In this paper, the corona charge stability in electret polytetrafluoroethylene Teflon film is investigated after the film is treated by radio-frequency plasma. It is found that the charge stability depends strongly on the plasma composition and the film exposure to plasma, especially for negative charge. When a non-metalized film is held horizontally on the ground holder, i.e. with one side facing the plasma, oxygen plasma treatment achieves a superior negative charge retention on the front side, while its rear side retention decreases significantly. Under the same conditions in oxygen/helium and helium plasmas, the charge stability also increases but the potentials are lower compared with pure oxygen plasma after annealing. In a hydrogen plasma, the stability only slightly enhances. If the film is held vertically on the holder, so that both sides contact the plasma, the surface potential on both sides decreases dramatically and arrives at a few volts within 2 min, after annealing at 170°C. By Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), we conclude that oxidation formed on the front side is responsible for increasing the stability of negative charge. The positive carriers, generated in the film during plasma treatment, recombine with charge from corona charging and causes the surface potential in the rear side of the horizontal non-metalized film, or in both sides of the vertical non-metalized film, to discharge after heating.

We examined the possibility of the surface modification of hydrophobic polystyrene (PS) and poly(methyl methacrylate) (PMMA) by ozone aeration, UV irradiation and combination of ozone aeration and UV irradiation (ozone/UV) in distilled water. The surface states of treated films and particles were investigated by means of contact angle, atomic force microscopy (AFM) and FT-IR measurements. According to the contact angle measurements, the values of the contact angle of ultrapure water on treated PS films decreased with an increase in the elapsed time of the treatments. The most remarkable decrease was seen in ozone/UV treatment. On the other hand, the contact angle on treated PMMA films slightly increased to an equal extent after three types of treatments. The film and the particle surfaces of PS with aromatic rings were found to be well modified with hydroxyl (OH) and carbonyl (CO) groups and to give the most remarkable effects in ozone/UV treatments, whereas those of PMMA with no aromatic ring were hardly modified, merely resulting in a slight disorder in their surface roughness. The experimental results on surface modification of PS and PMMA revealed that the ozone/UV treatment in distilled water is usable as one of the useful techniques for the surface modification of polymers with aromatic rings.

The adhesion strength of a perfluorinated dielectric adhesive to polyphenylene sulfide (PPS) was investigated. The effect of different fillers in the PPS as a function of plasma treatment conditions was evaluated. The change in adhesion as a result of thermal baking was also addressed. The surface composition and surface energy were monitored and systematically quantified by X-ray Photoelectron Spectroscopy (XPS) and contact angle measurements, respectively. The correlations between the presence of certain functional groups, change in surface energy and polarity, and variation in adhesion properties indicate that the adhesion mechanism is mainly due to van der Waals forces. Enhanced wetting at the adhesive/substrate interface and a deeper interfacial diffusion zone are found to be necessary conditions to achieve the optimal adhesion.

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.

The retention of chemical structure and functional groups during plasma polymerisation was investigated. Usually plasma polymer layers, prepared by continuous wave radio-frequency plasma, are often chemically irregular in their structures and chemical compositions. To minimise these irregularities, low wattages and the pulsed plasma technique were applied to avoid fragmentations. The polymerisation of vinyl and acryl-type monomers was strongly enhanced in the dark phase (plasma-off) of a pulsed rf plasma caused by the reactivity of the vinyl or acryl-type double bonds. Bifunctional monomers with acryl or allyl double bonds and also polar groups such as OH, NH2, and COOH were used to produce plasma polymers with defined (regular) structures and a high density of a single type of functional groups. The maximum yields were 30 OH, 18 NH2, 24 COOH groups per 100 C atoms. To vary the density of functional groups a chemical copolymerisation with “chain-extending” comonomers such as butadiene and ethylene was initiated in the pulsed plasma. The composition of these copolymers was investigated by XPS and IR spectroscopy. Homopolymers and copolymer layers were deposited on polypropylene (PP) foils and then aluminium was thermally evaporated. The peel force increased considerably and showed a dependence on the density of functional groups. The plasma polymer deposition was also monitored in situ by the Self-Exciting Electron Resonance Spectroscopy (SEERS) to show correlations between plasma parameters and properties of the deposited plasma polymer layers measured “quasi-in situ” by coupling the plasma chamber with an XPS spectrometer.

