而改善了材料表面亲水性;纳秒脉冲下的均匀DBD比丝状DBD处理效果更为显著。     

Functionalization of PET and PA6.6 woven fabrics

In the present work as received woven fabrics of polyethylene terephthalate (PET) and polyamide 6.6 (PA6.6) were exposed to a continuous dielectric barrier discharge (DBD), in air at atmospheric pressure, at selected discharge power values and conveyor speeds. The chemical modification of the fabric surface was studied by contact angle analysis, attenuated total reflection (ATR)-FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). The results confirmed that the treatment changed the fabric surface chemistry, increasing its wettability by polar liquids and its oxygen content. Contact angle results showed different behaviour of the two polymer fabrics toward ageing effects; while PET showed a contact angle increase along the subsequent days of treatment, the PA6.6 fabric maintained its hydrophilicity even 15 days after treatment. The surface morphology analysed by scanning electron microscopy (SEM), did not show any significant difference before and after treatment.     

Preparation of hydrophobic coating on glass surface by dielectric barrier discharge using a 16 kHz power supply

A 16 kHz power supply was used to investigate the preparation of hydrophobic film on glass surface by means of atmospheric pressure dielectric barrier discharge (DBD). Air nonthermal plasma was induced between the two parallel electrodes with a glass plate as dielectric barrier. The process for hydrophobic film includes two parts: one is plasma pretreatment to produce active layer on glass surface, another is to form hydrophobic film on glass surface by means of the interaction between air plasma and polydimethylsiloxane oil. The surface changes were observed using contact angle measurement and atomic force microscope. The results show DBD can increase surface roughness, and effectively improve glass surface activation and form a hydrophobic coating on glass surface, and it is possibility to prepare hydrophobic glass with middle frequency power supply.     

Geometrical optimization of a surface DBD powered by a nanosecond pulsed high voltage

In this study, surface Dielectric Barrier Discharge (DBD) actuators powered by nanosecond pulsed high voltage are investigated. The goal is to experimentally characterize the surface DBD actuators in terms of electrical and geometrical parameters.The actuators are made of two conducting electrodes separated by a thin dielectric (Kapton films) and arranged asymmetrically. The active electrode is connected to a pulsed high voltage power supply (voltage up to ±10 kV, rise and fall times of 50 ns and pulse width of 250 ns) and the second electrode is grounded.The experimental results show that the energy per pulse (normalized by the length of the active electrode) is smaller when one increases the inter-electrode spacing between 1 and 3 mm, the thickness of the dielectric barrier between 120 and 360 μm or the length of the electrodes between 10 and 50 cm, for both applied voltage polarities.Optical characterization of the plasma layer for different electrode gaps has been investigated by using an ICCD camera. Results indicate that the plasma produced by positive and negative rising voltage propagates in a streamer-like regime with numerous and well-distributed channels, for any electrode gap distance. However, the positive and negative falling voltage produces similar discharges only for large electrode gaps. In this case, the plasma layer starts from a corona spot in contact with the active electrode and expands in the direction of the grounded electrode in a plume shape.     

米量级常压等离子体改性装置及其在纺织材料改性中的应用

介绍了自制的1m尺度介质阻挡电连续表面改性处理装置。论述了米量级常压介质阻挡放电的物理特性,探讨了介质阻挡放电的电压、功率、频率等电学参量之间的关系。给出了使用此装置连续对涤纶(PET)织物、熔喷PBT非织造布和羊毛织物三种纺织材料进行改性实验结果,得到了相应的扫描电子显微镜(SEM)图片,分析了材料表面改性的原因。     

The effect of discharge power density on polyethylene terephthalate film surface modification by dielectric barrier discharge in atmospheric air

Polyethylene terephthalate (PET) films are modified using non-equilibrium plasma generated by DBD in atmospheric air, and the effects of discharge power density on the surface modification are studied. It is found that increasing discharge power density can induce more effective treatment of PET films, because this leads to a faster decrease in water contact angle and a faster increase in surface energy due to more creation of polar groups and more obvious etching occurring on the PET surface. So the treatment time needed to achieve the same level of surface treatment can be reduced by increasing the discharge power density.     

Surface oxidation of a Melinex 800 PET polymer material modified by an atmospheric dielectric barrier discharge studied using X-ray photoelectron spectroscopy and contact angle measurement

Surface properties of a Melinex 800 PET polymer material modified by an atmospheric-pressure air dielectric barrier discharge (DBD) have been studied using X-ray photoelectron microscopy (XPS) and contact angle measurement. The results show that the material surface treated by the DBD was modified significantly in chemical composition, with the highly oxidised carbon species increasing as the surface processing proceeds. The surface hydrophilicity was dramatically improved after the treatment, with the surface contact angle reduced from 81.8° for the as-supplied sample to lower than 50° after treatment. Post-treatment recovery effect is found after the treated samples were stored in air for a long period of time, with the ultimate contact angles, as measured, being stabilised in the range 58-69° after the storage, varying with the DBD-treatment power density. A great amount of the C-O type bonding formed during the DBD treatment was found to be converted into the CO type during post-treatment storage. A possible mechanism for this bond conversion has been suggested.     

Effect of atmospheric pressure dielectric barrier discharge air plasma on electrode surface

In order to study the influence of plasma on electrode, atmospheric pressure dielectric barrier discharge (DBD) air plasma is employed here to treat copper electrode surface. Plasma is generated between the parallel plate electrodes by means of high voltage produced by a high-frequency power supply with transformer. Electrode surface alterations induced by air plasma are investigated by using field emission scanning electron microscope (FE-SEM), X-ray energy dispersion spectroscopy (EDS) and contact angle measurement. The results show that DBD air plasma removes the organic contaminant on surface and causes electrode surface roughness, oxidization and nitridation. In addition, surface wettability is also improved, as concluded from contact angle measurements.     

