The industrial use of polypropylene (PP) films is limited because of undesirable properties such as poor adhesion and printability. In the present study, a DC glow discharge plasma has been used to improve the surface properties of PP films and make it useful for technical applications. The change in hydrophilicity of modified PP film surface was investigated by contact angle (CA) and surface energy measurements as a function of exposure time. In addition, plasma-treated PP films have been subjected to an ageing process to determine the durability of the plasma treatment. Changes in morphological and chemical composition of PP films were analyzed by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The improvement in adhesion was studied by measuring T-peel and lap shear strength. The results show that the surface hydrophilicity has been improved due to the increase in the roughness and the introduction of oxygen-containing polar groups. The AFM observation on PP film shows that the roughness of the surface increased due to plasma treatment. Analysis of chemical binding states and surface chemical composition by XPS showed an increase in the formation of polar functional groups and the concentration of oxygen content on the plasma-processed PP film surfaces. T-peel and lap shear test for adhesion strength measurement showed that the adhesion strength of the plasma-modified PP films increased compared with untreated films surface.

The experimental work reported here is devoted to the electrical study of two atmospheric pressure dielectric barrier discharge (DBD) reactors operating at high gas flow, conceived for surface treatment applications in spatial afterglow conditions. Both reactors are of coaxial geometry with the dielectric covering the active electrode, and are driven by a power generator delivering quasi-sinusoidal voltage waveforms in the 100–160 kHz range. The influence of the gas flow value and of the input power on the electrical operation of these systems is investigated. The comparative study performed here, by means of electrical measurements, reveals the influence of parameters such as geometrical dimensions and dielectric material used on the operation of the DBD. Power factor measurements are used to quantify the reactors' electrical performance. Optical diagnostics and kinetic modelling reveal a high chemical activity of the systems appropriate for the treatment of surfaces at atmospheric pressure.

Three methods of manipulating wetting data appear satisfactory in providing estimates of the components of solid surface free energy due to dispersion, Keesom, and hydrogen-bonding forces. These include: an extension of the Hansen method with contact angle data, which had been applied to solubility parameters, to surface free energy calculations; Hansen plots of absorption volume data; and Zisman plots using the components of surface tension rather than total surface tension. The Fowkes equation for the dispersion component of surface free energy agrees well with the results from the empirical methods. Extensions and modifications of the Fowkes equation to provide the polar components of solid surface free energy have not worked well when evaluated with a wide range of reference liquids.

Samples of polyethylene and polypropylene have been submitted to repeated short duration (75 ms) flame treatments, at optimum flaming conditions. Surface energies of untreated and flamed specimens were determined by liquid contact angle measurements. It appears that the surface energy of polyethylene increases much more than that of polypropylene after flame treatment. The flamed polymer surfaces were further examined by electron spectroscopy, Fourier Transform IR spectroscopy and secondary ions mass spectrometry. The adhesion properties of modified polymer surfaces were studied by testing in peel the bonded Styrene Butadiene Rubber/polyolefins assemblies. Scanning electron microscopy (SEM) and water contact angle measurements have been used to observe the locus of failure. Good correlations were obtained between surface energy and adhesion strength, the increase in adhesion strength being particularly important for flamed PE/SBR assemblies. In addition, the peeling in a liquid medium allowed the determination of the respective contribution to adhesion of chemical and physical interactions. It is shown that a major part of the adhesion strength increase is of chemical origin, particularly for the bonded flamed PE/SBR assemblies.

In this work, the surface modifications of various polymer films due to helium–oxygen dielectric barrier discharge (DBD) exposure operating under atmospheric pressure are reported. The polymer films studied include ultra high molecular weight polyethylene, polyamide, polytetrafluoroethylene and polyimide. Experimental results reveal increased hydrophilicity and surface energy of the plasma exposed polymers. This is attributed to the presence of oxygen containing groups grafted onto the surface during plasma treatment, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Scanning electron microscopy (SEM) data show the appearance of micro depressions, the size of which depends on the chemical structure and the treatment time, suggesting that mild etching occurs in a predicted fashion. Most importantly, this uniform modification occurs within a few seconds of exposure, time comparable to continuous on-line industrial processing.