A method and apparatus are taught for treating paper webs for obtaining the proper surface characteristics to promote adhesion of nonphotosensitive coating materials and/or layers typically coated thereon. The web is passed through a high-voltage sheath region or dark space of the plasma generated by a powered electrode residing in a discharge zone. The frequency of the driving voltage must be above a lower bound dictated by the properties of the paper support and the plasma, and it must be below an upper bound beyond which the sheath voltages drop significantly and it is observed that the benefits of this approach diminish. The dark space is generated by a treatment electrode in a treatment zone. There is a counter electrode having a surface area in said treatment zone which is at least as great as the surface area of the treatment electrode. A power supply is included for driving the treatment electrode with an oscillating high voltage at a frequency less than about 2 MHz and greater than 1/t_c where t_c is the charging time of a web surface exposed to a rms ion current in the plasma.

Barrier discharges (BDs) produce highly non-equilibrium plasmas in a controllable way at atmospheric pressure, and at moderate gas temperature. They provide the effective generation of atoms, radicals and excited species by energetic electrons. In the case of operation in noble gases (or noble gas/halogen gas mixtures), they are sources of an intensive UV and VUV excimer radiation. There are two different modes of BDs. Generally they are operated in the filamentary one. Under special conditions, a diffuse mode can be generated. Their physical properties are discussed, and the main electric parameters, necessary for the controlled BD operation, are listed. Recent results on spatially and temporally resolved spectroscopic investigations by cross-correlation technique are presented. BDs are applied for a long time in the wide field of plasma treatment and layer deposition. An overview on these applications is given. Selected representative examples are outlined in more detail. In particular, the surface treatment by filamentary and diffuse BDs, and the VUV catalyzed deposition of metallic layers are discussed. BDs have a great flexibility with respect to their geometrical shape, working gas mixture and operation parameters. Generally, the scaling-up to large dimensions is of no problem. The possibility to treat or coat surfaces at low gas temperature and pressures close to atmospheric once is an important advantage for their application.

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.

The capacity of a cold atmospheric-pressure air plasma (CAAP) device for advanced first aid is presented. Using swine as an animal model, two trials: 1) a large, curved cut in hindquarters area and 2) amputation of a front leg, were performed. Cold atmospheric-pressure air plasma effluent, which carries reactive oxygen species (ROS) atomic oxygen (OI), is applied for wound treatments. Swift hemostasis of the wounds by the CAAP treatment was demonstrated. The pressure applied by a finger on the cut arteries in trial 1 and the tourniquet applied in trial 2 could be removed immediately after the treatment and there was no re-bleed in both cases. CAAP hemostasis mechanism was explored via in-vitro tests. The tests on sodium citrate mixed blood-droplet samples show that 1) the heat delivered by the CAAP has no impact on the observed clot formation, 2) plasma effluent activates platelets to promote coagulation state and cascade, and 3) the degree of clotting increases with the total amount of applied OI by means of the CAAP effluent. It took only 16 s of the CAAP treatment to reach full clotting, which was considerably shortened from the natural clotting time of about 25 minutes. The tests on smeared blood samples show that the reduction of the platelet count and the increase of RBC count are proportional to the amount of applied OI. A plausible CAAP hemostasis mechanism is concluded from the in vitro test results and the animal model trials.

Commercial polyvinylchloride (PVC) sheets were treated by plasma immersion ion implantation, PIII. Samples were immersed in argon glow discharges and biased with 25 kV negative pulses. Exposure time to the bombardment plasma changed from 900 to 10,800 s. Through contact angle measurements, the effect of the exposure time on the PVC wettability was investigated. Independent of t, all samples presented contact angles, θ, equal to zero after the treatment. However, in some cases, surface hydrophilization was not stable, as revealed by the temporal evolution of θ. Samples bombarded for shorter periods recovered partially or totally the hydrophobic character while the one exposed for the longest time stayed highly hydrophilic. These modifications are ascribed to the Cl loss and O incorporation as shown by XPS measurements. Furthermore, the mobility of surface polar groups and the variation in the cross-linking degree can also affect the PVC wettability.

