Contact angle determination on plasma‐treated poly(ethylene terephthalate) fabrics and foils

The surfaces of polyester (PET) fabrics and foils were modified by low‐pressure RF plasmas with air, CO₂, water vapor as well as Ar/O₂ and He/O₂ mixtures. To increase the wettability of the fabrics, the plasma processing parameters were optimized by means of a suction test with water. It was found that low pressure (10–16 Pa) and medium power (10–16 W) yielded a good penetration of plasma species in the textile structure for all oxygen‐containing gases and gaseous mixtures used. While the wettability of the PET fabric was increased in all cases, the Ar/O₂ plasma revealed the best hydrophilization effect with respect to water suction and aging. The hydrophilization of PET fabrics was closely related to the surface oxidation and was characterized by XPS analysis. Static and advancing contact angles were determined from the capillary rise with water. Both wetting and aging demonstrated a good comparability between plasma‐treated PET fabrics and foils, thus indicating a uniform treatment. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1452–1458, 2006     

Surface modification of Kevlar 149 fibers by gas plasma treatment

Kevlar 149 fibers have been surface treated with NH₃-, 0₂-, or H₂O-plasm to modify the fiber surfaces. SEM (scanning electron microscopy) is used to characterize the surface topography of fibers etched by gas plasmas. The chemical compositions and functional groups of the fiber surfaces are identified by ESCA (electron spectroscopy for chemical analysis) and SSIMS (static secondary ion mass spectroscopy), respectively. The contact angle of water on modified PPTA [poly(p-phenylene terepbthalamide)] film prepared from using Kevlar 149 fibers is also used to investigate the wettability. The results show that the etching abilities of gas plasmas are dependent on the type of gas used for plasma treatments. The contact angle data indicate that all the three gas plasma treatments are effective in rendering the surface of PPTA more hydrophilic. The ESCA analysis results show that the surface compositions of plasma-treated fibers are highly dependent on the type of gas used and treatment time. Changes in surface compositions of fibers treated by NH₃-, O₂-, and H₂O-plasma are observed. Increasing nitrogen and oxygen contents are observed for the NH₃-plasma treatment, and the O₂- and H₂O-plasma treatments, respectively. Furthermore, the incorporation of amino groups into fiber surfaces by NH₃-plasma treatment and the extensive damage of the aromatic ring and the polymer backbone by H₂O-plasma and O₂-piasma are evidenced by SSIMS.     

Gas permeability and permselectivity of plasma‐treated polyethylene membranes

The effects of NH₃‐plasma and N₂‐plasma treatments on rubbery polyethylene (PE) membranes on the permeation behavior for carbon dioxide (CO₂), O₂, and N₂ were investigated with permeability measurements. The NH₃‐plasma and N₂‐plasma treatments on PE membranes increased both the permeation coefficient for CO₂ and the ideal separation factor for CO₂ with respect to N₂. For O₂ transport, both the permeation coefficient for O₂ and the ideal separation factor for O₂ with respect to N₂ were increased. NH₃‐plasma and N₂‐plasma treatments on polymer membranes possibly bring about an augmentation of permeability and permselectivity simultaneously. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 383–387, 2006     

Gas permeability and permselectivity of plasma‐treated polypropylene membranes

The effects of NH₃‐plasma and N₂‐plasma treatment on rubbery polypropylene (PP) membrane upon permeation behavior for CO₂, O₂, and N₂ were investigated from their permeability measurements. The NH₃‐plasma and N₂‐plasma treatment on PP membranes could increase both the permeability coefficient for CO₂ and the ideal separation factor for CO₂ relative to N₂. For O₂ transport, both the permeability coefficient for O₂ and the ideal separation factor for O₂ relative to N₂ also increased. NH₃‐plasma and N₂‐plasma treatment on PP membranes possibly brings about an augmentation of permeability for CO₂ and permselectivity of CO₂ relative to N₂ simultaneously, but unfortunately the plasma‐treated PP membrane does not reach the level of CO₂ separation membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Surface modification of PET films by pulsed argon plasma

The rf power was modulated (discharge on‐time of 10 μs and discharge off‐time of 50–500 μs), for pulsed argon (Ar) and oxygen (O₂) plasmas used to irradiate PET film surfaces to modify the film surfaces. From data regarding the contact angle for the modified PET film surfaces and chemical analyses with XPS, effects of the rf power modulation on the surface modification are discussed. The pulsed Ar and O₂ plasmas are effective in modification of the PET film surface. There is no difference in the contact angle between the pulsed plasma and the continuous plasma. Furthermore, the pulsed Ar plasma is advantageous in formation of hydroxyl groups on the PET film surfaces. The rf power modulation has a possibility to modify into peculiar surfaces. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2845–2852, 2002     

