The art of surface modification of synthetic polymeric membranes

The development in the area of surface modification of polymeric synthetic membranes since 2000 is reviewed. Many patents, articles, and reviews have been written on the development in the area of surface modification of polymeric synthetic membranes subjected to RO, UF, NF, gas separation (GS), and biomedical applications, mainly since 2000, but recently more attention has been given to the modification of their surfaces to obtain desirable results. In particular, most emphasis has been given to plasma treatment, grafting of polymers on the surface, and modifying the surfaces by adding SMMs (surface‐modifying molecules). New additives are synthesized to make the polymeric membrane surfaces either to be more hydrophilic or hydrophobic, aimed at improvement in selectivity and permeability of the membranes for GS, NF, and RO. Improvement in antifouling by surface modification is also a popular topic in the membrane industries. In the last 8 years, tremendous research efforts have been made on the development of antifouling membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Different surface treatments to improve the adhesion of polypropylene

Injection-molded samples of polypropylene were exposed to oxygen plasma and SACO (SAndblasting and COating) treatments. The pretreated surfaces were successively adhesively bonded or lacquered. The adhesion strength and failure mode of these specimens were examined. The surfaces obtained after treatments were characterized by electron spectroscopy for chemical analysis (ESCA), contact angle measurements, and scanning electron microscopy (SEM). Both microroughness and chemical modification of the surface led to an increase in adhesion by up to a factor of 10. The stability of the surface changes generated during the plasma and SACO pretreatments was observed by different kinds of aging experiments in air and water. The aging of SACO-treated surfaces led to no significant change on the surface. In the case of plasma-treated surfaces, hydrophobic recovery during aging in air reduced the polarity of the surface layer. During aging in water, no hydrophobic recovery on the surface was observed.     

Influence of temperature and relative humidity on aging of atmospheric plasma jet treatment effect on ultrahigh-modulus polyethylene fibers

The aging effects of atmospheric pressure plasma treated fiber surfaces are important for storage and processing of the fibers. One of the high-performance fibers, ultrahigh modulus polyethylene (UHMPE) fiber, was chosen as a model system to investigate the aging process of atmospheric pressure plasma jet (APPJ) treated fibers surfaces 0, 7, 15 and 30 days after initial plasma treatment. The fiber was first plasma-treated and then stored at temperatures varying from ?80 to 80°C on the same relative humidity (RH, 0%) and on RH of 0%, 65% and 100% at the same temperature of 20°C. Immediately after the plasma treatment, scanning electron microscope (SEM) showed the roughened fiber surface. X-ray photoelectron spectroscopy analysis showed changed surface chemical compositions. Contact-angle measurement showed increased surface wettability and microbond test showed an increase in IFSS. With increasing relative humidity or decreasing temperature, the IFSS value decreased and the contact angle increased more slowly. However, after 30 days, the IFSS values and contact angles reached a similar level for all groups. Moisture showed no effect on the single fiber tensile strengths during aging. The reasons for the observed aging behavior could be that decreasing temperature or increasing relative humidity hindered the surface rearrangement of polymer chains after plasma treatment.     

介质阻挡放电在芳纶表面改性中的应用

综述了介质阻挡放电应用于芳纶表面改性研究的最新进展;介绍了介质阻挡放电的机理、特点以及国内主要的介质阻挡放电等离子体的设备;阐述了介质阻挡放电对芳纶亲水性能和粘结性能等表面性能的改善。指出芳纶等离子体表面改性的时间效应限制了其广泛应用,应进一步加强纤维表面等离子体改性的机理研究。     

Evolution of the surface composition and topography of perfluorinated polymers following ammonia-plasma treatment

Treatment of fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) in ammonia plasmas produced surfaces with very high wettability by water, but on storage in air at ambient temperature, the air/water contact angles increased markedly. The evolution of the surface composition and topography was studied by angle-dependent X-ray photoelectron spectroscopy (XPS), derivatization of amine groups with fluorescein isothiocyanate, scanning tunelling microscopy (STM), and atomic force microscopy (AFM). XPS demonstrated a continuous increase in the oxygen content over periods of weeks; this was assigned to oxidation of trapped radicals and subsequent secondary reactions. In addition, the fluorine content also changed markedly on storage; the XPS fluorine signal suggested that there was a substantial amount of fluoride in the freshly treated surfaces, and this component disappeared rapidly on storage. STM and AFM showed no changes in topography with aging but suggested surface hardening on plasma treatment. The events following treatment of FEP and PTFE in ammonia plasmas are not adequately described by a model involving plasma-induced, instantaneous chemical modification followed by surface restructuring; the surface and sub-surface compositions evolve over a period of several weeks due to the occurrence of oxidative reactions, and these chemical changes interact with the physical process of surface restructuring.     