In this work, polyamide (Nylon 6) fibers and films were treated under atmospheric pressure glow discharges (APGD) and the effects on the morphology and chemistry of the material were studied. The fibers were plasma treated with N ₂ , C ₂ H ₂ in He for (0.6–9.6) s at a frequency of 90 kHz, leading to the functionalization of the surface through the addition of new reactive chemical groups such as –COOH and –OH and changing the energy, chemical composition and wettability of the surface.Surface characteristics were examined via contact angle measurements, XPS, and SEM. Wettability tests revealed the improvement of the hydrophilic character of the surface as the water contact angle measured after the plasma treatments significantly decreased. The corresponding changes of the total surface energy were evaluated with a dynamic contact angle analysis system revealing a significant increase due to the exposure that can be mainly attributed to the increase of its polar component. Preliminary XPS results show a significant increase in oxygen content with the addition of carboxylic and hydroxylic groups and a decrease in the carbon content of the surface. Most importantly, the plasma modified nylon fibers and films exhibit a stable wetting behavior, even for weeks after being treated, suggesting that it is a promising technique to minimize aging phenomena.

The flame treatment of polypropylene (PP) film involves the use of impinging, conical flames to oxidize the surface of the PP. Depending on treatment conditions, the PP film can be exposed to an inhomogeneous environment because of the conical shape of the flames. This environment can lead to cross-web variations, or 'lanes', in the wettability of the film. We have developed a simple method to quantify these non-uniformities using the information provided by the Wilhelmy plate technique of dynamic contact angle measurement. Both surface-averaged and spatially resolved surface-energy data can be obtained by this technique. In the case of our PP film, the spatial nonuniformities were found to be caused by variations in surface chemistry, not topography. These nonuniformities are not observed on untreated PP. Use of this method enables a quantitative evaluation of the effects of flame-treatment process variables on treatment uniformity.

Polymers such as rubbers generally have low surface energy, thus high hydrophobicity and inherent low bondability. An atmospheric pressure ejected plasma (APEP) source is developed for pre-treatments of polymers to overcome these intractable properties and improve the adhesion ability between polymers as environmental-friendly and simple alternative methods to conventional treatments in spite of several limitations until now. Proper operational conditions are found by T-peel tests performed with various plasma parameters and high peel strength up to 3.5 kgf/cm is achieved at those conditions. Optical emission spectroscopy revealed that the amount of oxygen radicals and gas temperatures are found to be higher at proper conditions in T-peel tests and Fourier transform infrared spectroscopy using attenuated total reflection. Scanning electron microscopy is used for the measurement of surface composition and morphology of pre-treated polymer specimen. These results established the advantage of pre-treatments by APEP source in proper operation conditions when compared to the conventional treatments in terms of improvement of the adhesion ability between polymers.

The surface of polyimide (PI) films before/after plasma surface treatment using a remote-type modified dielectric barrier discharge was investigated to improve the adhesion between the PI substrate and the metal thin film. Among the plasma treatments of the PI substrate surface using various gas mixtures, the surface treated with the N-2/He/SF6/O-2 plasma showed the lowest contact angle value due to the high C=O bondings formed on the PI surface, while that treated with N-2/He/SF6 showed the highest contact angle value due to the high C-F-x chemical bondings on the PI surface. Specifically, when the O-2 gas flow was varied from 0 to 2.0 slm in the N-2(40 slm)/He(1 slm)/SF6(1.2 slm)/O-2 (x slm) gas composition, the lowest contact angle value of about 9.3 degrees was obtained at an O-2 gas flow of 0.9 slm. And it was due to the high content of oxygen radicals in the plasma, which leads to the formation of the highest C=O bondings on the PI surface. When the interfacial adhesion strength between the Ag film and PI substrate was measured after the treatment with N-2(40 slm)/He(1 slm)/SF6(1.2 slm)/O-2(0.9 slm) followed by the deposition of Ag, a peel strength of 111 gf/mm was observed, which is close to the adhesion strength between a metal and the PI treated by a low pressure plasma.

