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.

Low-pressure plasma was selected as a surface treatment to improve the painting properties of elastomeric polyethylene (PE). Several experimental variables in the low-pressure synthetic air plasma treatment were considered: time of the treatment, plasma power and pressure inside the chamber. The durability of the treatment effects was also studied. Contact-angle measurements (water, 25 C) showed an increase in the wettability of elastomeric PE after treatment with plasma, which corresponds to an increase in the O/C ratio on the treated surface. In fact, different oxygen-containing groups were created on the PE surface. The more intense and longer the plasma treatment, the greater the degree of surface oxidation, up to a certain value. The painting properties of the material were evaluated by joints produced with as-received and treated elastomeric PE and an acrylic paint and using T-peel tests. Peel strength values increased after low-pressure plasma treatment, especially after the first 3 s of treatment with a power of 200 W; and an adhesion failure between the paint and the adhesive tape was obtained. This failure was maintained during four hours after the treatment. For longer treatment times the paint does not adhere to the material, the peel-strength values decrease and the contact angles increase, indicating that the effects of the surface modifications are not maintained.

The present work focuses on the deposition of fluorocarbon (FC) films on aluminum and SiO2 surfaces, and addresses the issue of selective deposition on Al versus SiO2 in order to obtain surfaces of distinctly different wettability. If this is achieved, hydrophobic/hydrophilic patterning of substrates would be feasible by means of a self-aligned and relatively simple method. The selectivity of the deposition is optimized through proper selection of the deposition conditions, mainly gas-mixture composition and deposition time, and is demonstrated by means of contact-angle measurements on Al and SiO2 surfaces. Chemical (XPS) analysis of the FC films deposited under various conditions is also performed and correlated with the wettability of the plasma-modified Al surfaces.

This study systematically characterises a matrix of water-based flexographic inks with respect to their rheology, surface tension and wetting of liquid packaging board, to provide a basis for interpretation and prediction of their printing performance. For all pigment and acrylate polymer vehicles and mixing proportions the inks were shown to be shear thinning and thixotropic, with plastic viscosity, yield stress and storage and loss moduli increasing strongly with content of solution polymer (at comparable solids contents). The solution polymer decreases the static surface tension of the inks, but generally leads to an increase in their equilibrium drop contact angle on the polyethylene- (PE-) coated board due to increase in the ink-board interfacial energy. The solution polymer also decreases the drop spreading rate, and a simple model is tested to express the spreading dynamics in terms of equilibrium contact angle and a rate parameter given by the effective ratio of surface tension to viscosity.

Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (PET) film surface for improving hydrophilicity using the non-thermal plasma generated by atmospheric pressure glow discharge (APGD) in air is conducted. The discharge characteristics of APGD are shown by measurement of their electrical discharge parameters and observation of light-emission phenomena, and the surface properties of PET before and after the APGD treatment are studied using contact angle measurement, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEh4). It is found that the APGD is homogeneous and stable in the whole gas gap, which differs from the commonly filamentary dielectric barrier discharge (DBD). -4 short time (several seconds) APGD treatment can modify the surface characteristics of PET film markedly and uniformly. After 10 s APGD treatment, the surface oxygen content of PET surface increases to 39%, and the water contact angle decreases to 19°, respectively.

Digital printing is increasingly being used for package printing. One of the major techniques of digital printing is dry-toner electrophotography. This paper evaluates the printability of three different extrusion coatings used for packaging boards: low-density polyethylene (PE-LD), ethylene methyl acrylate (E/MA) and polyethylene terephthalate (PET). Extrusion coatings in general have an impervious, chemically inert, nonporous surface with low surface energies that cause them to be non-receptive to bonding with toners. The most common methods used in improving the adhesion properties of polymer coatings are different surface treatments. These increase the surface energy and also provide the polar molecular groups necessary for good bonds between the toner and polymer molecules. The polymer coatings have been modified with electrical corona discharge treatment. The effects of corona on polymer surfaces and the correlation between surface modification and print quality have been evaluated. Results show that sufficiently high surface energy and surface-charge uniformity are necessary for even print quality and toner adhesion. E/MA and PET have the required surface-energy level without the corona treatment, but PE-LD needs surface modification in order to succeed in the electrophotographic process. E/MA also has exceptional surface-charge properties compared with PET and PE-LD. Polym. Eng. Sci. 44:2052–2060, 2004. © 2004 Society of Plastics Engineers.

