Poly(ethylene terephthalate) (PET) film surfaces were modified by argon (Ar), oxygen (O₂), hydrogen (H₂), nitrogen (N₂), and ammonia (NH₃) plasmas, and the plasma-modified PET surfaces were investigated with scanning probe microscopy, contact-angle measurements, and X-ray photoelectron spectroscopy to characterize the surfaces. The exposure of the PET film surfaces to the plasmas led to the etching process on the surfaces and to changes in the topography of the surfaces. The etching rate and surface roughness were closely related to what kind of plasma was used and how high the radio frequency (RF) power was that was input into the plasmas. The etching rate was in the order of O₂ plasma > H₂ plasma > N₂ plasma > Ar plasma > NH₃ plasma, and the surface roughness was in the order of NH₃ plasma > N₂ plasma > H₂ plasma > Ar plasma > O₂ plasma. Heavy etching reactions did not always lead to large increases in the surface roughness. The plasmas also led to changes in the surface properties of the PET surfaces from hydrophobic to hydrophilic; and the contact angle of water on the surfaces decreased. Modification reactions occurring on the PET surfaces depended on what plasma had been used for the modification. The O₂, Ar, H₂, and N₂ plasmas modified mainly CH₂ or phenyl rings rather than ester groups in the PET polymer chains to form CO groups. On the other hand, the NH₃ plasma modified ester groups to form CO groups. Aging effects of the plasma-modified PET film surfaces continued as long as 15 days after the modification was finished. The aging effects were related to the movement of CO groups in ester residues toward the topmost layer and to the movement of CO groups away from the topmost layer. Such movement of the CO groups could occur within at least 3 nm from the surface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3727–3740, 2004
https://onlinelibrary.wiley.com/doi/abs/10.1002/polb.20234

Surface modification of poly(lactic acid) (PLA) film surface by Ar-plasma was investigated by contact angle measurements and XPS in order to answer the following two questions. (1) Could the Ar-plasma modify the PLA film surfaces? (2) What chemical reactions occurred on the film surfaces during the Ar-plasma treatment? The Ar-plasma treatment did not lead to hydrophilic modification of the PLA film surface, but to degradation reactions of the PLA film. Poor modification may be due to instability of the carbon radicals formed from CO bond scission in the PLA chains by the Ar-plasma.

A new surface modification technique for PET films is proposed. This technique, called VPI modification technique, is a combination of two processes: The first step involves the deposition of vinylphthalimide (VPI) on the PET film surfaces, followed by Ar plasma irradiation of the VPI-covered film surfaces. The VPI modification technique led to large increases in the N/C atom ratio on the PET film surfaces. On the VPI-modified PET film surface, a new N_ls peak containing two components due to amide groups as well as imide groups appeared. The C_ls signal for the VPI-modified PET film surface also showed a new component due to ketone groups. These changes indicate that VPI reacted with the PET film surfaces to form nitrogen-containing groups. VPI modification made PET film surfaces hydrophilic. The VPI-modified film surfaces showed a decrease in water contact angle from 73 degrees to 48–56 degrees.

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.

ETFE film surfaces were modified by CO₂, O₂ and Ar plasmas in order to form carboxylic groups on their surfaces, and the possibility that carboxylic groups could be predominantly introduced into the CH₂–CH₂ component rather than the CF₂–CF₂ component in the ETFE polymer chains was investigated from the viewpoint of chemical composition analyzed by XPS. The CO₂ plasma modification was more effective in the selectivity of the CH₂CH₂ component for the introduction of carboxylic groups, as well as in the concentration of the carboxylic groups formed on the film surfaces than O₂ plasma modification. The concentration of carboxylic groups formed on the ETFE film surfaces by the CO₂ plasma modification was 1.40–1.50 groups per 100 carbons. Topographical changes on the ETFE film surfaces by the plasma modification were also investigated by scanning probe microscopy.