The comparison of corona-treated and flame-treated polypropylene (PP) films provides insight into the mechanism of these surface-oxidation processes. Atomic force microscopy (AFM), contact-angle measurements, and X-ray photoelectron spectroscopy (XPS or ESCA) were used to characterize surface-treated biaxially oriented PP. While both processes oxidize the PP surface, corona treatment leads to the formation of water-soluble low-molecular-weight oxidized materials (LMWOM), while flame treatment does not. Computational modeling of the gas-phase chemistry in an air corona was performed using a zero-dimensional plasma-chemistry model. The modeling results indicate that the ratio of O to OH is much higher in a corona discharge than in a flame. Chain scission and the formation of LMWOM are associated with reactions involving O atoms. The higher ratios of O to OH in a corona are more conducive to LMWOM production. Surface-oxidized PP exhibits considerable thermodynamic contact-angle hysteresis that is primarily caused by microscopic chemical heterogeneity.

A corona discharge treatment of low-density polyethylene film (LDPE) was carried out in preparation for flexographic printing. Such treatment of the PE film is necessary if maximum adhesion of ink is to be achieved. This project involved three different treating machines for which the current had to be manipulated in all the machines so that a standard treatment could be accomplished. Using a mathematical relation, current requirements for each machine were calculated and used to standardize treatment level of PE films. Standardization was achieved by controlling input current in all the three machines so as to attain a treatment level of 38 dynes/cm. This level of treatment showed the best results in adhesion of ink to the PE film during printing. The exercise also confirmed that printing must be carried out within 24 h of treatment since the level of treatment deteriorates with time.

Surface potential decay after negative corona charge deposition has been studied for polypropylene films 50μm thick, over a wide range of decay times and charging voltage (500–2800V). At low initial potential (500–800V), the surface potentials were stable and did not decay. At high initial potential (1200–2800V), the surface potential decay has been clearly observed with differences in the decay rate. The observed decay behavior has been computer simulated to elucidate the transport mechanism in polypropylene films. A good agreement between measured and calculated decay curves was obtained with a model in which charges are transported by hopping of injected carriers between localized trapping centers. The model is characterized by parameters such as the free carrier mobility, the mean free time of carrier between traps and the mean capture time in trap. The transport parameters have been determined by a fitting procedure.

A series of low-density polyethylene (LDPE) surfaces, chemically modified using a number of oxidative techniques employed for adhesion enhancement (pretreatments), have been studied by time-of-flight (ToF) SIMS and XPS. The methods consisted of corona discharge, flame, electrochemical, chromic acid, acid dichromate and acid permanganate treatment. All except flame treatment were performed under mild and fairly severe conditions to yield a range of surface chemistries. The XPS analysis, using high energy resolution and a refined approach to C 1s curve-fitting, provided some new insights into the quantitative assessment of the type and concentration of functional groups. Both positive and negative ion ToF-SIMS spectra were obtained at high mass resolution. The oxygen-containing fragments were identified by accurate mass analysis and subjected to a detailed comparison with the XPS results. No convincing relative intensity correlations could be identified that would allow particular secondary ion fragments to be associated strongly with particular functional groups (in this multi-functional surface situation). Inorganic residues resulting from wet chemical treatments were also investigated and here the two techniques were found to be more complementary. Copyright © 2003 John Wiley & Sons, Ltd.
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/sia.1515

Polyester fabric was treated by corona discharge irradiation at different voltages. The treated fabric showed increased wicking and hydrophilic properties and the properties can be preserved for a long time. Dyeing of the treated fabric showed that dyeing speed and the dye-uptake were improved. Surface affinity between the treated fabric surface with modified starch sizing was also confirmed to be increased. This is generally useful for the sizing of polyester staple yarn and the polyester fabric dyeing. All the results are supposed due to the improved hydrophilic properties produced by the corona discharge treatment.