The surface degradation and production of low molecular weight oxidized materials (LMWOM) on biaxially oriented polypropylene (BOPP) and low-density polyethylene (LDPE) films was investigated and compared for two different dielectric barrier discharge (DBD) treatment types, namely air corona and nitrogen atmospheric pressure glow discharge (N₂ APGD). Contact angle measurements, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) analyses were performed in conjunction with rinsing the treated films in water. It is shown that N₂ APGD treatments of both polyolefins result in much less surface degradation, therefore, allowing for a significantly higher degree of functionalization and better wettability. Hydrophobic recovery of the treated films has also been studied by monitoring their surface energy (γ_s) over a period of time extending up to several months after treatment. Following both surface modification techniques, the treated polyolefin films were both found to undergo hydrophobic recovery; however, for N₂ APGD modified surfaces, γ_s ceases to decrease after a few days and attains a higher stable value than in the case of air corona treated films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1291–1303, 2004
https://onlinelibrary.wiley.com/doi/abs/10.1002/app.21134

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

This paper describes the photochemical surface modification of polystyrene (PS) substrates using vacuum ultraviolet (VUV) light 172 nm in wavelength. We have particularly focused on the effects of atmospheric pressure during VUV irradiation on the obtained surface's wettability and the stability of the wettability, in addition to its chemical structure, morphology, and photooxidation rate. Samples were photoirradiated with VUV light under pressures of 10, 10(3), or 10(5) Pa. Although, in each case, the originally hydrophobic PS surface became highly hydrophilic, the final water-contact angle and photooxidation rate depended on the atmospheric pressure. The samples treated at 10 Pa were less wettable than those prepared at 10(3) and 10(5) Pa due to the shortage of oxygen molecules in the atmosphere. The minimum water-contact angles of the samples treated at 10, 10(3), and 10(5) Pa were about 8 degrees, 0 degrees, and 0 degrees, respectively. With the samples prepared at 10 and 10(3) Pa, photooxidation reactions proceeded in the topmost region closest to the surface, while at 10(5) Pa photooxidation was found to be greatly enhanced in the deeper regions, as evidenced by angle-resolved X-ray photoelectron spectroscopy. Photoetching rates were determined through atomic force microscope observation of microstructured PS samples prepared by a simple mesh-contact method. As estimated from AFM images of the latticed microstructures obtained, the rates of samples prepared at 10(3) and 10(5) Pa were about 1.5 and 1.3 nm/min, respectively. However, no photoetched features were observable on the sample surface prepared at 10 Pa. Hydrophilic stability also varied greatly depending on atmospheric pressure. The hydrophilicity of samples treated at 10 and 10(3) Pa gradually decreased as they were exposed to air. On the other hand, the sample surface prepared at 10(5) Pa showed excellent hydrophilicity even after being left in air for 30 days.

Film samples of low-density polyethylene (LDPE) and biaxially oriented poly(propylene) (BOPP) were surface modified by vacuum ultraviolet (VUV) irradiation using a Kr resonant lamp at λ = 123.6 nm in low-pressure ammonia gas, and were then stored in air. The time-dependence of the surface properties was monitored using several complementary surface-sensitive techniques such as contact angle goniometry (CAG), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS), which allows one to determine the surface energy, and chemical composition at different depths. The relative importance of four possible mechanisms involved in surface hydrophobic recovery is discussed, and we show that in our particular case the main mechanism is rotational and/or translational motion of polymer chains and chain segments. This restructuring determines the observed “loss” of functional groups, which occurs within the first few monolayers of the surface (∼1 nm), as shown by the ToF-SIMS results, and which leads to the observed decrease in the surface energy. In the deeper surface regions (∼10 nm) long-lived radicals react with oxygen and water vapor upon exposure to the atmosphere, leading to an increase in the concentration of bound oxygen, as observed by XPS. Finally, CAG measurements show that the hydrophobic recovery is reversible and can be significantly reduced by cross-linking near the surface, as illustrated by depth sensing nano-indentation measurements on BOPP surfaces.

Polystyrene (PS) and polyethylene (PE) samples were treated with argon and oxygen plasmas. Microwave electron cyclotron resonance (ECR) was used to generate the argon and oxygen plasmas and these plasmas were used to modify the surface of the polymers. The samples were processed at different microwave powers and treatment time and the surface modification of the polymer was evaluated by measuring the water contact angle of the samples before and after the modification. Decrease in the contact angle was observed with the increase in the microwave power for both polystyrene and polyethylene. Plasma parameters were assessed using Langmuir probe measurements. Fourier transform infrared spectroscopy showed the evidence for the induction of oxygen-based functional groups in both polyethylene and polystyrene when treated with the oxygen plasma. Argon treatment of the polymers showed improvement in the wettability which is attributed to the process called as CASING, on the other hand the oxygen plasma treatment of the polymers showed surface functionalization. Correlation between the plasma parameters and the surface modification of the polymer is also discussed.

The theoretical analysis of electrostatic interactions and ion redistribution in the close vicinity of the three-phase contact line shows their important role in the Langmuir wetting process. To provide a sufficient rate for the ion transfer, which is intended to neutralize the interfacial charge, the concentration and potential distributions deviate from the equilibrium. As a consequence, during the deposition process the adhesion work, and hence the contact angle, are defined by the local ionic concentrations near the three-phase contact line. The concentration profiles and the electro-diffusion ion fluxes induced during the Langmuir wetting process are strongly dependent on the subphase composition and on the monolayer properties. The results of the analysis are in a good agreement with the experiments.

