Improvement of adhesion of fucoidan on polyethylene terephthalate surface using gas plasma treatments

Attachment of polysaccharide fucoidan to the polyethylene terephthalate (PET) polymer surface was studied by X-ray photoelectron spectroscopy (XPS). Fucoidan has antithrombogenic and anticoagulant properties and is therefore a promising coating for vascular graft implants for improving their hemocompatibility. Samples of PET polymer were first modified by nitrogen plasma treatment in order to change the surface wettability and to introduce amino groups to the surface, which act as a linker for further binding of fucoidan. Plasma treated samples were then incubated for 30 min in fucoidan solution. The presence of fucoidan layer on the polymer surface was demonstrated by appearance of S2p signal in the XPS spectra of the coated PET samples. The procedure for immobilization of fucoidan on PET surface was optimized by varying pH value of fucoidan solution from 5 to 7.4. The best results were obtained when using lower pH value pH = 5. At these conditions the thickness of the fucoidan coating was estimated to about 7 nm.     

Surface modification and ageing of PMMA polymer by oxygen plasma treatment

We present a study on ageing of polymethyl methacrylate (PMMA) polymer treated with oxygen plasma. Oxygen plasma was created with an RF generator operating at a frequency of 27.12 MHz and a power of 200 W. The oxygen pressure was 75 Pa. The samples were treated for different time from 5 s to 60 s. The chemical modifications of the surface after plasma treatment were monitored by XPS (X-ray photoelectron spectroscopy), while the wettability and ageing effects were studied by WCA (water contact angle measurements). The samples were aged in dry air or in water. In the case of dry air, the least pronounced ageing was observed for the sample treated for 60 s. For samples aged in water, however, the lowest ageing rate was observed for the sample treated for 5 s. The samples were ageing slightly faster in water than in air. We also investigated the temperature effect on ageing of plasma treated samples. A set of samples was stored in a refrigerator at 5 °C and the other set was placed into an oven at 50 °C. The ageing rate of the samples stored at 5 °C was significantly lower than for the samples stored at 50 °C, so cooling the samples help keeping the required surface properties.     

Adhesive properties of polypropylene (PP) and polyethylene terephthalate (PET) film surfaces treated by DC glow discharge plasma

In this study, the adhesive properties of the plasma modified polypropylene (PP) and polyethylene terephthalate (PET) film surfaces have been investigated. Hydrophilicity of these polymer film surfaces was studied by contact angle measurements. The surface energy of the polymer films was calculated from contact angle data using Fowkes method. The chemical composition of the polymer films was analyzed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was used to study the changes in surface feature of the polymer surfaces due to plasma treatment. The adhesion strength of the plasma modified film was studied by T-peel strength test. The results showed a considerable improvement in surface wettability even for short exposure times. The AFM and XPS analyses showed changes in surface topography and formation of polar groups on the plasma modified PP and PET surfaces. These changes enhanced the adhesive properties of polymer film surfaces.     

等离子体表面接枝改性聚对苯二甲酸乙二醇酯的血液相容性研究

利用等离子体表面接枝改性方法在聚对苯二甲酸乙二醇酯(polyethylene terephthalate，PET)材料表面接枝不同分子量的聚乙二醇(PEG)，体外血液相容性实验表明．接枝了PEG的PET材料的血液相容性与PEG的分子量有关；当接枝的PEG分子量达到6000时，材料的血液相容性最好。     

Contact angle analysis of low-temperature cyclonic atmospheric pressure plasma modified polyethylene terephthalate