The surface modification of polyethylene surfaces by NO-plasma irradiation was investigated from the point of view of the hydrophilicity and chemical composition. The hydrophilicity was evaluated from the advancing contact angle of water and the surface energy. The chemical composition of the modified surfaces was determined by diffuse reflectance Fourier transform infrared spectroscopy and XPS. NO-plasma irradiation for 5 min made the polyethylene surfaces hydrophilic. The advancing contact angle of water on the modified polyethylene surfaces reached 28 deg, and the surface energy was 57.6 mJ/m². The incorporation of oxygen and nitrogen moieties on the polyethylene surfaces occurred during the NO-plasma irradiation. The main oxygen moieties were carbonyl groups, hydroxyl groups, and ether linkages; the nitrogen moieties were amino groups. NO-plasma irradiation was more effective in improving the hydrophilicity than the O₂ plasma, N₂ plasma, or corona discharge treatment.

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
https://onlinelibrary.wiley.com/doi/abs/10.1002/app.10865

Surface modification of poly(tetrafluor oethylene) (PTFE) by NH₃-plasma treatment was investigated by means of contact angle measurement, XPS, and ATR FT/IR spectroscopy. The modified surfaces were adhesively bonded to nitril rubber. The NH₃-plasma irradiation made PTFE surfaces hydrophilic. The contact angle of water on the modified PTFE surface was 16 deg, and the surface energy was 62-63 mJ/m². The NH₃-plasma irradiation improved adhesion between PTFE and nitril rubber using a phenol-type adhesive. The peel strength of the joints reached 8.1 × 10³ N/m. Carbonyl and amido groups were created on PTFE surfaces by the NH₃-plasma irradiation. The mechanism of the improvement of adhesion by the NH₃-plasma irradiation is discussed.

To improve the adhesion between poly(p-phenylene terephthalamide), PPTA, fiber and silicone rubber, the surface modification of PPTA was investigated. Combining plasma treatment and coupling agent treatment with the silicone adhesive was found to be effective in improving adhesion. The combination process made the pull-out force of the PPTA yarn/silicone rubber composite 2.5 times higher, compared with the plasma treatment or the coupling agent treatment alone. The plasma treatment led to the elimination of carbonized layer from the PPTA yarn surface and the formation of oxygen functionalities including CO and CO groups. The elimination of the carbonaceous deposits from the PPTA surface and the interaction between the silicone adhesive and the oxygen functionalities created by the plasma treatment contribute to the improvement of adhesion with silicone rubber.

Kapton films were treated with seven plasmas: Ar-, N₂-, O₂-, CO-, CO₂-, NO-, and NO₂- plasmas. Surface properties and chemical composition of the plasma-treated Kapton films were investigated from the contact angle measurement, and the IR and XPS spectra. The plasmas, especially NO- and NO₂-plasma, made the Kapton film surface hydrophilic. The XPS and IR spectra showed that the plasma led to the modification of the imide groups in the Kapton film to secondary amide and carboxylate groups.

Surface modification of poly(ethylene terephthalate) (PET) film by an argon (Ar) plasma was investigated as a function of the distance from the Ar plasma zone. Changes in distance between the PET film and the Ar plasma zone had a strong influence on the surface modification of the film. The direct Ar plasma treatment (distance between the PET film and Ar plasma zone = 0 cm) was effective in hydrophilic surface modification, but heavy etching reactions occurred during the modification. On the other hand, the remote Ar plasma treatment (distance between the PET film and Ar plasma zone = 80 cm) modified the PET film surfaces to be hydrophilic without heavy etching reactions, although the hydrophilicity of the PET was lower than that by the direct Ar plasma. The remote Ar plasma treatment was distinguished from the direct Ar plasma treatment from the viewpoint of degradation reactions. The remote Ar plasma treatment rather than the direct Ar plasma treatment was an adequate procedure for surface modification and caused less polymer degradation on the film surface. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 808–815, 2001
https://onlinelibrary.wiley.com/doi/10.1002/1097-4628(20010131)79:5%3C808::AID-APP50%3E3.0.CO;2-B

FEP sheets were modified with a remote hydrogen plasma and the effects of the modification on the adhesion between copper metal and FEP sheets were investigated. The remote hydrogen plasma treatment is able to make FEP surfaces hydrophilic. In the remote hydrogen plasma treatment process, both defluorination and oxidation occur on the FEP surface. The oxidation reactions on the FEP surface form oxygen functional groups such as CO and CO groups. Modification of the FEP surface by the remote hydrogen plasma is effective in improving the adhesion of copper metal. The peel strength of the Cu/FEP system increased form 0 to 195 mN/5 mm, and the failure mode changed from the Cu metal/FEP polymer interface to within the FEP polymer layer. Remote hydrogen plasma treatment may be a preferable pretreatment of the FEP surface for adhesion with copper metal.