The surface characteristics of polymers are important factors determining their interfacial properties and their technological performance. Changes in physical and chemical properties of a polymer film may be induced by subjecting the material to a variety of surface modification techniques, one of which is ion-beam modification. In order to understand the underlying mechanisms X-ray photoelectron spectroscopy (XPS) was used to study the alterations of the polystyrene (PS) surface after Ar-ion treatment under well controlled conditions with low ion doses from 10¹² to 10¹⁶ cm^-2. The ion bombardment leads to surface functionalization, loss of aromaticity, and free radical formation. Induced surface cross-linking and the formation of polar groups raised the surface glass transition temperature of PS film.

Polystyrene, a polymer extensively used in the biomedical field, causes a problem for some applications because of its surface hydrophobicity. Nitrogen plasma could transform this shortage through polar group attachment. To understand the role of hydrogen during surface functionalization in the nitrogen cold plasma, the effects of the nitrogen and the mixture of N₂/H₂ plasma are investigated by both the examinations of the densities of attached amine groups and the in-situ diagnostic analyses such as optical emission spectroscopy and mass spectrometry. An increase of functionalization has been proved to be controlled by the gaseous NH radical formation when H₂ is added.

The effectiveness of the treatment with ultraviolet light (UV) on several polymeric surfaces has previously been established. In this study, a low pressure mercury vapour lamp was used as a source of UV radiation for the surface treatment of a difficult-to-bond block styrenebutadiene-styrene rubber (S6), the treatment time ranging from 10 s to 30 min. The UV-treated S6 rubber surfaces were characterized by contact angle measurements (ethylene glycol, 25°C), ATR-IR spectroscopy, XPS, Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). T-peel tests on UV-treated S6 rubber/polyurethane (PU) adhesive/ leather joints (before and after ageing) were carried out to quantify adhesion strengths. The UV treatment of S6 rubber produced improved wettability, the formation of CO, CO and COO moieties, and ablation (removal of a thin rubber layer from the surface). The extent of these modifications increased with increasing treatment time. The extended UV treatment produced greater surface modifications, as well as the incorporation of nitrogen moieties at the surface. Furthermore, noticeable ablation of S6 rubber surface occurred. Peel strength values increased with increased treatment time of UV treatment of S6 rubber. Also, with increasing treatment time, the adhesive joints showed different loci of failure: adhesional failure for the as-received and 2 min-UV treated S6 rubber/polyurethane adhesive/leather joints changed to mixed failure (cohesive in the treated S6 rubber + adhesional failure) for the 30 min-UV treated S6 rubber/polyurethane adhesive/leather joint.

One of technologically imminent problems related to the use of pressure sensitive adhesives (PSAs) in the LCD industry is how to properly control the surface properties of various polymeric films used in devices to obtain sufficient bond strength with PSAs. To provide practical solutions to this issue, we used two types of surface treatments, NaOH and corona, to control the surface properties of polymeric films that are widely used in the LCD industry. Here we report a significant increase in surface tension in triacetyl cellulose (TAC) and discotic liquid crystal (D-LC) films along with a remarkable enhancement of bond strength in TAC/PSA and D-LC/PSA systems. The major portion of surface tension increase, in both types of films, was found to be due to an increase of polar component. The continuous increase of OH functionality in TAC with NaOH treatment time supported this observation. Furthermore, we established a map of surface treatment by studying the sequential effects of the two treatments, and based on this, we clearly demonstrated that each treatment had its own limiting value that could not be altered regardless of the sequence of surface treatment.