Polyethylene terephthalate (PET) films are modified by cyclonic atmospheric pressure plasma. The experimentally measured gas phase temperature was around 30 °C to 90 °C, indicating that this cyclonic atmospheric pressure plasma can treat polymers without unfavorable thermal effects. The surface properties of cyclonic atmospheric pressure plasma-treated PET films were examined by the static contact angle measurements. The influences of plasma conditions such as treatment time, plasma power, nozzle distance, and gas flow rate on the PET surface properties were studied. It was found that such cyclonic atmospheric pressure plasma is very effective in PET surface modification, the reduced water contact angle was observed from 74° to less than 37° with only 10 s plasma treatment. The chemical composition of the PET films was analyzed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was used to study the changes in PET surface feature of the polymer surfaces due to plasma treatment. The photoemission plasma species in the continuous cyclone atmospheric pressure plasma was identified by optical emission spectroscopy (OES). From OES analysis, the plasma modification efficiency can be attributed to the interaction of oxygen-based plasma species in the plasma with PET surface. In this study, it shows a novel way for large scale polymeric surface modification by continuous cyclone atmospheric pressure plasma processing.     

A transient mesophase on drawing polymers based on polyethylene terephthalate (PET) and polyethylene naphthoate (PEN)

This paper is centred around the identification of a transient mesophase during the drawing of PET and PEN and their associated random copolymers. While the observation of the mesophase has previously been announced as a note (Macromolecules, 31, 1998, p. 7562), this paper sets out the work in appropriate detail. Samples across the full random copolymer composition range are hot drawn, and, either immediately quenched or examined in-situ using synchrotron radiation. In each case a mesophase has been observed under drawing conditions which produced little or no crystallinity. That the phase was not the product of the quench was confirmed by the high temperature dynamic measurements. The signature of the mesophase is a sharp, meridional peak in the WAXS fibre diagram which shows no other sharp peaks suggesting crystallinity; the equatorial maxima, while equiaxial and indicating a high level of chain orientation, are diffuse. The mesophase is thus classified as smectic A. SAXS measurements on quenched samples, give no indication that the mesophase is associated with a particular microstructure. The mesophase is seen across the PET/PEN composition range, its observation being more straightforward in the random copolymers where the rate of crystallisation is significantly reduced. Subsequent crystallisation of the fibres by suitable annealing, replaces the meridional mesophase peak on the first layer line with off-meridional crystal reflections characteristic of the triclinic unit cell. The layer line is at a slightly lower angle after crystallisation indicating a longer axial repeat in the crystal than in the mesophase. The development of crystallinity gives rise to a distinct SAXS pattern indicative of a two phase microstructure. The transition from smectic A mesophase to triclinic crystal provides a rationale for the occurrence of oblique lamellae in PET, and associated random copolymers with more than 70% ethylene terephthalate units, as indicated by the four point SAXS patterns, and also for the c axis tilt observed in the WAXS patterns. Similarly, for the PEN rich copolymers, the absence of obliquity and consequent c-axis tilt, coupled with the marked layer line streaking of the triclinic reflections, can be rationalised in terms of the c-shear of the transition being compensated by faulting in the crystal.     

Collagen immobilization on polyethylene terephthalate surface after helium plasma treatment

An attractive alternative to add new functionalities such as biocompatibility due to the micro- and nano-scaled modification of polymer surfaces is offered by plasma processing. Many vital processes of tissue repair and growth following injuries depend on the rate of adsorption and self-assembling of the collagen molecules at the interfaces. Consequently, besides the amount of protein, it is necessary to investigate the form in which the collagen molecules are organizing on the polymer surface. In this study, direct current (DC) helium plasma treatment was used in order to obtain poly(ethylene terephthalate) (PET) films with different amounts of collagen and different shapes of aggregates formed from the collagen molecules. The immobilization of collagen on PET surface was confirmed by XPS measurements, an increase of the nitrogen content by increasing the plasma exposure time being recorded. The SEM and AFM measurements revealed the presence of grains and dendrites of collagen formed on the polymer surface. At 15 min plasma treatment time, the polymer surface after collagen immobilization has a homogenous topography. Usually, one can find fibrils, coil or dendrimers of collagen formed in buffer solutions and immobilized on different polymer surfaces. On the other hand, in this particular configuration, the combination of DC plasma and helium gas as a PET functionalization tool is an original one. As the collagen is not covalently immobilized on the surfaces, it may interact with the cell culture medium proteins, part of the collagen might being replaced by other serum proteins.     