Uniformity analysis of dielectric barrier discharge (DBD) processed polyethylene terephthalate (PET) surface

A dielectric barrier discharge (DBD) plasma, operating in air at atmospheric pressure, has been used to induce changes in the surface properties of polyethylene terephthalate (PET) films. The effects that the key DBD operating parameters: discharge power, processing speed, processing duration, and electrode configurations, have on producing wettability changes in the PET surface region have been investigated. The approach taken involves the application of an Taguchi experimental design and robust analysis methodology. The various data sets obtained from these analyses have been used to studies the effect of the operating parameters on the surface uniformity and efficiency of the said treatment.In general, the results obtained indicate that DBD plasma processing is an effective method for the controlled surface modification of PET. Relatively short exposures to the atmospheric pressure discharge produces significant wettability changes at the polymer film surface, as indicted by pronounced reductions in the water contact angle measured. It was observed that the wettability of the resultant surface shows no significant differences in respect to orientation parallel (L-direction) or perpendicular (T-direction) to the electrode long axis. However, there was significant differences between the data obtained from these two orientations. Analysis of the role of each of the operating parameters concerned shows that they have a selective effectiveness with respect to resultant surface modification in terms of uniformity of modification and wettability. The number of treatment cycles and the electrode configuration used were found to have the most significant effects on the homogeneity of the resultant PET surface changes in L- and T-orientation, respectively. On the other hand, the applied power showed no significant role in this regard. The number of treatment cycles was found to be the dominant factor (at significance level of 0.05) in respect of water contact angle changes at the processed PET surface in both orientations. The driven metal electrodes (stainless steel or aluminium) were apparently superior to the driven dielectric electrode (ceramic or quartz) configurations. The grounded electrode in each case was a silicon rubber-covered aluminium plate (see later). The nature and scale of the surface changes that originate from the various processing conditions employed have been considered so as to determine the optimum treatment conditions in respect of processing outcomes, properties and any orientation dependence. Thus, it was revealed that higher processing speeds and longer processing durations are key for uniformity along the electrode axial orientation, while lower processing speeds and short exposure durations are key considerations, in the corresponding perpendicular orientation. In general, longer processing durations (low processing speeds and a high number of treatment cycles) and higher plasma powers induced greater changes in the surface wettability of the PET, as demonstrated by the observed water contact angles. This behaviour is taken to indicate that different combinations of DBD operating parameters and electrodes produce discharge conditions that can result in different plasma chemical processes in respect of uniformity, treatment efficiency and orientation dependence.     

Hydro-oleophobic silica antireflective films with high laser-damage threshold

A simple method of preparing hydro-oleophobic anitreflective films with high laser-damage threshold is reported in this article. By adding fluoroalkylsilanes (FAS) into reactant mixture as a co-precursor, FAS modified SiO₂ was obtained under base catalyzed hydrolysis and condensation of tetraethoxysilane. The dip-coating films were deposited on two sides of fused silica substrates.The experimental results on the effect of adding fluoroalkylsilanes (FAS) as a co-precursor on the hydro-oleophobicity and optical properties of tetraethoxysilane (TEOS) based silica AR films, are reported. The hydro-oleophobicity of the films was tested by the contact angle measurements and the highest water contact angle of 136° and oil (peanut) contact angle of 93° were obtained. The surface chemical modification of the hydro-oleophobic films was confirmed using Fourier transform infrared spectroscopy (FTIR). For the films based on FAS and TEOS, additional absorption bands at 1100 cm^?1 corresponding to C–F bond presented, clearly indicating the organic modification of the films. The highest optical transmittance of the hydro-oleophobic films was found to be 99.5%. By a Nd:YAG lasers the laser-damage threshold of as-deposited films was measured at 351 nm wavelength (1 ns). The laser-damage threshold was as high as 22.6 J/cm².     

空气中纳秒脉冲介质阻挡放电高速摄影

使用上升沿40 ns、脉宽70 ns的重复频率单极性纳秒脉冲电源,采用双水电极结构产生大气压空气中介质阻挡放电。测量了纳秒脉冲下介质阻挡电压和电流,并获得长曝光时间和ns级曝光时间的放电特性,采用曝光时间为2 ns的高速摄影拍摄放电发展过程。结果表明:大气压空气中,水电极结构纳秒脉冲介质阻挡放电能够产生稳定均匀的放电等离子体,且存在二次放电。高速摄影对放电发展过程的拍摄结果表明:放电首先由电极中部开始发展,径向扩展至整个电极范围。     

Fluorination of polymethylmethaacrylate with tetrafluoroethane using DC glow discharge plasma

Fluorination of polymer surfaces has technological applications in various fields such as microelectronics, biomaterials, textile, packing, etc. In this study PMMA surfaces were fluorinated using DC glow discharge plasma. Tetrafluoroethane was used as the fluorinating agent. On the fluorinated PMMA surface, static water contact angle, surface energy, optical transmittance (UV-vis), XPS and AFM analyses were carried out. After the fluorination PMMA surface becomes hydrophobic with water contact angle of 107° without losing optical transparency. Surface energy of fluorine plasma-treated PMMA decreased from 35 mJ/cm² to 21.2 mJ/cm². RMS roughness of the fluorinated surface was 4.01 nm and XPS studies revealed the formation of C-CF_x and CF₃ groups on the PMMA surface.