A remote atmospheric pressure discharge working with ambient air is used for the near room temperature treatment of polymer foils and textiles of varying thickness. The envisaged plasma effect is an increase in the surface energy of the treated material, leading, e.g., to a better wettability or adhesion. Changes in wettability are examined by measuring the contact angle or the liquid absorptive capacity. Two regimes of the remote atmospheric pressure discharge are investigated: the glow regime and the streamer regime. These regimes differ mainly in power density and in the details of the electrode design. The results show that this kind of discharge makes up a convenient non-thermal plasma source to be integrated into a treatment installation working at atmospheric pressure.

Polyethylene (PE) is often used in several industrial applications including the building, packaging and transport industries. Aluminum (Al) is widely used in different applications in the automotive, railway, aeronautic, and naval industries because of its excellent mechanical and chemical properties. Laminates prepared from Al and PE lead to an enhancement in physical and mechanical properties. These materials play a main role in the packaging and building sectors, such as in TetraPak containers and aluminum composite panels. The main problem observed is associated with the adhesion between polymers and metals. This research focused on investigating the enhancement in the adhesion of the PE/Al laminate using the corona discharge. The corona treatment of the surfaces led to a significant increase in the adhesion of the PE/Al laminate as a result of improved surface properties confirmed by peel test measurements. Moreover, the positive effect of the corona treatment in combination with a primer on the improvement of adhesion characteristics was observed too. Different analytical techniques were employed to characterize the effect of the corona treatment on the improvement in adhesion of PE/Al. A significant increase in wettability was confirmed by the measurement of contact angles. Changes in the surface morphology of the PE and Al surface, after the corona treatments at different operating conditions, were observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). In addition, x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to analyze changes in chemical composition after the corona discharge effect on PE and Al surfaces.

The aim of this publication is to describe an industrial application of the oxyfluorination process to polymer webs. Controlled oxyfluorination of polymer surfaces is a solventless, highly efficient and cost-effective technique of surface modification. The adhesive properties of oxyfluorinated polypropylene films are largely improved so that a variety of solventand water-based printing inks used in contact printing technology can be used. We have confirmed that, in many cases, the necessity to employ an expensive top-coating process that uses acrylic primers to optimise the film printability, can be avoided. The oxyfluorination process with its long lasting effect is a competitive alternative to the simple corona discharge treatment. The oxyfluorination ALKOR' SURFOX process can be described as an environmentally responsible technology that delivers a broad range of products possessing many exceptional surface properties.

A summary of recent studies on the corona treatment of films is presented. Chemical functional groups generated by the corona discharge on these films are identified and their effect on ink film wettability and adhesion discussed.

It is well known that in extrusion coating, the coating adhesion to the substrate decreases with decreasing thickness. The study on this phenomenon is divided into three parts. Part I explores the reduction in adhesion of LDPE to paper and other porous substrates. Several hypotheses are proposed for the origin of this decrease, including a reduction in oxidation time, faster cooling in the air gap, and more rapid quenching in the nip. A model of the molten polymer penetration into the substrate shows that the greatest effect is cooling in the nip; thinner coatings have less time to flow into the substrate interstices once the chill roll contact is made. The model results agree well with experimental adhesion data from the literature.

In Part II, adhesion to aluminum foil and other nonporous substrates is studied. Several hypotheses are proposed for why peel strength decreases in these structures, including a reduction in the air gap time, faster air gap cooling, more rapid nip quenching, and stress imposed during drawing. Modeling and experimental results show that cooling in the nip and imposed stress have the greatest impact.

In Part III, the peel test is analyzed to understand why the peel strength of better adhering adhesives are more sensitive to changes in coating thickness. The analysis shows that changes in the critical dimension of the deformation region at the peel front may be responsible.

This study describes experiments to quantify polymer surface energy changes after exposure to atmospheric plasma. Atmospheric plasma treatment permits surface functionalization at near-ambient temperatures. Polyethylene and polystyrene are treated with an atmospheric plasma unit. The increased surface energy and improved wetting characteristics lead to a significant adhesion improvement with adhesives that cannot be used without surface treatment.

Polyamide 6, polyamide 12, polybutyleneterephthalate, and polyetherimide films are plasma treated in an APGD unit using various applied voltages, gas flow rates, frequencies, and dwell times. The results show changes in the surface chemistry (FTIR); the degree of change in dynamic contact angle is found to be dependent on the polymer type, dwell time, and electrical characteristics of the plasma.