Characterization by optical emission spectroscopy of an oxygen plasma used for improving PET wettability

Polymers have excellent bulk physical and chemical properties but usually poor surface properties. For wettability improvement plasma technology is one of the most promising techniques. Several studies about surface modifications of polyethylene terephthalate (PET) exposed to an oxygen plasma have been already carried out. In this work an analysis of the plasma phase by optical emission spectroscopy (OES) has been employed in order to establish a correlation with the surface effects induced by plasma exposition on PET chemical composition and wettability, investigated by X-ray photoelectron spectroscopy (XPS) and water contact angle measurements, respectively. The treatment has been carried out for a time of 60 s at a constant pressure (15 Pa) and at different process powers ranging from 20 to 200 W. As expected, the best performance has been obtained at a power of 200 W due to the larger presence of oxygen radicals (OI) with the assistance of ionic species (OII, O₂⁺) which create dangling bonds on the substrate surface.     

Enhanced photocatalytic activity of TiO2-incorporated nanofiber membrane by oxygen plasma treatment

In this paper, we report on the high-performance photocatalysis of polymeric TiO₂ membranes modified by oxygen plasma treatment for water purification. TiO₂-nanopowder-incorporated poly ε-caprolactone (PCL/TiO₂; PT) nanofibers were prepared by electrospinning at various concentrations of TiO₂ (1, 3, 5, and 7 wt.%) and then treated by atmospheric plasma with oxygen gas (OAP). As the TiO₂ content increased, the surface roughness and photocatalytic efficiency of the nanofibers increased. The tensile strength of the membranes increased until the TiO₂ content reached 3 wt.% but led to a degradation of the mechanical property at higher concentrations owing to significant agglomeration of TiO₂. The hydrophilicity of OAP membranes increased as the TiO₂ nanopowders were exposed and the production of polar species was induced at the surface of the PT nanofibers. The OAP-PT membranes were observed to enhance the degradation of harmful organics. The results indicate that OAP-PT membranes are useful photocatalysts for purifying water.     

Enhanced adhesion of plasma-sputtered copper films on polyimide substrates by oxygen glow discharge for microelectronics

Enhanced plasma-sputtered copper film adhesion onto polyimide substrates treated by oxygen glow discharge was investigated. The peel test demonstrates this improvement, with peel strengths of 0.7-1.2 g/mm for copper films prepared on un-modified polyimide substrates and 195.5-262.2 g/mm for copper films on oxygen plasma-modified polyimide substrates at certain plasma conditions. The enhanced adhesive strengths of plasma-sputtered copper films onto polyimide substrates by oxygen plasmas are due mainly to the increased surface energies of the polyimide substrates. Contact angle measurements indicate that the surface energies of polyimide substrates were greatly increased by oxygen plasmas. X-ray photoelectron spectroscopy analysis shows that the increased surface energies of polyimide substrates using oxygen plasmas occur because of the increased oxygen surface concentration and the increased C-O bond proportion.     

Influence of cold remote nitrogen oxygen plasma treatment on carbon fabric and its composites with specialty polymers

The parameters controlling performance of a fiber-reinforced polymer composite are type of matrix and fibers, their amount, aspect ratio, fiber orientation with respect to loading direction, fiber–matrix interface, and processing technique. In the case of carbon fiber reinforcement, fiber–matrix interface has always been a serious concern, because of chemical inertness of carbon fibers toward matrix and hence efforts are continued to enhance the fiber–matrix adhesion. A recent technique of cold remote nitrogen oxygen plasma was employed for surface treatment of carbon fabric (CF) to enhance its chemical reactivity and mechanical interaction toward matrix material. Untreated and plasma treated CF were used as bidirectional reinforcement for developing high performance composites with various specialty polymer matrices such as Polyetherimide, Polyethersulfone, and Polyetheretherketone. Treated CF reinforced composites showed appreciable improvement in most of the mechanical properties, which varied with type of plasma, its dozing and matrix used. X-ray Photoelectron Spectroscopy confirmed improvement in O/C and N/C ratio indicating inclusion of Oxygen and Nitrogen on the surfaces of fibers due to plasma treatment, which was responsible for enhanced adhesion. Similarly, Fourier Transform Infrared–Attenuated Total Reflectance Spectroscopy indicated presence of ether, carboxylic, and carbonyl functional groups on the plasma-treated surface of fibers. Raman spectroscopy indicated slight distortion in graphitic structure of treated CF. Scanning Electron Microscopy also indicated changes in the topography of treated CF, indicating enhanced mechanical interlocking with matrix.     