Surfaces of poly(ethylene terephthalate); PET, films were irradiated with Ar⁺ at 1 keV using various ion doses (ID) from 10¹⁴ to 10¹⁷ ions/cm² (isc) with and without an O₂ environment. The wettability of the modified surfaces of PET was determined by measuring the contact angle between water droplets and the modified surfaces. The modified surfaces were also characterized by AFM (atomic force microscopy) and XPS (X-ray photoelectron spectroscopy) for changes in the surface morphology, and the chemical composition and molecular structure, respectively. The contact angle decreased from 70° for unmodified surfaces to 45° for modified surface with ID = 10¹⁴ isc without O₂ and remained relatively constant with higher ID. The contact angle, however, reached a minimum value of 8° for modified surfaces with ID = 10¹⁶ isc with O₂. The improved wettability may be due to a combination of the formation of hydrophilic groups, chemical and molecular structural changes, physical structural or morphological changes, and increased roughness of the surface. The wettability of the modified surfaces also depended on the time of exposure to air. The wettability worsened with exposure time to air, but was revived by immersing the films into water. Possible mechanisms for the change of the wettability of the modified surfaces are given.

Plasma treatment of polyimide surfaces not only causes structural modification during the plasma exposure, but also leaves active sites on the surfaces that are subject to post-reaction. In this work, the effects of atmospheric fluorine plasma treatment on the surface properties and dielectric properties of polyimide thin film were investigated by using X-ray photoelectron spectroscopy (XPS), Fourier transform-IR (FT-IR) spectroscopy, and contact angle measurement. The results indicated that plasma treatment successfully introduced fluorine functional groups on the polyimide surfaces. The polyimides also exhibited good thermal stability and a lower dielectric constant. It appears that the replacement of fluorine led to the decrease of the local electronic polarizability of polyimide. Consequently, it was found that the atmospheric fluorine plasma-treated polyimides possessed lower dielectric characteristics than the untreated polyimides.

In this work, the effect of corona discharge treatment on surface properties of polyimide film was investigated in terms of FT-IR(Fourier Transform-IR), XPS(X-ray Photoelectron Spectroscopy) and contact angles. And the adhesion characteristics of the film were studied in peel strengths of polyimide coatings. As a result, polyimide surfaces treated by corona discharge led to an increase of oxygen-containing functional groups or polar component of the surface free energy, resulting in improving the adhesion characteristics of the polyimide/copper foil. However, the surface energy of the film was decreased as the aging time increased. These results could be discussed in the formation of surface functional groups or deterioration of reactive sites of polyimde film in the presence of corona treatment with aging time.

In this work, the effect of atmospheric-pressure plasma treatments on surface properties of polyimide film are investigated in terms of X-ray photoelectron spectroscopy (XPS), contact angles, and atomic force microscopy (AFM). The adhesion characteristics of the film are also studied in the peel strengths of polyimide/copper film. As experimental results, the polyimide surfaces treated by plasma lead to an increase of oxygen-containing functional groups or the polar component of the surface free energy, resulting in improving the adhesion characteristics of the polyimide/copper foil. Also, the roughness of the film surfaces, confirmed by AFM observation, is largely increased. These results can be explained by the fact that the atmospheric-pressure plasma treatment of polyimide surface yields several oxygen complexes in hydrophobic surfaces, which can play an important role in increasing the surface polarity, wettability, and the adhesion characteristics of the polyimide/copper system.

The effect of corona discharge on low-density polyethylene (LDPE) film was studied in terms of surface functionality and surface energetics of the film surfaces, improving the dyeability. The introduction of a polar group (OCO, CO, and CO) to a corona-treated LDPE film with acrylic acid could be confirmed by ESCA. The Owens–Wendt and Wu models using geometric means were studied to analyze the surface free energy of corona-treated film. It was found that the corona-treated LDPE film did lead to an increase in surface free energy, mainly due to the increase of its specific (or polar) component as the corona discharge power increased. Also, the K/S values were increased as the concentrations of dye increased. From the acid–base interaction point of view, it was found that the graft polymerization of acrylic acid onto the corona-treated LDPE film plays an important role in growing the acidic character which is one of the specific components of surface free energy, resulting in improving the dyeability with basic dyeing agent. A direct linear relationship is shown between the O_1s/C_1s ratio and the resulting K/S value or the specific component for this work.