Glycerol monostearate (GMS) can serve as an anti-fogging agent by increasing the hydrophilic nature of a film surface. In this study, blends of GMS and LLDPE were extruded into film and the GMS was allowed to migrate to the surface over time. The surface was characterized by measuring the static water contact angle, which was then used to calculate the surface free energy of the film. Results showed that the equilibrium wettability of the film deviated dramatically from that of neat LLDPE when the GMS concentrations were greater than about 1900 ppm. Time-dependent studies demonstrated that the rate of surface-energy change was significantly influenced by the GMS concentration.

Polyolefin plastomer films formulated with slip and antiblock were blown on a wide die gap with and without two Dynamar^™ polymer processing additives (PPAs). A wide die gap was used so that melt fracture-free film could be obtained with no PPA present for comparison purposes. The films were analyzed for the following properties: surface tension (on treated films), gloss, haze, clarity, transmittance, hot tack, heat seal, COF and block. In addition, the surface of films was examined using ESCA (Electron Spectroscopy for Chemical Analysis) and SSIMS (Static Secondary Ion Mass Spectrometry) to determine the surface chemical composition. PPAs when used at typical dose levels were shown to have essentially no effect on the surface and optical properties of plastomer films.

With increasingly stringent EPA guidelines for controlling emissions of volatile organic compounds on the horizon, the desirability to move to water-based printing inks is evident This paper examines the effects of corona discharge treat ments which are commonly used to improve ink adhesion to polvethylene. Electron spectroscopy for chemical analysis (ESCA) was used to determine the surface chemi cal changes induced by corona treatments in pure polyethylene extruded films and in formulated resin systems This data was correlated with surface tension and ink adhesion measurements to show the effects of treatment and additives on the final printability of the films with particular emphasis on water-based inks. In addition, the effects of stonng treated film prior to printing and of retreating these films were also examined The results of these tests have shown that formulated linear low den sity polyethylene (LLDPE) films treat and print at least as easily as high-pressure low-density polyethylene (HP-LDPE) counterparts.

Metallized OPP (oriented polypropylene) film offers exceptional gas and water vapor barrier properties, making it one of the most cost-effective flexible protective packaging materials. Its barrier properties correlate with opacity, which, in turn, de pends on the degree of coverage by the metallization. Minor defects, such as scratches, will generally represent only a small percentage of the total coverage of a package and have a proportionally small effect on the barrier properties of the pack age. The high-energy metal surface is extremely active and will wet well and adhere strongly when clean. In fact, it is so active that it is easily coated with trace amounts of any low energy organic material with which it makes contact. For assurance of consistent wetting and bonding, metallized OPP surfaces should be cleaned in-line, such as by bare-roll corona treatment.

Blown film processors, large and small, have limited resources in both capital and manpower to devote to optimizing their productivity. Yet avenues of improvement are open for even the most over-extended organization. And some of the most effective modifications cost little more than a small change in equipment orientation or procedures. A key aspect of optimizing a blown film layout is line footprint and determining how to minimize footprint and maximize output with each integral piece of equipment on the line. Multiple surface treatment systems are integral to every blown film line and can control product quality and line efficiencies. The objective of this work is to present best practices of blown film manufacturers ranging from multinationals to small privately owned operations relative to the most effective surface treatment system designs, their roll coverings, optimum power density settings, alternative treatment technologies, troubleshooting protocols, and model line layouts that optimize production output.

The peel characteristics of sealed low-density polyethylene/isotactic polybutene-1 (PE-LD/iPB-1) films, with different contents of iPB-1 up to 20 m.-% (mass percentage), were evaluated and simulated in dependence on the iPB-1 content, and in dependence on the peel rate. Sealing involves close contact and localized melting of two films for a few seconds. The required force, to separate the local adhered films, is the peel force, which is influenced, among others, by the content of iPB-1. The peel force decreases exponentially with increasing iPB-1 content. Transmission electron microscopy studies reveal a favorable dispersion of the iPB-1 particles within the seal area, for iPB-1 concentrations ≥6 m.-%. Here, the iPB-1 particles form continuous belt-like structures, which lead to a stable and reproducible peel process. The investigation of the peel rate-dependency on the peel characteristics is of important interest for practical applications. The peel force increases with increasing peel rate by an exponential law. A numerical simulation of the present material system proves to be useful to comprehend the peel process, and to understand the peel behavior in further detail. Peel tests of different peel samples were simulated, using a two-dimensional finite element model, including cohesive zone elements. The established finite element model of the peel process was used to simulate the influence of the modulus of elasticity on the peel behavior. The peel force is independent of the modulus of elasticity, however, the peel initiation value increases with increasing modulus of elasticity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 https://onlinelibrary.wiley.com/doi/10.1002/app.28999