Surface modification of poly(vinylidene fluoride) film by remote Ar, H2, and O2 plasmas

The surface modification of poly(vinylidene fluoride) (PVDF) film induced by remote Ar, H₂, and O₂ plasmas have been investigated using contact angle measurement, X-ray photoelectron spectroscopy, and scanning probe microscope. The contact angle of water shows an improvement in the PVDF surface wettability during short plasma exposure time. Three remote plasmas treated PVDF sheet surfaces occurred dehydrofluorination and oxidation reactions simultaneously. Remote hydrogen plasma was the most effective in defluorination reactions and remote oxygen plasma was unfavorable to abstract fluorine atoms.     

Asymmetric polysulfone gas separation membranes treated by low pressure DC glow discharge plasmas

Asymmetric polysulfone (PSF) gas separation membranes were prepared at different conditions such as non‐solvent concentration, evaporation time (ET) and coagulation bath temperature (CBT). In addition, effects of low‐pressure DC glow discharge plasma on the characteristics of PSF membranes were investigated. PSF membranes both before and after plasma treatment were characterized by several techniques, including contact angle measurement, scanning electron microscope (SEM), dynamic mechanical thermal analysis (DMTA), and atomic force microscopy (AFM). Furthermore, the performance of membranes was evaluated in terms of permeability of CO₂, CH₄, O_2, and N₂ gases. The ideal selectivity of CO₂/CH₄ and O₂/N₂ and surface free energy was calculated. Results showed that the EtOH concentration, ET and CBT affect the morphology of PSF membranes. For membranes prepared from a casting solution consisting of PSF 26.0, NMP 28.0, THF 28.0, and EtOH 18.0 wt % and ET for 3 min, the maximum selectivity of untreated membrane is about 69.76 and 12.59 for CO₂/CH₄ and O₂/N₂, respectively. After plasma treatment, the ideal selectivity is receded; however, the CO₂/CH₄ is still higher than 40.41 at pressure of 5 bars. Finally, preparation conditions and DC glow discharge plasmas have significant effects on the characteristics of the PSF membranes and result in an increase of the gas permeation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42116.     

Surface modification of low‐density polyethylene (LDPE) film and improvement of adhesion between evaporated copper metal film and LDPE

To improve the interfacial adhesion between evaporated copper film and low‐density polyethylene (LDPE) film, the surface of LDPE films was modified by treating with chromic acid [K₂Cr₂O₇/H₂O/H₂SO₄ (4.4/7.1/88.5)]/oxygen plasma. Chromic‐acid‐etched LDPE was exposed to oxygen plasma to achieve a higher content of polar groups on the LDPE surface. We investigated the effect of the treatment time of chromic acid in the range of 1–60 min at 70°C and oxygen plasma in the range of 30–90 sec on the extent of polar groups created on the LDPE. We also investigated the surface topography of and water contact angle on the LDPE film surface, mechanical properties of the LDPE film, and adhesion strength of the evaporated copper metal film to the LDPE film surface. IR and electron spectroscopy for chemical analysis revealed the introduction of polar groups on the modified LDPE film surface, which exhibited an improved contact angle and copper/LDPE adhesion. The number of polar groups and the surface roughness increased with increasing treatment time of chromic acid/plasma. Water contact angle significantly decreased with increasing treatment time of chromic acid/plasma. Combination treatment of oxygen plasma with chromic acid drastically decreased the contact angle. When the treatment times of chromic acid and oxygen plasma were greater than 10 min and 30 sec, respectively, the contact angle was below 20°. With an increasing treatment time of chromic acid, the tensile strength of the LDPE film decreased, and the film color changed after about 10 min and then became blackened after 30 min. With the scratch test, the adhesion between copper and LDPE was found to increase with an increasing treatment time of chromic acid/oxygen plasma. From these results, we found that the optimum treatment times with chromic acid and oxygen plasma were near 30 min and 30 sec, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1677–1690, 2001     