The objectives of this work were to identify, develop and compare methods for opti-mized welding of polypropylene using the ultrasonic method. The methods considered include: modification of surface polarity by grafting monomers onto polypropylene backbone, thermal and chemical surface pretreatments and surface pretreatment by excimer laser ablation. The weld joint tensile strength was chosen as the optimization criterion for ultrasonic welding. The thermal properties and weld morphology obtained using Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM), respectively, were correlated to weld strength. It was determined that proper surface modification improved material weldability. The results suggest that increased polarity and roughness and decreased melting temperature and heat of melting increase the weld strength.

Ultrahigh molecular weight polyethylene (UHMWPE) fibers were treated using pulsed KrF (248 nm) excimer laser in air and in diethylenetriamine (DETA), to improve their adhesion to epoxy resin. The effects of fluence, number of pulses and the treatment environment were explored. Topographical and chemical changes on the fiber surface were characterized using several techniques, including X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic wettability measurements. SEM micrographs and AFM images revealed that the surface roughness of fibers increased after the laser treatment and was a function of the fluence (energy density) of the laser beam and number of pulses. The XPS data indicated that oxygen and nitrogen were incorporated on the fiber surfaces making them more polar. The dynamic wettability data confirmed the presence of polar groups on the fiber surfaces. The UHMWPE fiber/epoxy resin interfacial shear strength (IFSS) increased by up to 600% for some treatment conditions. Introduction of polar groups and increased surface roughness are two main factors that contribute to the increased adhesion (IFSS) of the UHMWPE fiber/epoxy resin system significantly.

The effects of exposure to [72 nm ultraviolet (UV) excimer light in ambient air on the wettability and surface free energy of polymer films were investigated from contact angle measurements. The polymer films used were polyethylene (PE), polypropylene (PP), poly (ethylene terephthalate)(PET), nylon 6 (Ny6) and polyimide (Pl). As a measure of the wettability, the water contact angle was determined by the sessile drop and the Wilhelmy methods. For all films, considerable increase in wettability was accomplished by UV exposure within a few tens of seconds. After the UV exposure, a decrease in the wettability, the hydrophobic recovery, was observed over a time period of several days. Even after the recovery, the wettability was sufficiently higher compared to that before the UV exposure. The Lifshitz-van der Waals component and Lewis acid-base parame-ters of the surface free energy of the films were determined by contact angle measurements using certain probe liquids. The base parameter was found to increase considerably by the UV exposure. XPS analysis and AFM observation of the film surfaces showed that such increases in the wettability and the surface free energy were due to the increased atomic oxygen concentration at the film surfaces. The effect of the UV exposure on particle deposition onto PP and PET in water was also examined using spherical polyethylene and nylon 12 particles. The apparent equilibrium number of particles deposited on the polymer substrate decreased drastically after UV exposure. The particle deposition behavior was explained well in terms of the free energy change due to deposition, which was calculated from various surface free energies.

Abstract Application of a pulsed high negative voltage (approx. 10 us pulse width, 300-900 pulses per second (pps)) to a substrate is found to induce discharge and thereby increase the ion current of an inductively coupled plasma. This plasma source ion implantation (PSII) technique is investigated as a surface modification method for poly (ethylene terephthalate)(PET) films using Ar, N2 and CZHZ gases. PSII treatment of PET with N2 and Ar gases is found to change the color of the PET film, effectively increasing the near-ultraviolet absorption. The effects of the treatment using N2 and Ar gases on the chemical bonding of C, H and O are examined by X-ray photoelectron spectroscopy (XPS). PSII treatment with CZHQ gas is shown to produce a thin diamond-like carbon film on the PET surface. The layer is shown to be smooth by scanning electron microscopy, and the structure is analyzed by XPS and laser Raman spectroscopy. The treatment using CZHZ gas effectively reduces the oxygen transmission rate by up to 100 times that of unmodified PET film at a carbon film thickness of only 70-300 mm.

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.

Accurate surface tension of Teflon^® AF 1600 was determined using contact angles of liquids with bulky molecules. For one group of liquids, the contact angle data fall quite perfectly on a smooth curve corresponding to γ_sv = 13.61 mJ/m², with a mean deviation of only ±0.24 degrees from this curve. Results suggest that these liquids do not interact with the solid in a specific fashion. However, contact angles of a second group of liquids with fairly bulky molecules containing oxygen atoms, nitrogen atoms, or both deviate somewhat from this curve, up to approximately 3 degrees. Specific interactions between solid and liquid molecules and reorientation of liquid molecules in the close vicinity of the solid surface are the most likely causes of the deviations. It is speculated that such processes induce a change in the solid–liquid interfacial tension, causing the contact angle deviations mentioned above. Criteria are established for determination of accurate solid surface tensions.