We propose an equation, based on “reciprocal” mean and force additivity, for calculating the interfacial tension between polymers or between a polymer and an ordinary liquid:

The wetting properties of a series of polyacrylates containing the fluoroalkyl group have been studied. Where n is 7 and 9, the polyacrylates are highly crystalline at room temperature. Since the polymers were prepared under atactic free-radical conditions and the polyacrylates with shorter alkyl groups (where n is 3 or 5) were not crystalline at room temperature, the crystallinity is presumed to occur as a result of side-chain packing and not involve the backbone. The polymers become more wet-table (higher γ_c) as polymer crystallinity was reduced by quenching or heating past T_m. Correlations have been made between the work of Zisman and co-workers on the wetting properties of various fluorinated acid monolayers and the wetting properties of these fluoroalkyl acrylates. The results obtained in this study concerning the influence of polymer crystallinity on surface wetting are discussed in relation to the findings of Schonhorn and Ryan on the wettability of polyethylene single crystal aggregates.

New reaction products have been generated on polyethylene and polystyrene surfaces using a novel two-step process. The first stage involves exposure to a downstream nitrogen plasma, and the second to either ozone or a corona discharge. It is observed that each of the two-step reactions yields very different reaction products, with an apparent increase in the formation of CO functional groups in the former case and the formation of surface NO₂ groups in the latter case.

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.

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.

Gas phase chemical modification (GCM) is found to be more preferable as a pretreatment for the XPS surface analysis of polymer materials than the conventional liquid phase treatment because it can circumvent problems such as solvent contamination and swelling. We have tried the quantification of the surface composition successfully by estimating the yield of the reaction from model samples. GCM was then applied to correlate the surface composition of NH₃ plasma-treated polystyrene films with their cell-affinity. The amount of primary-amine and that of carboxylic acid were directly determined by GCM. Although the amount of primary-amine, 15–20% of total nitrogen, did not depend on the treatment intensity, the total amine content for the treated samples increased with the plasma treatment intensity. The quantity of carboxylic acid generated was found to be very small. All treated samples had better cell-affinity than the control. The sample N2 (of medium treatment) showed the best cell-affinity. The most strongly treated sample N3, with larger amine content than N2, showed worse cell-affinity because of the interference by the sputtered SiO₂ on the surface.

ESCA and contact angle measurements were used to characterize the surfaces of polypropylene and glass substrates exposed to CF₄, CF₃H, CF₃Cl, and CF₃Br plasmas. The use of both organic and inorganic substrates allowed clear distinction between treatments which led to plasma polymerization and treatments which caused grafting of functional groups directly to the substrate surfaces. CF₄ plasmas were the only treatments studied which fluorinated polypropylene surfaces directly, without the deposition of a thin, plasma-polymerized film. CF₃H polymerized in a plasma, while CF₃Cl and CF₃Br plasmas caused chlorination and bromination of polypropylene surfaces, respectively. Correlations were made between the active species present in the plasmas and the surface chemistry observed on the treated polypropylene substrates.

ESCA and contact-angle measurements were used to characterize the surfaces of polystyrene films exposed to SF₆, CF₄, and C₂F₆ plasmas. SF₆ plasmas cause loss of aromaticity in the polystyrene surface region via saturation of the phenyl ring and/or carbon-bond breakage and subsequent fluorination. C₂F₆ plasmas graft CF_x radicals directly to the polystyrene surface without necessarily destroying the aromaticity of the polymer. CF₄ plasmas appear to be intermediate in character between SF₆ and C₂F₆ plasmas.