Gas permeability of NH3‐plasma‐treated poly(methyl methacrylate) membranes

The effect of NH₃ plasma treatment on glassy poly(methyl methacrylate) (PMMA) membranes on the diffusion process for penetrant gases (CO₂, O₂, and N₂) was investigated from mean permeability data. The mean permeability coefficient for CO₂ definitely depended on the upstream pressure, whereas those for O₂ and N₂ remained constant regardless of the upstream pressure. For O₂ transport, the permeability increased a little with increasing treatment power, and for N₂ transport, it was not affected by the treatment power. For CO₂ transport, NH₃ plasma treatment promoted the transport of Langmuir mode, presumably through an increased Langmuir capacity constant for CO₂. NH₃ plasma treatment for PMMA membranes resulted in an increase in the separation factor of CO₂ relative to N₂ and in the permeability to CO₂. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1068–1072, 2003     

Enhancement of nitric oxide removal by ammonia on a low-rank coal based carbon by sulphuric acid treatment

This work presents a study of the effect of wet sulphuric acid treatment and gas-phase treatment with SO₂ + O₂ + H₂O on the catalytic activity of a low-rank coal-based carbon for the nitric oxide reduction with ammonia. Carbons were characterized by N₂ adsorption, TPD, and FTIR in order to assess how the surface chemistry and the texture of carbons change after the treatments. A great amount of oxygenated functional groups both CO₂ and CO evolving ones are produced by liquid-phase sulphuric acid treatment. However, the amount of those groups after gas-phase treatment with SO₂ + O₂ + H₂O is lower, in particular the CO₂ evolving groups. The catalytic activity of carbons was examined in a fixed bed reactor at 150 °C in a gas flow containing NO, O₂, N₂ and NH₃, the effluent concentration being monitored continuously during the reaction. The obtained results indicate that an appropriate balance between the type of oxygen functional groups and surface area available to the reactant gas are required to reach high levels of NO conversion.     

Surface characterization of low‐temperature cascade arc plasma–treated low‐density polyethylene using contact angle measurements

Low‐density polyethylene (LDPE) was treated with a low‐temperature cascade arc plasma torch (LTCAT) of argon with or without adding a reactive gas of oxygen or water vapor. The static sessile droplet method and the dynamic Wilhelmy balance method were employed to perform surface contact angle measurement in order to investigate and characterize the effects of LTCAT treatment on LDPE surfaces. These treatment effects included changes in surface wettability and surface stability and possible surface damage that would create low‐molecular‐weight oligomers on the treated surface. Experimental results indicated that the combination of static and dynamic surface contact angle measurements enabled a comprehensive investigation of these effects of plasma treatment on a polymer surface. Without the addition of a reactive gas, a 2‐s argon LTCAT treatment of LDPE resulted in a stable hydrophilic surface (with a water contact angle of 40°) and little surface damage. The addition of oxygen into argon LTCAT produced a less stable LDPE surface and showed more surface damage. Adding H₂O vapor into argon LTCAT produced an extremely hydrophilic surface (with a water contact angle < 20°) of LDPE but with pronounced surface damage. When compared with conventional radio frequency (13.56 MHz) plasmas, LTCAT treatment provides a much more rapid, effective, and efficient method of surface modification of LDPE. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2528–2541, 2006     

Surface modification of nanocrystalline diamond/amorphous carbon composite films

The surfaces of nanocrystalline diamond/amorphous carbon (NCD/a-C) nanocomposite films deposited from a 17% CH₄/N₂ mixture have been subjected to a variety of plasma and chemical treatments, namely H₂ and O₂ microwave plasmas, a CHF₃ 13.56 MHz plasma, and a chemical treatment with aqua regia (HCl:HNO₃ 3:1). The resulting surfaces have been studied with respect to their chemical nature by X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (TOF-SIMS), concerning their morphology with atomic force microscopy, and by contact angle measurements to study their hydrophobicity and their stability. As-grown surfaces are hydrogen terminated, but the number of C–H bonds can slightly be increased by a H₂ microwave plasma, while treatment with aqua regia considerably lowers the number of C–H bonds at the surface. O₂ and CHF₃ plasmas, on the other hand, lead to a replacement of the terminating C–H bonds by C–O or C–OH and C–F_x groups, respectively. Finally, by contact angle measurements over a period of 150 days it could be shown that the H-terminated surface is very stable whereas the contact angle of the O-treated surface changed considerably with time, probably due to the adsorption of contaminants.     