To draw a relationship between surface concentration of the siloxane segment and adhesion performance, surface properties of the polydimethylsiloxane—poly(methyl methacrylate) block copolymers(PDMS-b-PMMA) prepared via poly(azo-containing siloxaneamide)s and their PMMA blends have been studied by measurements of FT-IR spectra, water contact angle, ESCA spectra and 180° peel strength toward pressure-sensitive adhesive tape. The water contact angles of the chloroform-cast blend films increased abruptly with siloxane bulk concentrations, or siloxane contents, particularly, on the air-side surfaces to reach almost 100° in low siloxane content. A marked increase of the contact angle was observed in the blends containing siloxane chain length (SCL) of longer than 2000. ESCA data evidently confirmed for these blend systems that the siloxane segments with low surface energy were accumulated or enriched mainly on the air-side surface, and that, on the other hand, polar PMMA segments with high surface energy were oriented to the glass-side surface and the inside of the films. This surface accumulation behavior of the siloxane segments reflected the 180° peel strength, as a measure of adhesion performance. The water contact angle and 180° peel strength were unequivocally correlated to the siloxane surface concentration estimated from ESCA data. Conversely, in the compression-molded blend films made by a hydraulic press between a Teflon and a stainless steel plate, the extent of surface accumulation of the PDMS segment was lower than that of the chloroform-cast films, suggesting lower degree of segment migration in hot-press films, probably due to substrate surface energy and lower relaxation in the blend melts.

A simple model for advancing dynamic menisci of the interface between two immiscible fluids is proposed on the hypothesis that there is a monomolecular film which precedes an apparent contact line and that a frictional force due to the solid surface is balanced with the interfacial tension forces on the film. An analytical solution for dynamic contact angles on vertical and inclined solid surfaces of plates is obtained as a function of the interfacial capillary number, the static contact angle, and the parameters of Langumuir's duplex film model. An analytical solution for dynamic meniscus heights is also derived. The analytical solutions are compared with previous experimental data. The agreement between the theoretical and experimental results is found to be fairly good, average deviations being 3.8 and 12%, respectively, for dynamic contact angles and dynamic meniscus heights at the solid surface.

Recent advances in surface science have led to a broad interest in wetting and/or spreading characterization of solid surfaces. Wettability of a solid surface can be defined as the tendency of a liquid to spread over the surface which is measured in terms of an angle, ie, contact angle between the tangent drawn at the triple point between the two phases (liquid and vapor) and the substrate surface. Reproducible and accurate measurements of the contact angle from the experiments are crucial in order to analyze the spreading behavior of a substrate. Spreading is greatly affected by different factors including liquid properties, substrate properties, and system/operating conditions. Here, different types of spreading phenomena in terms of drop evaporation on reactive/non-reactive surfaces and correct measures to obtain accurate contact angles in such scenarios are presented.

Oxygen mixed with nitrogen trifluoride (NF3) was used as the gas source for the plasma etching to increase the etching rate of the polyimide (PI) film. In order to investigate the effects of NF3 addition, surfaces of the etched PI films were analyzed with various methods. From the results of x-ray photoelectron spectroscopy (XPS), the chemical bonding state of the etched PI surface with 30% NF3/70% 02 plasma was similar to that of the surface prepared using 100% 02 plasma. The results of FT-IR analyses showed that a part of materials deposited on the etched PI film was soluble in chloroform and it contained carbonyl and ether compounds. Furthermore, the etching products were analyzed using quadrupole mass spectrometry (QMS) and gas chromatography. The main products were found to be H20, HF, CO and C02. In addition, CO/C02 ratio was found to be related to the etching rate which depended on the NF3 concentration.