Surface modification of polytetrafluoroethylene films by plasma pretreatment and graft copolymerization to improve their adhesion to bismaleimide

BACKGROUND: Polytetrafluoroethylene (PTFE) is utilized in many engineering applications, but its poor wettability and adhesion properties with other materials have limited its use. The study reported was aimed at achieving surface modification of PTFE films by radiofrequency NH₃ and N₂ plasma treatment, followed by graft copolymerization, in order to improve the interfacial adhesion of PTFE and bismaleimide. RESULTS: X‐ray photoelectron spectroscopy results showed that a short‐time plasma treatment had a distinct defluorination effect and led to nitrogen functional group formation. The nitrogen chemical bonding form was different for NH₃ and N₂ plasma treatments. Under the same experimental conditions, the NH₃ plasma exhibited a better etching effect than did the N₂ plasma. Contact angle measurement showed an improvement in both surface energy and wettabliity by short‐time plasma treatment. The concentration of the surface‐grafted bismaleimide on PTFE increased after the plasma pretreatment. The lap shear strength between PTFE and bismaleimide increased significantly after surface modification. CONCLUSION: This study found that plasma treatment caused changes in surface chemistry, thus leading to an increase of the wettability of PTFE surfaces. Hence, the adhesion properties of PTFE with bismaleimide were significantly improved. Copyright © 2008 Society of Chemical Industry     

Surface free energy changes of stainless steel after one atmospheric pressure plasma treatment

Stainless steel plates (AISI 304L) were treated by an atmospheric pressure plasma treatment at room temperature in order to modify the surface properties. After plasma treatment, the surface wettability and the surface free energy were both improved. The wettability and the surface free energy of stainless steel plates before and after plasma treatment were measured from the results of contact angle test. Through the results of contact angle and surface free energy, optimum plasma treatment conditions were obtained, such as the treatment time of 60 sec and the treatment power of 120 W. In addition to this, the optimum aging time was 3 to 5 min in air.     

Improvement of performance of polyamide reverse osmosis membranes using dielectric barrier discharge plasma treatment as a novel surface modification method

In this research, surface modification of aromatic polyamide thin film composite (TFC) reverse osmosis (RO) membranes was carried out using dielectric barrier discharge (DBD) plasma treatment to improve the performance and fouling resistance of prepared RO membranes. First, polyamide TFC RO membranes were synthesized via interfacial polymerization of m‐phenylenediamine and trimesoyl chloride monomers over microporous polysulfone support membrane. Next, the DBD plasma treatment with 15 s, 30 s, 60 s, and 90 s duration was used for surface modification. The surface properties of RO membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), SEM, AFM, and contact angle measurements. The ATR‐FTIR results indicated that DBD plasma treatment caused hydrogen bonding on the surface of RO membranes. Also, the contact angle measurement showed that the hydrophilicity of the membranes was increased due to DBD plasma treatment. The changes in the membranes surface morphology indicated that the surface roughness of the membranes was increased after surface modification. In addition, it was found that the DBD plasma treatment increased the water permeation flux significantly and enhanced sodium chloride (NaCl) salt rejection slightly. Moreover, the filtration of bovine serum albumin revealed that the antifouling properties of the modified membranes had been improved. POLYM. ENG. SCI., 59:E468–E475, 2019. © 2018 Society of Plastics Engineers     

Hydrophobic recovery and misting behavior of plasma treated PS and PC surfaces

Oxygen plasma treatments of transparent polymers such as polystyrene (PS) and polycarbonate (PC) were performed. Then the hydrophobic recovery of treated surfaces and its effect on their misting behavior was studied. Surface investigations, such as XPS and water contact angle measurements, were combined with the characterization of misting behavior by light transmission methods. In the case of PS it was found that the composition and wettability of the surface layer is insensitive to extraction in water. Hydrophobic recovery leads to decreases of advancing angles upon aging by a mechanism involving macromolecular motions. Misting follows rather closely the behavior of water advancing angles. Oxygen plasma treatment of PC surfaces induces the formation of low molecular weight species which can be extracted by water. Both non-extracted and extracted surfaces were found to undergo hydrophobic recovery with the same mechanism observed in the case of PS. In both cases the misting behavior can be well explained on the basis of wettability.     