Flue gas desulphurization by activated carbon fibers obtained from polyacrylonitrile by-product

By pyrolysis of a polyacrylonitrile textile by-product, subsequent activation by CO₂ and treatment (at high temperature) with a N₂ flow containing a low percentage of O₂ or of NH₃, three carbonaceous matrices are obtained having a high surface area and surface sites with basic characteristics. The SO₂ sorption properties of these carbon samples (in the temperature range between 100 and 160 °C) from gaseous mixtures having a similar composition to flue gases, seems to be promoted by nitrogen bonded to carbon. The SO₂ adsorbed by the carbons can be divided, by suitable extraction with distilled water, into: (i) desorbable, such as SO₂ or H₂SO₃, (ii) desorbable, such as SO₃ or H₂SO₄, (iii) non-desorbable. Following 10 SO₂ adsorption and desorption cycles, the surface area values of the activated carbons remain practically constant, while both the content of the acidic surface sites and the amount of non-desorbable SO₂ increase; this results in the decrease in the SO₂ carbon sorption property seeming to be even more marked for the carbon sample containing nitrogen.     

Electrochemical properties of polypropylene membranes modified by the plasma polymerization coating of SO2/acetylene

Polypropylene membranes were modified by the plasma etching of SO₂, SO₂? O₂, or SO₂? H₂O, followed by the plasma polymerization coating of SO₂/acetylene. The conditions for SO₂ plasma etching were optimized by the measurement of the ion‐exchange capacity (IEC) as a function of the plasma‐etching power (10–30 W), gas pressure (40–60 mTorr), and treatment time (15–120 s). For the plasma etching of SO₂? O₂ and SO₂? H₂O, only the pressure ratio (SO₂/O₂ and SO₂/H₂O) was optimized under the optimized conditions determined from SO₂ plasma etching. Plasma etching was then combined with the plasma polymerization coating of SO₂/acetylene, for which the conditions were again optimized by the measurement of the IEC as a function of the plasma power (10–40 W), chamber pressure (50–200 mTorr), SO₂/acetylene ratio (15/135–60/90), and treatment time (0–10 min). Next, the electrical resistance and water uptake were evaluated. The modified membranes were also analyzed with scanning electron microscopy, whereas plasma polymer coatings were characterized with Fourier transform infrared/attenuated total reflection. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3692–3699, 2006     

A new approach for selective surface modification of fluoropolymers by remote plasmas

Ethylene‐co‐tetrafluoroethylene (ETFE) and poly (vinylidene fluoride) (PVDF) films were exposed to the remote Ar, H₂, and O₂ plasmas. The modified polymer surfaces were characterized by X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurement. The plasma exposure led to weight loss and changes in the chemical composition on the polymer surface. Selective surface modification of fluoropolymers introduces various functional groups without altering the bulk properties. The results may be summarized as follows: the remote hydrogen plasma was the most effective in alternation from C? F to C? H (abstraction of fluorine). On the other hand, the remote oxygen plasma was unfavorable to abstract fluorine atoms, but effective in dehydrogenation (abstraction of hydrogen). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1012–1020, 2004     

Comparison of fibroblast and nerve cells response on plasma treated poly (L‐lactide) surface

Plasma technique can easily be used to introduce desired functional groups or chains onto the surface of materials, and so it has a special application to improve the cell affinity of polymers surfaces. The purpose of this study is to elucidate the interaction between the cells and the surface of crystalline poly (L ‐lactide) (PLLA) samples, which were modified using a low‐temperature plasma treatment apparatus. The plasma treatments were carried out in the carbon dioxide (CO₂) gas. The results showed that the contact angle of the samples, which was plasma treated in CO₂ gas, decreased compared with that of the untreated samples. The hydrophilicity increased because of the introduction of oxygen‐containing functional groups onto the PLLA surfaces according to the spectroscopy for chemical analysis. High quantities of ? C? O groups, such as hydroxyl and carboxyl could be in corporate into the surface of PLLA. The surface wettability, topography, and chemistry of treated PLLA samples were characterized by contact angle measurement, scanning electron microscope (SEM), and ATR‐FTIR spectroscopy. The origin and plasma‐treated samples were used to investigate the interaction of two different types of cells namely, B65 glial nervous, and L929 fibroblast cells. The nervous cell response on the PLLA plasma treated in the CO₂ gas were significantly superior to that of the L929 fibroblast cells and untreated one. The surface modification technique used in this study may be applicable to tissue engineering for the improvement of nerve tissue compatibility of polymer and scaffold‐type substrates. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Plasma surface modification of poly(phenylene sulfide) films for copper metallization