Recent work in our laboratories has fully characterized the surface region of a segmented poly(ether-urethane) (PEU) extending from the air/polymer interfacial region through bulk depths in the micron range. This characterization utilized energy and angle dependent Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR), and Comprehensive Wettability Profiling (contact angle using a homologous series of liquids) as defined by Zisman. In this study this same multi-analytical-technique approach is used to elucidate changes in these PEU surfaces induced through an H₂O Radio Frequency Glow Discharge (RFGD) plasma. This investigation reports both qualitative and quantitative changes due to the modification treatments as well as the permanency of the changes effected on these surfaces through the plasma treatment. From our analyses, the amount of surface residing polyurethane (hard segment) is observed to increase due to a proposed plasma etching mechanism. Further, the addition of oxygen containing functionality is detected at the modified surfaces unique with respect to the unmodified PEU. These surface modifications which show large increases in wettability, are finally observed to be semi-permanent over a time period of 6 months.

Surfaces of polymers [polyethylene, polystyrene, poly(ethylene terephthalate), poly(oxymethylene), cellulose acetate, polyacrylonitrile, nylon 6, and polytetrafluoroethylene] treated with argon (inert) and nitrogen (reactive) plasma were examined by ESCA (electron spectroscopy for chemical analysis). Argon plasma treatment generally introduces oxygen functionalities into the polymer surface. Nitrogen treatment generally incorporates nitrogen and oxygen functionalities into the treated surface. The extent of oxygen incorporation is typically less than that produced by argon plasma. When nitrogen and oxygen functional groups are already in a polymer structure, the extent of additional incorporation of these two elements as a result of plasma treatment is very much less than with other polymers. Polymers which contain only one of the elements tend to incorporate the other element to much the same degree as polymers without either element initially present.

Modification of polyethylene and polypropylene film and powder surfaces with oxygen and hydrogen peroxide is promoted by nonporphyrinic, nonfree radical based iron reagents such as Fe₃O(OCOCH₃)₆(C₆H₅N)_3.5 and FeCl₃ • 6H₂O/picolinic acid. These oxidation systems introduced small amounts of carbonyl groups onto the surface of these hydrocarbon polymers. The most visible manifestation of this reaction was increased polyolefin wettability toward water. IR spectroscopy, XPS spectroscopy, and chemical derivatization all were used to verify that the reaction had occurred and that a chemically derivatizable surface had been prepared. The overall process produced a fraction of the density of functional groups introduced by conventional etching chemistry.

The crosslinking of an ethylene–;tetrafluoroethylene copolymer by exposure to an argon plasma, excited by an inductively coupled RF field, is studied over a wide range of pressures and power loadings. The results are interpreted in terms of a two-component, direct and radiative energy-transfer model showing that the outermost monolayer crosslinks rapidly via direct energy transfer from argon ions and metastables.

The crosslinking of an ethylene–tetrafluoroethylene copolymer by exposure to a variety of inert gas plasmas, excited by an inductively coupled radiofrequency (RF) field, has been studied. The rates for direct and radiative energy-transfer processes are determined within the framework of a kinetic model of the system and are shown to have a strong dependence on the sustaining gas, as do the average depths of penetration of the ions and metastable species. Helium is found to be the most efficient gas for the crosslinking of the outermost few monolayers whereas the crosslinking of the subsurface and bulk polymer is best effected by neon. Madelung charge potential calculations have been performed to simulate the experimentally determined x-ray photoelectron spectroscopy (ESCA) spectra to elucidate several features of the mechanisms involved.

The reaction rates and products of remote oxygen plasma treatment, corona discharge, and ozone treatment of high and low density polyethylenes have been examined using x-ray photoelectron spectroscopy. The oxygen uptake by remote plasma treatment was faster than that of other surface treatments using excited oxygen species. A steady state concentration of 18 ± 1% oxygen can be attained within 1 s of exposure in the remote plasma.

ESCA and contact angle measurements were used to characterize the surfaces of Polyethylene and polypropylene films exposed to SF₆, CF₄, and C₂F₆ plasmas. None of these gases polymerized in the plasma. However, all plasma treatments grafted fluorinated functionalities directly to the polymer surfaces. SF₆ plasmas graft fluorine atoms to a polyolefin surface. CF₄ plasmas also react by a mechanism dominated by fluorine atoms, but with some contribution from CF_x-radical reactions. Although C₂F₆ does not polymerize, the mechanism of grafting is still dominated by the reactions of CF_x radicals. For all gases studied, the lack of polymerization is attributed to competitive ablation and polymerization reactions occurring under conditions of ion bombardment.