Effect of fiber surface morphology on the hydrophilicity modification of cold plasma‐treated polypropylene nonwoven fabrics

Cold oxygen plasma was employed to give hydrophilicity modification to polypropylene (PP) nonwoven fabric (NWF). It was found that, after plasma treatment, PP NWF made from fibers with smooth surfaces can only keep its hydrophilicity for a short time and then shows a quick hydrophobic recovery at room temperature. However, this hydrophilic property can last for a long time in the case of the PP NWF made from fibers with rough surfaces. To prove the contribution of the rough surface to the long‐term hydrophilicity, this PP NWF was treated in an organic solvent to smooth the fiber surface. The hydrophilic feature of this PP NWF no longer lasts for a long time after the same plasma treatment. This observation strongly supports our opinion that the fiber surface morphology of PP NWF is a critical factor for long‐term hydrophilicity improvement after plasma treatment, which gives a positive solution to overcoming the aging effect of hydrophilicity modification often found in this technique. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of plasma treatments on wettability of polysulfone and polyetherimide

Experimental results on plasma treatments of polysulfone and polyetherimide to improve the wettability of these polymers are presented. The plasma is characterized by optical emission spectroscopy. The wettability of the polymer surfaces were checked by contact angle measurements and ESCA is used to compare the surfaces before and after plasma treatment. Correlations between contact angle, concentration of oxygen at the surface, and optical emission intensity of the OH radical have been established. Optimization of operational plasma parameters leading to the best wettability of the treated samples is reported.     

Effect of argon plasma treatment on hydrophilic stability of nanofiber webs

This paper provides a comprehensive analysis of microwave‐induced low‐vacuum argon plasma treatment effects on the hydrophilic stability of various polymeric nanofiber webs. After plasma modification, samples are kept dry at room temperature in a dark place for the experiments, and the wettability of the nanofibers is improved by plasma treatment. The stability of the plasma‐treated hydrophilic nanofiber webs is observed for 55 days using water contact angle measurements. Different polymeric nanofiber webs show different stability. Based on the contact angle measurements, the surface starts to lose hydrophilicity during the first week after plasma treatment. The structural changes are examined by pore size measurements, scanning electron microscopy, and Fourier transform infrared spectroscopy. Two of the selected nanofiber webs are used as microfilters for separation of oily wastewater with a cross‐flow separation unit to measure the effect of the plasma treatment under wastewater. The permeability and selectivity of the plasma‐treated and untreated samples are compared. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46751.     

微通道内表面性质对其内流体流动特性的影响

通过对玻璃微通道内壁表面进行羟基化处理、溶胶-凝胶法纳米SiO2颗粒沉积以及疏水分子自组装等改性处理,制备得到了具有不同内壁表面润湿性和粗糙度的微通道;系统研究了微通道内表面性质对其内流体流动特性的影响。结果表明,在微通道内表面浸润性相同(同为亲水或疏水)时,粗糙表面会比光滑表面给微通道内的流体流动带来更大的阻力,而且流体流动推动力越大时其影响越大;当微通道内表面粗糙度相同时,亲水表面会比疏水表面给微通道内的流体流动带来更大的阻力,而且流体流动推动力越大时其影响越显著;相比之下,微通道内表面浸润性对其内流体流动的影响比其粗糙度的影响更大。研究结果可以为微流动系统或微流体机械的设计和应用提供指导。     

真空氧等离子体表面改性涤纶织物研究

采用真空氧等离子体对涤纶织物进行表面改性,探讨不同处理压强、处理时间下织物润湿性能和分散染料染色性能的变化。使用X射线光电子能谱技术研究了织物表面处理前后化学组成及元素含量的变化,利用扫描电子显微镜表征了处理后织物表面形貌的变化。结果表明:真空氧等离子体处理后的涤纶织物表面氧元素的含量从24.1%上升到40.7%,表面粗糙程度提高;同时织物的润湿性能提高,润湿时间由1680s下降到51s;等离子体处理后涤纶织物的分散染料染色性能改善,其表面深度值由12.3增加为15.6,透湿量由2941g/(m~2·d)增加为3282g/(m~2·d)。     

DBD等离子体改性芳纶表面的动态工艺研究

采用介质阻挡放电(DBD)空气等离子体,选择不同放电强度及处理时间对芳纶表面进行连续动态处理。通过扫描电镜以及光电子能谱仪对处理前后芳纶表面进行表征。结果表明,经DBD等离子体处理后的芳纶表面粗糙度有较大提高,浸润性显著提高,且纤维表面C元素质量分数下降超过5%,0元素质量分数约上升8%;芳纶表面的粗糙度、浸润性及含氧基团含量均随放电强度和处理时间的增加而提高。     

Surface Dynamics vs. Adhesion in Oxygen Plasma Treated Polyolefins

Polyethylene (PE) and polypropylene (PP) were oxygen plasma treated and aged in carefully reproducible conditions. The effect of aging on the surface chemistry, wettability and adhesion were studied using a combination of techniques: contact angle measurements, XPS, SSIMS, adhesion tests (shear and pull).