Oxidation of a polyethylene (PE) surface by corona discharge and the subsequent graft polymerization of acrylamide (AAm) were studied. The maximum amount of peroxides introduced by corona treatment at a voltage of 15 kV was about 2.3 × 10⁻⁹ mol cm⁻². The decomposition rate of peroxide and the dependence of graft amount on the storage period of the corona-treated PE films showed that there were several kinds of peroxides, the labile one being mainly responsible for the initiation of graft polymerization. When the corona-treated film was brought into contact with a deaerated aqueous solution of AAm, graft polymerization took place more strongly with the treatment time, but was reduced after passing a maximum. Although the x-ray photoelectron spectroscopic analyses of the corona-treated PE films showed homogeneous oxidation of the outer polymer surface by corona discharge, optical microscopy on the cross section of the grafted film revealed the graft polymerization to be limited to a very thin surface region.

A diblock copolymer of deuterated styrene and isoprene (dPS−PI) with a small volume fraction of isoprene was chemically modified to incorporate pendant fluorinated side chains (“fingers”). The composition distribution of the diblock copolymers within a high molecular weight polystyrene (PS) homopolymer was determined by forward recoil spectrometry. Surface segregation and interfacial segregation of the modified block copolymers from a polystyrene matrix are observed in as-spun films. Equilibrium segregation was achieved on annealing at 160 °C for several days. The segregation isotherms at the air−polymer interface are shown to be quantitatively described by a self-consistent mean field theory (SCMF), and these permit us to estimate an effective Flory parameter which describes the attraction of the fluorinated segments to the surface and their repulsion from the bulk. The change in the surface tension as a result of the adsorption of the block copolymers at the air−homopolymer interface was evaluated from the predictions of SCMF theory and compared with the changes in the water contact angle observed. Advancing water contact angle data are consistent with the presence of a nonuniform layer of PS, CF₂, and CF₃ segments on the surface of the segregated samples.

For substrates such as polyesters having limited capacity for hydrogen bonding or other specific interactions, thermodynamic compatibility of the substrate and adhesive is shown to be a key factor in promoting bondability to the substrate. Such compatibility occurs, as shown by Abere, when the cohesive energy densities (CED) or solubility parameters (δ = √CED) of substrate and adhesive are matched. Investigations with polyester film-adhesive-film model systems with the use of a variety of nonpolar (hydrocarbon) and polar (chlorinated compounds, ethers, esters) adhesives illustrate how compatibility promotes bondability to poly(ethylene terephthalate). The poor adhesion of polyester fibers to resorcinol–formaldehyde–latex (RFL) adhesives is attributed to the incompatibility of resorcinol (δ = 16.0) with the polyester (δ = 10.3). Adhesion to RFL was improved by substituting the more compatible n-hexyl resorcinol (δ = 12.5) for resorcinol in RFL adhesives. Currently, the best adhesive systems for polyester tire yarns are those (e.g., isocyanate–epoxy) involving formation of urethane polymers having matching δ values with poly(ethylene terephthalate).

The influence of release agents, impurities and light stabilizers on the mechanisms of pretreatment operations, such as flame or plasma treatment, of thermoplastic materials used in the automotive industry has been investigated by X-ray photoelectron spectroscopy (XPS), zeta potential and contact angle measurements. It is shown that the presence of release agents on thermoplastic polyurethane can be detected by contact angle and zeta potential measurements. Sterically hindered amines (HALS) used as light stabilizers in polypropylene-ethylene-propylene-dienemonomer rubber blends (PP-EPDM) enhance the result of flame treatment whereas the effect of oxygen plasma treatment is not changed by the presence of HALS products.

The possibility of characterizing dispersion forces and acid-base interactions by means of physico-chemical measurements is demonstrated by the examples of contact angle and zeta potential measurements, with special attention being given to the latter. This method has been applied, to characterize the effect of plasma and flame treatment on the adhesion behaviour of injection moulded poly(propylene) specimens. The results with respect to acidic or basic functional surface sites, as obtained by zeta potential measurements, correlate with the elemental surface compositions determined by XPS. There is no general interrelation between acidic and basic parameters determined by contact angle measurements and the results of zeta potential and XPS measurements.