Ethylene-co-tetrafluoroethylene copolymer (ETFE) films were modified by four plasmas: direct and remote H2 plasmas and direct and remote O2 plasmas; and the hydrophobic recovery process of these plasma-modified surfaces was investigated using water contact angle measurements and angular XPS. The water contact angle measurements showed important aspects for the hydrophobic recovery process. (1) All plasma-modified ETFE surfaces, regardless of the kind and mode of plasmas, showed increases in the contact angle with increasing aging time. The increase continued for 5 days after finishing the plasma modification, and stopped after 5 days. (2) The plasmamodified surfaces after the aging process never reverted back to the same level of the contact angle as for the unmodified (original ETFE) surfaces. (3) The contact angle after the aging process was strongly dependent on to what plasma the ETFE surfaces were exposed in the modification. (4) The aging temperature influenced the contact angle value after the aging process. The angular XPS measurements also provided a detailed description of the chemical composition of the topmost layer. (1) The chemical composition at the topmost layer of the surfaces altered during the aging process. (2) CH₂-CH₂-CHF, and CH₂-CHF-CH₂ and CH₂-CH(OH)-CF₂ groups disappeared from the topmost layer during the aging process; and CH₂-CH₂-CH₂, and CH₂-CH₂-CF2 and CH₂-CH(OH)-CHF groups appeared at the topmost layer. (3) Such disappearance and appearance occurred on all plasma-modified surfaces regardless of the kind (H₂ or O₂ plasma) or mode (direct or remote plasma) of plasmas used for the modification. This may be due to segmental mobility of CH₂-CH₂-CH₂ sequences rather than of CF₂-CF₂-CF₂ sequences.

The acid-base theory as developed by van Oss, Chaudury and Good is a powerful tool to analyze the surface free energy of polymeric materials; however, some problems are encountered in its application and some authors have shown that these problems can be theoretically solved considering this theory as an example of the so-called LFER theories. From this point of view, the definition of a well-defined scale of acid-base strength and the use of a wide and well-equilibrated, appropriate set of liquids is very important. In the present paper some recent results are presented which are based on the mathematical approach discussed by Della Volpe and Siboni in previous papers. The treatment is developed as a list of questions, Frequently Asked Questions (FAQs), whose theoretical implications are discussed using numerical examples chosen from the literature. Some literature data, collected by the opponents of the acid-base theory and recently published, are re-analysed using these methods, showing that they constitute a well-defined set to calculate, with a good precision, the acidbase components of the considered materials and the interfacial energies of liquids used. The present paper is the premise of a second one, in which a set of contact angles data collected by the authors and by other researchers will be analysed following the principles discussed here.

The effect of ion implantation including ion species (N₂ and C₃H₈⁺) and the fluences (1x10¹⁴-5x10¹⁵ ions/cm²) on the surface energy of ultrahigh molecular weight polyethylene (UHMWPE) were investigated. The total surface energy increases significantly after implanting with the fluence of 1x10¹⁴ ions/cm² regardless of ion species, then, the total surface energy slightly increases for N₂⁺ implanted UHMWPE and decreases slightly for C₃H₈⁺ implanted UHMWPE with a further increase of fluence. The structural changes of UHMWPE with different fluence for different ion species are very similar. The linear chains of UHMWPE are damaged and cross linking is generated after implantation. As the fluence increases, the polymer surface becomes more disordered, and the surface becomes hydrogenated amorphous carbon when the fluence exceeds 1x10¹⁵ ions/cm². The surface roughness increases with the increase of the fluence regardless of ion implantation species.

Plasma treatment of polymers encompasses a variety of plasma technologies and polymeric materials for a wide range of applications and dates back to at least the 1960s. In this article we provide a brief review of the United States patent literature on plasma surface modification technologies and a brief review of the scientific literature on investigations of the effects of plasma treatment, the nature of the plasma environment, and the mechanisms that drive the plasma–surface interaction. We then discuss low‐radio‐frequency capacitively coupled nitrogen plasmas and their characteristics, suggesting that they provide significant plasma densities and populations of reactive species for effective plasma treatments on a variety of materials, particularly when placing the sample surface in the cathode sheath region. We further discuss surface chemical characterization of treated polymers, including some results on polyesters treated in capacitively coupled nitrogen plasmas driven at 40 kHz. Finally, we connect plasma characterization with surface chemical analysis by applying a surface sites model to nitrogen uptake of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) treated in a 40 kHz nitrogen plasma. This example serves to suggest an interesting practical approach to comparisons of plasma treatments. In addition, it suggests an approach to defining the investigations required to conclusively identify the underlying treatment mechanisms.