PE was found to be relatively insensitive to aging both in terms of wettability and adhesion, due to crosslinking during plasma treatment, which is likely to reduce macromolecular mobility within the surface layer.

In the case of PP, dramatic decreases of wettability occur with time, due to macromolecular motions leading to minimization of oxygen-containing functions at the surface. This behavior was shown to affect the adhesion performance of treated PP.     

Altering a polymer surface chemical structure by an ion-assisted reaction

A new surface modification technique, the so-called ion-assisted reaction (IAR), has been developed; such modification of polymer surfaces offers many industrial applications. The addition of new functional groups on polymer surfaces and permanent hydrophilic polymer surfaces (water contact angle below 30° and surface energy 60-70 mJ/m²) have been accomplished by IAR treatment. The formation of functional groups is significantly dependent on the flow rate of the reactive gas, the irradiating ion dose, and the ion beam energy. Improvements in wettability and surface energy are primarily attributed to the increase of polar characteristics due to the formation of functional groups such as —(C=O), —(C=O)—O—, —(C—O)—, etc. The characteristics of the IAR treatment have been reviewed, with outstanding results regarding the wettability and adhesion of various polymers such as PMMA, PC, PP, PS, PI, PVDF, and PTFE.     

Effect of laser surface texturing on primary stability and surface properties of zirconia implants

The aim of this study was to investigate the influence of different laser surface texturing parameters on static and dynamic coefficient of friction values of Yttria-tetragonal zirconia polycrystals (3Y-TZP) against bone to assess the primary stability of implants. The ability of the textures to promote osseointegration, as measured by wettability, and eventual changes in roughness, due to possible aging during sterilization, were also assessed. 3Y-TZP disks were divided into four groups: as sintered sample, sandblasting and etching treatment, laser irradiation using two output power of 0.9 and 1.8 W. The friction tests were carried out by using a pin-on-plate configuration, being the pins the 3Y-TZP disks and the plates the bone. The surfaces were inspected by SEM/EDS and by surface roughness profilometer. Wettability characteristics were also evaluated by drop contact angle, and aging was assessed, after laser treatments, by XRD analysis. Results demonstrate that with laser surface texturing of zirconia it is possible to combine better wettability, better aging performance, and better primary stability, as compared to traditional - Sand blasting and Etching treatments. Thus, it is shown that the laser irradiation technique is a promising alternative to conventional sandblasting and etching procedures.     

Wettability Modification of Nanomaterials by Low-Energy Electron Flux

Controllable modification of surface free energy and related properties (wettability, hygroscopicity, agglomeration, etc.) of powders allows both understanding of fine physical mechanism acting on nanoparticle surfaces and improvement of their key characteristics in a number of nanotechnology applications. In this work, we report on the method we developed for electron-induced surface energy and modification of basic, related properties of powders of quite different physical origins such as diamond and ZnO. The applied technique has afforded gradual tuning of the surface free energy, resulting in a wide range of wettability modulation. In ZnO nanomaterial, the wettability has been strongly modified, while for the diamond particles identical electron treatment leads to a weak variation of the same property. Detailed investigation into electron-modified wettability properties has been performed by the use of capillary rise method using a few probing liquids. Basic thermodynamic approaches have been applied to calculations of components of solid–liquid interaction energy. We show that defect-free, low-energy electron treatment technique strongly varies elementary interface interactions and may be used for the development of new technology in the field of nanomaterials.     

Contact angle and wettability of hybrid surface-treated metal adherends

Adhesion performance of adhesively bonded metal joints with aluminum and stainless steel was much dependent on the surface treatment of the adherends. This work was aimed at optimizing hybrid surface treatments to improve wettability of metal surfaces and strength of adhesive metal joints, which was a combination of mechanical, chemical, and energetic surface treatment methods. The surface free energies and wettability of hybrid surface-treated metal adherends were measured for different treatment conditions with abrasion, grit blast, sulfuric acid etching, phosphoric acid anodizing, silane treatment, plasma treatment, and flame treatment. The surface morphology and chemical composition of the metal adherends were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy and the bond strengths of the single-lap joints composed of aluminum and stainless steel adherends were measured with respect to hybrid surface treatment conditions. From the experiments, an effective hybrid surface treatment condition was suggested for metal surfaces with super-hydrophilic characteristics. Also, the failure mode of adhesive metal joints was evaluated by photo-surface analysis method.