In this work, the effect of medium pressure plasma treatment on thin poly-ϵ-caprolactone (PCL) layers on glass plates is investigated. PCL is a biocompatible and biodegradable polymer which potentially can be used for bone repair, tissue engineering and other biomedical applications. However, cell adhesion and proliferation are inadequate due to its low surface energy and a surface modification is required in most applications. To enhance the surface properties of thin PCL layers spin coated on glass plates, a dielectric barrier discharge (DBD) at medium pressure operating in different atmospheres (dry air, argon, helium) was used. After plasma treatment, water contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to examine the PCL samples. These measurements show that the medium pressure plasma treatment is able to increase the hydrophilic character of the samples, due to an incorporation of oxygen groups at the surface and that the surface roughness is significantly decreased after plasma treatment.

In this paper, a dielectric barrier discharge (DBD) operated at (sub)atmospheric pressure in a 95/5% He/CF₄ mixture is employed to increase the hydrophobicity of a poly(ethylene terephthalate) (PET) film. This paper studies the influence of different operating parameters on the hydrophobic properties of the PET film using contact angle measurements. Results clearly show that the hydrophobicity of the PET film is only enhanced when using large gas flows. Moreover, this work demonstrates that operating pressure and discharge power have a significant influence on the rate of plasma modification as well as on the uniformity of the plasma treatment. Also important to mention is that no ageing effect is observed. As a result, one can conclude that the utilized DBD is an efficient tool to create stable, hydrophobic PET surfaces.

During the past decade polylactide acid (PLA) polymer has been the subject of numerous researches aimed at comparing it with traditional petroleum based polymers for many packaging applications. PLA is biodegradable and derived from agricultural by-products such as corn starch or other starch-rich substances like maize, sugar or wheat.While PLA is currently being used in many packaging applications with well documented performance, little work has been done comparing printing processes and performance. This study presents PLA printing performance and sustainability findings using the common flexography printing process. Various analytical methods were used to evaluate performance and provide recommendations for optimized printing on PLA as compared to PET, oriented PP and oriented PS. Results of this study found that PLA films were comparable in printability and runnability to standard petroleum based flexible packaging films.

In order to explore the fundamental mechanism of paint adhesion to polymer substrates the surface of polypropylene- ethylene propylene rubber (PP-EPR) blends was modified by flame or plasma treatments. The changes in surface composition and properties were investigated and discussed in light of the results of simple adhesion tests. The topography and surface properties of the PP-EPR samples were studied by employing various surface sensitive techniques. Additionally, the surface properties of the pre-treated PP-EPR were compared with the model polymers poly(methyl methacrylate) (PMMA) and polycarbonate (PC) displaying a poor and an excellent paint adhesion, respectively. Differential scanning calorimetry (DSC) measurements showed that the miscibility of the polymer substrate with paint components was an essential factor for the understanding of the adhesion mechanism. A general model of paint adhesion to polymer surfaces is proposed, where the degree of interdiffusion of the polymer chains of the substrate and paint in the interphase determines the adhesion strength.

The effect of a cold remote N₂ plasma (CRNP) or N₂ + O₂ plasma (CRNOP) on poly(ether ether ketone) (PEEK) is studied. The amount of nitrogen or oxygen uptake and functionalities are determined by x-ray photoelectron spectroscopy (XPS). After CRNP treatment, the N/C and O/C atomic ratios are 0.301 and 0.333, respectively. Nitrogen functional groups are not detected by CRNOP treatment, and the O/C atomic ratio is then 0.785. The ageing process of the treated PEEK surface in the open air is investigated in both cases. For CRNOP treatment the O/C atomic ratio decreases by carbonate function departure, whereas for CRNP treatment the total amount of nitrogen and oxygen graft atoms goes through a maximum after 1 h of air exposure.

A starch-based biodegradable (BD) low density polyethylene (LDPE) film can be directly printable without any corona treatment, unlike virgin LDPE film. Such a film shows poor adhesion and nail scratch resistance of the ink on the printed area of the film. In order to increase the adhesion and nail scratch resistance of the ink on the printed BD film, grafting of acrylonitrile onto the BD film is carried out. The polyacrylonitrile grafted BD film shows better adhesion, nail scratch resistance, and printability. The printability of the polyacrylonitrile grafted BD film is comparable to the conventional corona treated LDPE film. The extent of printability is a function of the surface smoothness, as well as the optimum percentage of grafting on the biodegradable film. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1273–1277, 2001
https://onlinelibrary.wiley.com/doi/abs/10.1002/1097-4628(20010214)79:7%3C1273::AID-APP150%3E3.0.CO;2-L