Tetrafluoroethylene–hexafluoropropylene (FEP) copolymer sheets were modified by remote H₂, N₂, O₂, and Ar plasmas, and the effects of the modification on adhesion between FEP sheets and copper metal were investigated. The four plasmas were able to modify the FEP surfaces' hydrophilicity. Defluorination and oxidation reactions on the FEP surfaces occurred with exposure to the plasma. The hydrophilic modification by H₂ plasma was best, followed by modification by O₂, Ar, and N₂ plasmas. The surface modification of FEP by all four remote plasmas was effective in improving adhesion with copper metal. The peel strength order of the FEP/Cu adhesive joints was H₂ plasma > Ar plasma > N₂ plasma > O₂ plasma. Mild surface modification is important for the adhesion improvement of FEP with Cu metal. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1258–1267, 2002
https://onlinelibrary.wiley.com/doi/10.1002/app.2293

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.

Piezoelectric and nonpiezoelectric films of polyvinylidene fluoride (PVDF) have been treated in a microwave nitrogen and hydrogen plasma. Plasma parameters, eg ratio between N2 and H2, plasma power, gas flow rate, and the distance between the sample and the plasma have been varied in order to establish the treatment parameters that constitute a good compromise between an optimum functionalization and a minimum degradation. Under this treatment, the surface properties of PVDF have been modified in a controlled manner, allowing its metallization, necessary in a wide range of applications, without significantly changing its bulk properties.

A study of the durability of corona discharge plasma effects on a polymer surface was investigated in this work. We used the corona discharge plasma technique to modify the wettability properties of low density polyethylene (LDPE) film and evaluated the influence of relative humidity and temperature on the aging process with three different storage conditions. The effects of the aging process on the plasma-treated surface of LDPE film were quantified by contact angle measurements, Fourier-transformed infrared spectroscopy, and X-ray photoelectron spectroscopy. The results obtained with these techniques have allowed us to determine how the aging process promotes changes in the plasma-treated surface by decreasing its wettability and taking place a remarkable hydrophobic recovery process.

Surface modification by corona discharge plasma is one of the most interesting industrial applications for surface modification compared with other techniques which require vacuum conditions. In this work, we have used the corona discharge plasma technique to modify the wettability properties of low density polyethylene (LDPE) film. The effects of this treatment on the surface of LDPE film have been quantified by contact angle measurements, Fourier-transform Infrared Spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. With these methods, we have determined how the treatment modifies, activates and functionalizes the surface of LDPE film, increasing its hydrophilic behavior, and how the process parameters influence the uniformity and homogeneity of the treated surface. The results obtained show good treatment homogeneity and an improvement of adhesion properties by the functionalization and etching of the film surface.

This chapter presents after a short reminder of thermodynamic definitions, the most commonly used techniques for surface tension measurements with some details of the most interesting of them for high temperature applications. Some recent results on the evaluation of the influence of external factors, like the surrounding atmosphere, on the determination of the surface tension of molten systems are also presented. ASTRA is an experimental methodology and an integrated software to get and process data of drop shape profiles to determine surface and interfacial tension and contact-angle values. Due to its high performances in terms of time of acquisition and reliability, it is particularly suitable for both static and dynamic measurements. Indeed, by using ASTRA it is possible to reach up to two interfacial tension measurements per second, having access to dynamic measurements over very large time scale. ASTRA is currently used both for liquid metals and for liquid systems at room temperature.

In this investigation, the surface modification of poly vinylidene fluoride (PVDF) and poly methyl methacrylate (PMMA) film induced by air plasma has been investigated using contact angle measurement, electron spectroscopy for chemical analysis (ESCA), and ATR-FTIR spectroscopy. Plasma treatment affects the polymer surfaces to an extent of several hundreds to several thousand angstroms deep, and the bulk properties of the polymer substrate are never modified because of its low penetration range. Plasma surface treatment also offers the advantage of greater chemical flexibility. The plasma exposure leads to weight loss and changes in the chemical composition of the polymer film surfaces. The contact angle of water shows decrease in surface wettability of PVDF and PMMA as the treatment time increases. The improvement in adhesion was studied by measuring T-peel strength. In addition, printability of plasma treated PVDF and PMMA was studied by cross test method. It was found that printability increases considerably for plasma treatment of short duration. Surface energy and surface roughness can be directly correlated to the improvement in the aforementioned surface related properties. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Polystyrene and polyethyleneterephthalate surfaces were exposed to helium, oxygen/helium and nitrogen/hydrogen plasmas singly and in combination. The treated surfaces were evaluated by water contact-angle measurements and by x-ray photoelectron spectroscopy. It was found that the oxygen and nitrogen tend to graft to common carbon atoms, to form amide groups. The water wettability was found to correlate with the fraction of electronegative atoms incorporated into the surface. © 1998 John Wiley & Sons, Ltd.
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291096-9918%28199808%2926%3A9%3C674%3A%3AAID-SIA414%3E3.0.CO%3B2-5