The efficacy of vacuum ultraviolet irradiation for oxidizing the surface of cellulose fibers was compared to that of the conventional wet and dry processes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 357–361, 1999
https://onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291099-0518%2819990201%2937%3A3%3C357%3A%3AAID-POLA13%3E3.0.CO%3B2-2

We demonstrate that stable microwave-coupled atmospheric pressure nonequilibrium plasmas (APNEPs) can be formed under a wide variety of gas and flow-rate conditions. Furthermore, these plasmas can be effectively used to remove surface contamination and chemically modify polymer surfaces. These chemical changes, generally oxidation and crosslinking, enhance the surface properties of the materials such as surface energy. Comparisons between vacuum plasma and atmospheric plasma treatment strongly indicate that much of the vacuum-plasma literature is pertinent to APNEP, thereby providing assistance with understanding the nature of APNEP-induced reactions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 95–109, 2002
https://onlinelibrary.wiley.com/doi/abs/10.1002/pola.10056

Average values for dispersion γ_s^d and polar γ_s^d contributions of the solid surface tension γ_s γ_s^d + γ_s^p for poly(methylene oxide) (PMO) and Na-treated polytetrafluoroethylene (PTFE) are determined by a new computational analysis of wettability data. PMO displays γ_s^d equals; 21.8 ± 0.9 and γ_s^p = 11.5 ± 1.5 dyn/cm while Na-treated PTFE displays γ_s^d = 36.1 ± 3.0 and γ_s^p = 14.5 ± 2.9 dyne/cm. These surfaces present the highest fractional surface polarity p_s = γ_s^p/γ_s = 0.29-0.35 yet encountered for organic polymers or oriented monolayers. These unusual surface tension properties are correlated with surface chemistry and adhesion phenomena.

The morphological character of the surface region of polyethylene has been considered with respect to adhesion and adhesive joint strength. By melting polyethylene onto a high-energy surface (e.g., aluminum) we have provided for extensive nucleation and the formation of a transcrystalline region in the polymer. Dissolution of the metal rather than peeling the metal from the polymer leaves the surface region of the polymer intact. The polymer sheet is now amenable to conventional adhesive bonding and forms a strong adhesive joint. We conclude from this study that the occurrence of the normal weak boundary layer is a consequence of the morphology of the surface region of the material and is, therefore, influenced by the method of preparation.

Heterogeneous nucleation and crystallization of FEP Teflon and nylon 6 melts against high energy surfaces (i.e., gold) produce an interfacial region, in these polymers, of high mechanical strength. Dissolution of the metal substrate rather than removal by mechanical means results in a polymer surface which is amenable to conventional structural adhesive bonding. Nucleation and crystallization of the polymer melts in contact with phases of low surface energy (e.g., vapor) result in the generation of weak boundary layers.

The contact angle of a water droplet on the surface of a solid polymer or hydrogel (water-swollen three-dimensional network) depends on whether a hydrophilic moiety of the polymer molecule is oriented towards the air interface or towards the bulk of the solid, but not on the hydrophilicity of the molecule. Therefore, the short-range rotational mobility of a polymer molecule has a major influence on the apparent hydrophilicity of a polymer surface as measured by the contact angle of water. By the came principle, the abnormally large hysteresis effect observed in advancing and receding contact angles of water on some polymer surfaces can be attributed to the reorientation of hydrophilic moieties of polymer molecules at the surface. These factors are demonstrated by selected polymer surfaces with different degrees of mobility at the polymer-air interface.

Macromolecules at the surface of a polymeric solid have considerable mobility, and the specific arrangement of functional groups of macromolecules at the surface is dictated by the environmental conditions in which the surface is placed. Consequently, the change of environmental conditions, such as immersion in water or placement in a biological surrounding, could cause a cosiderable degree of change in the surface characteristics of a polymer from those evaluated in the laboratory against ambient air. The mobile nature of a polymer surface can be investigated by surface-implanting fluorine-containing moieties, mainly—CF₃, by the plasma implantation technique and following the disappearance and reappearance of fluorine atoms on the surface. The disappearance rates (based on the immersion time in water at room temperature) of ESCA F_1s signals, the decay rates of (advancing) contact angle of water, and the recovery of these values on heat treatment of water-immersed samples were measured as a function of crystallinity of polymer samples (at three levels of crystallinity) for poly(ethylene terephthalate) and nylon 6.