Influence of nitrogen microwave radicals on sequential plasma activated bonding

The role of nitrogen microwave (MW) radicals in sequential plasma activated bonding of silicon/silicon has been investigated through contact angle and electron energy loss spectroscopy (EELS) observations. The contact angle for the sequentially activated (using oxygen RIE time for 60 s followed by variable times of nitrogen MW) silicon surfaces was higher than that of the oxygen RIE activated surfaces below 300 s but it was lower than that of the surfaces treated with oxygen RIE for a prolonged activation of 1200 s. The amorphous layer of the sequentially activated interface became thicker compared to the oxygen RIE treated interface and became thinner after prolonged activation using Nitrogen radicals. The EELS measurements showed no nitrogen in the silicon and interfacial amorphous silicon oxide, but showed oxygen deficiency in the amorphous layer.     

无卤阻燃玻纤增强聚对苯二甲酸乙二醇酯(PET)的研制

综合对比了自行研制的无卤阻燃增强PET与传统的卤系增强阻燃PET力学性能、阻燃性能、电性能、结晶性能、耐热性能、流动性.结果表明,在满足相同阻燃要求时,无卤阻燃增强PET和卤系阻燃增强PET的综合力学性能相当;无卤阻燃增强PET的电性能明显优于卤系阻燃增强PET;无卤阻燃增强PET的结晶性能和热稳定性略优于卤系增强阻燃PET;二者的流动性基本相当.     

Balancing the corrosion resistance and through-plane electrical conductivity of Cr coating via oxygen plasma treatment

Developing an electrically conductive and corrosion-resistant coating is essential for metal bipolar plates of polymer electrolyte membrane fuel cells(PEMFCs). Although enhanced corrosion resistance was seen for Cr coated stainless steel(Cr/SS) bipolar plates, they experience a quick decrease of through-plane electrical conductivity due to the formation of a porous and low-conductive corrosion product layer at the plate surface, thus leading to an increase in interfacial contact resistance(ICR). To tackle this issue, the multilayer Cr coatings were deposited using the magnetron sputtering with a remote inductively coupled oxygen plasma(O-ICP) in the present study. After the O-ICP treatment, a Cr oxide layer(Cr O*) is formed on the specimen surface. The Cr O*/Cr/SS has a remarkably lower stable corrosion rate(iss) than that of the native Cr oxides(Cr On/Cr/SS). Compared with Cr On/Cr/SS, the excellent performance of Cr O*/Cr/SS is attributed to a denser and thicker surface layer of Cr O* with Cr being oxidized to its highest valence state,Cr(VI). More importantly, the through-plane electrical conductivity of the specimens treated by the optimized O-ICP decreases much slowly than Cr On/Cr/SS and thus, the increament of ICR of Cr O*/Cr/SS after the potentiostatic polarization test is considerably smaller than that of Cr On/Cr/SS, which is benefited from the reduced issthat mitigates the deposition of corrosion products and hinders further oxidation of Cr coating. Therefore, Cr O*/Cr/SS proves to be a well balanced trade-off between corrosion resistance and through-plane electrical conductivity. The results of this study demonstrate that O-ICP treatment on a conductive metal coating is an effective strategy to improve the corrosion resistance and suppress the increase of ICR over the long-term polarization. The technique reported herein exhibits its promising potential application in preparing corrosion resistant and electrically conductive coatings on metal bipolar plates to be used in PEMFCs.     