Poly(phenylene sulfide) (PPS) films were modified by Ar, O₂, N₂ and NH₃ plasmas in order to improve their adhesion to copper metal. All four plasmas modified the PPS film surfaces, but the NH₃ plasma modification was the most effective in improving adhesion. The NH₃ plasma modification brought about large changes in the surface topography and chemical composition of the PPS film surfaces. The peel strength for the Cu/plasma-modified PPS film systems increased linearly with increasing surface roughness, R _a or R _rms, of the PPS film. The plasma modification also led to considerable changes in the chemical composition of the PPS film surfaces. A large fraction of phenylene units and a small fraction of sulfide groups in the PPS film surfaces were oxidized during the plasma modification process. Nitrogen functional groups also were formed on the PPS film surfaces. The NH₃ plasma modification formed S—H groups on the PPS film surfaces by reduction of S—C groups in the PPS film. Not only the mechanical interlocking effect but also the interaction of the S—H groups with the copper metal may contribute to the adhesion of the Cu/PPS film systems.     

Plasma modification of poly(oxybenzoate-co-oxynaphthoate) film surfaces for copper metallization

Poly(oxybenzoate-co-oxynaphthoate) (POCO) film surfaces were modified by four plasma gases, Ar, O₂, N₂ and NH₃, and the effects of the plasma modification were investigated in order to understand the adhesion with copper metal. The Ar, O₂, N₂ and NH₃ plasmas converted the POCO surfaces from hydrophobic to hydrophilic. The effect of the plasma on the hydrophilic modification was in the order: Ar plasma > O₂ plasma > N₂ plasma > NH₃ plasma. The plasma modification contributed to the adhesion between the deposited copper metal and the POCO film. The NH₃ plasma was most effective in improving the adhesion, and the Ar plasma was ineffective. The plasma-modified POCO film surfaces showed quite different C_ls spectra from that of the original POCO film. There were large differences in the C_ls and N_ls spectra between the NH₃ and Ar plasma modifications. The NH₃ plasma modification did not show C_ls component #5 due to π–π^* shake-up satellite, but the Ar plasma modification did show this component. Furthermore, NH₃ plasma modification led to a new N_ls spectrum. The plasmas caused etching of the POCO film surfaces, and the etch rate depended on what plasma was used and how much RF power was used. The NH₃ plasma-modified POCO film surface showed a larger R _a (25.5 nm) than the other plasma-modified surfaces (R _a = 16.4–19.0 nm), which were comparable to that of the original surface (R _a = 14.8 nm). The NH₃ plasma led to a highly-undulated surface, and the other plasmas did not alter the surface roughness. The roughened surfaces showed contribution to enhancement of the adhesion to the deposited copper metal.     

Wettability of poly(ethylene terephthalate) film treated with low‐temperature plasma and their surface analysis by ESCA

The surface of poly(ethylene terephthalate) (PET) film was modified by low‐temperature plasma with O₂, N₂, He, Ar, H₂, and CH₄ gases, respectively. After being treated by low‐temperature plasma, their surface wettability and chemical composition were investigated by means of electron spectroscopy for chemical analysis (ESCA) and contact angle measurement. The result shows that the surface wettability of PET can be improved by low‐temperature plasma, and the effect of the modification is due mainly to the kind of the gases. Mainly because of the contribution of hydrogen bonding force γ[STACK]^c_S[ENDSTACK], the surface wettability of PET treated with O₂, N₂, He, and Ar plasma for a short time (3 min) increase sharply, and the surface wettability is also improved by H₂ plasma treatment; but the CH₄ plasma treatment does not improve the wettability of PET. ESCA shows that the effect of wettability of PET is tightly related to the presence of polar functional groups that reside in the outermost surface layer of PET. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1327–1333, 1999     

Kinetics of SO2 Removal from Flue Gas on CuO/Al2O3 Sorbent Catalyst

The dependence of SO₂ removal on Cu loading, SO₂ concentration, and temperature are studied experimentally on a thermo‐balance using a series of CuO/Al₂O₃ catalysts in the fresh state as well as in a NH₃‐regenerated state. A kinetic study on SO₂ removal is then carried out using a surface model, which assumes the SO₂ removal rate is being controlled by a surface chemical reaction and takes into account the effect of SO₂ adsorption and consumption of surface CuO. The difference in SO₂ removal between fresh and regenerated CuO/Al₂O₃ is expressed by a parameter n, which is similar to the order of a reaction. The effect of SO₂ adsorption is expressed in the Langmuir‐Hinshelwood form. The results show that the SO₂ removal behavior of NH₃‐regenerated CuO/Al₂O₃ is different from that of fresh CuO/Al₂O₃ and the developed model describes the SO₂ removal behavior well.