A new plasma-based micropatterning technique, here referred to as plasma printing, combines the well known advantages given by the nonequilibrium character of a dielectric barrier discharge (DBD) and its operation inside small gas volumes with dimension between tens and hundreds of micrometres. The discharge is run at atmospheric pressure and can be easily implemented for patterned surface treatment with applications in biotechnology and microtechnology. In this work the local modification of dielectric substrates, e.g. polymeric films, is addressed with respect to coating and chemical functionalisation, immobilisation of biomolecules and area-selective electroless plating.

A new approach to qualitatively predicting adhesion at a solid/solid interface is described. It is based on thermodynamic compatibility of the two adhering surfaces, but it overcomes the weaknesses of existing methods by using a full set of contact angle data and by assembling the data to reveal the main features of the set without loss of information. Adhesive performance data to support this approach are presented.

The surface energy of a polymer can be increased by compression moulding against a metal substrate. After removal of the substrate relaxation to the equilibrium value sets in. We determined the rate of polymer surface energy relaxation as a function of temperature. For a vinyl chloride-vinyl acetate copolymer we determined an activation energy of the relaxation process that could be correlated to segmental motions in this polymer. For a plasticized polyvinylchloride we found a lower activation energy and a larger rate of relaxation, which is the result of the action of plasticizers on segmental motions. In the case of polyethylene the results indicate segmental motions in amorphous regions in the polymer. With polyethylene the activation energy drops when nearing the melt temperature. The movements of molecular segments correspond to a desorption process at the polymer surface, after removal of the substrate. This agrees with the adsorption during compression moulding, as repotted in earlier work.

Radio frequency plasma treatment of polydimethylsiloxane (PDMS) is a useful way of increasing wettability to improve adhesion. Its main defect is the subsequent rapid recovery of hydrophobicity. The fluorosilicone polymethyltrifluoropropylsiloxane (PMTFPS) is another low surface energy silicone where improved wettability is often desired. We have directly compared the behavior of PMTFPS and PDMS using air, oxygen, helium and argon plasma gases. The effect of the plasma has been investigated by water contact angle changes and by x-ray photoelectron spectroscopy (XPS) surface characterization. Both an unfilled PMTFPS gum and a filled elastomer were examined. PMTFPS is affected in much the same way as PDMS, an oxidized silica-like surface region is produced. This is shown by the shift in the high resolution Si 2p spectra to higher binding energy which is most marked in the case of helium treatment. Significant improvements in water wettability occur with helium treatment having the greatest effect but the hydrophobic recovery is mostly complete within 24 hours in all cases. Multiple treatments followed by water storage are effective in maintaining wettability for at least a week.

Contact angles of water, glycerol, formamide, ethylene glycol, 1-bromonaphthalene, and bromobenzene were measured in the temperature range 5–160° on surfaces of polyethylene, polystyrene, polyacetal, polycarbonate, poly(ethylene terephthalate), and poly(tetrafluoroethylene-co-hexafluoropropylene). Stable advancing and receding angles were found and these varied linearly with temperature except in the range where solubility or swelling was evidence. Superheated water wet all the polymers to a greater degree than predicted. For the fluoropolymer all the liquids showed a negative temperature coefficient of the contact angle, both advancing and receding, ranging from 0.03 to 0.1 deg/°C. For the other polymers coefficients for advancing angles were nearly all negative and ranged from 0.03 to 0.18 but most receding angle values were positive; several liquid-polymer pairs showed a negligible coefficient. Temperature coefficients of the critical surface tension and of the dispersion surface tension of each solid were evaluated. Correlations of these derived quantities are discussed.