聚对苯二甲酸乙二醇酯(PET)的解聚与反应机理研究

对聚对苯二甲酸乙二醇酯(PET)的各种解聚方法的解聚及其机理研究进行了概括性的综述,以期对该领域的研究提供参考和借鉴.同时,本文简要介绍了我们首次利用微波技术在纯水中进行PET解聚的研究工作.     

涤纶膜（PET）表面的氟化处理及其结构的XPS研究

详细描述了ＣＦ４／ＣＨ４混合气体等离子体处理涤纶膜（ＰＥＴ）表面的过程。利用Ｘ光电子能谱（ＸＰＳ）研究处理后ＰＥＴ的表面结构、性质以及处理后样品的浸水行为。结果表明,ＰＥＴ经碳氟等离子体处理后,其表面覆盖上一层具有憎水功能的氟化层,氟化层的结构与碳氟混合气体的组成有关;混合气体等离子体在ＰＥＴ表面形成化学组成均匀、交联结构的处理层;纯ＣＦ４等离子体的处理结果则以刻蚀作用为主,处理层的化学组成不均匀     

Functionalization of single-walled carbon nanotubes by citric acid/oxygen plasma treatment

A safe and simple method of functionalizing single-walled carbon nanotubes (SWCNTs) has been developed, that significantly increases their dispersibility in water. SWCNTs in pure ethanol are treated with a supersonic homogenizer and dried. Then they are wetted with weak citric acid solution. Finally an RF (13.56 MHz) citric acid/oxygen plasma reaction is carried out under optimum conditions. As a result, hydrophilic functional groups attach onto the SWCNT surfaces, which enhance their dispersibility in water. The attachment of functional groups is identified by the FT-IR spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The dispersibility and dispersion stability are studied by the precipitation tests, UV-visible spectroscopy, and transmission electron microscopy. These functionalized SWCNTs are expected to be used in various applications.     

High-density polyethylene functionalized by cold plasma and silanes

High-density polyethylene (HDPE) surface was modified by radio-frequency discharge plasma and subsequently grafted by alkoxy silane to form a new surface containing polar functional groups. Reaction of the polar groups with vinyl silanes significantly improved hydrophilicity of the polymer. The decrease of surface energy of polymer modified by plasma in the course of ageing was stabilized by silane grafting. The changes in chemical structure of the polymer were analyzed by ATR-FTIR spectroscopy, surface roughness was studied using AFM. The surface energy, and its polar contribution of plasma modified HDPE increased, as well as peel strengths of adhesive joints to polyacrylate.     

氧气透平压缩机氮气试车新方法

利用现有中压氮气管网氮气作为氧气透平压缩机的密封气和工作介质,对其进行正式开车前的试车,从而节省调试时间以确保项目顺利进行。详细介绍了氮气试车的气体流路、试车过程及试车过程中的参数。     

Effect of oxygen plasma treatment on low dielectric constant carbon-doped silicon oxide thin films

Low dielectric constant (low k) carbon-doped silicon oxide (CDO) films are obtained by plasma-enhanced chemical vapor deposition. The k value of the as-deposited CDO film is less than 2.9. However, the k value may be changed during the integration process. In integration process, photoresist removal is commonly implemented with oxygen plasma ashing or by wet chemical stripping. In this work, the impact of oxygen plasma treatment has been investigated on the quality of the low-k CDO films. Different plasma treatment conditions, including variable pressure, r.f. power, and treatment time were employed. A variety of techniques, including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), atomic force microscopy (AFM), and scanning electron microscope (SEM) were used to analyze the effect of the oxygen plasma post-treatment on the low-k CDO films. The result indicates that oxygen plasma will damage the CDO film by removing the entire carbon content in the upper part of the film with increasing treatment time, which results in an increase in the k value and film thickness loss. Our result also confirms that with low r.f. power and low pressure, the damage will be less.