Polyvinylidenefluoride (PVDF) was irradiated by a keV Ar⁺ ion in O₂ environment for improving adhesion between PVDF and Pt, and reaction between PVDF and the ion beam has been investigated by X-ray photoelectron spectroscopy (XPS). The adhesion test between Pt and the modified PVDF was carried out by boiling test, in which the specimens were kept in boiling water for 4 h. Two failure modes (buckling up due to weak adhesion and crack formation due to strong adhesion) of Pt films have been observed in the system. Contact angle of PVDF was reduced to 31 from 75° by the irradiation of 1 × 10¹⁵ Ar⁺ ions/cm² with oxygen flow rate of 8 sccm. The surface of the irradiated PVDF became more rough as ion dose increased. The improved adhesion mechanism and identification of newly formed chemical species have been confirmed by Carbon 1s and Fluorine 1s X-ray photoelectron core-level spectra. The main reaction occurred at the irradiated PVDF surface is an ion-beam-induced oxidation accompanied with preferential sputtering of fluorine. Newly formed chemical species at interface are regarded as ester and carboxyl groups. Adhesion of the Pt–PVDF interface was improved by ion irradiation in O₂ environment. This improvement is originated from the presence of carbon—oxygen bonds on the irradiated PVDF surface. Comparison of failure modes on the irradiated PVDF at various conditions after the boiling test shows that adhesion of Pt film is largely affected by the product of ion-assisted reaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 41–47, 1999
https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1097-4628(19990404)72:1%3C41::AID-APP4%3E3.0.CO;2-J

The concept that the solubility parameter is a vector composed of hydrogen bonding, polar, and dispersion components is proposed and applied with success to prediction of the solubility of 33 polymers and resins in 90 solvents and 10 plasticizers. Solvents and plasticizers can be located as points in a three dimensional system, and regions of solubility are found for polymers and resins when solubility data are plotted. Non-interacting solvents which in a mixture become interacting have been found with better than 95% accuracy in over 400 cases.

The concept that the solubility parameter is a vector composed of hydrogen bonding, polar, and dispersion components is proposed and applied with success to prediction of the solubility of 33 poylmers and resins in 90 solvents and 10 plasticizers. The application of the solubility parameter concept is described. The three dimensional solubility parameter system based on the homomorph concept has been developed on the basis of polymer solubility. The same system has been applied to the characterization of dyes, nonionic emulsifiers, and pigments. The system is also useful for selecting solvents when protective coatings are formulated with more than one polymeric solute.

Surface tensions of polymers can be accurately determined by observing whether droplets of liquids spontaneously spread or not. The polymer surface tension will be higher than the surface tension of a liquid which spreads, and lower than that of a liquid which remains as a droplet.

Examples of surface characterization using cohesive energy parameters and surface energy parameters are given. In general the two approaches yield essentially equivalent results. The predictive ability of the cohesive energy approach suggests its use where directed modification of surface properties is desired.

The aim of this work was to improve adhesion to tefzel using plasma surface treatment. The plasmas used were O₂, and NH₃. Joints ,ade from the adherends using several commercially available epoxy adhesives were tested using a double lap shear configuration. Measured bond strenghts for the treated adherends were as much as 30 times greater than those for the untreated materials. Examination of the O₂ plasma-treated Tefzel by electron spectroscopy for chemical analysis indicated a surface oxidation increase of about 7–8% over the untreated material, with the oxide being primarily in the form of an ester.

Contact time of activated gas with polymer film of as little as 1 sec. under these relatively mild conditions resulted in greatly improved adhesive joint strength for polyethylene. Longer contact times were required for polymers such as polytetrafluoroethylene. Helium, argon, krypton, neon, and xenon, and even hydrogen and nitrogen were all effective crosslinking agents although the latter also changed wettability of the surface. Adhesive joints were prepared by sandwiching 1041 films of polyethylene (Marlex 5003, Phillips Petroleum Co., Bartlesville, Oklahoma) and polytetrafluoroethylene (G-80, Allied Chemical Co., Morristown, New Jersey), before and after CASING, between epoxy-coated aluminum strips (3). The values obtained for tensile shear strengths of these joints are shown in Figure 1. In these instances, the polyethylene film was treated for 10 sec. and the polytetrafluoroethylene film was treated for 10 min.

No single step in the coating process has more impact on film adhesion than surface preparation. Film adhesion to a plastic is primarily a surface phenomenon and requires intimate contact between the substrate surface and the coating. However, intimate contact of that plastic surface is not possible without appropriate conditioning and cleansing. Plastic surfaces present a number of unique problems for the coater. Many plastics, such as polyethylene or the fluorinated polymers, have a low surface energy. Low surface energy often means that few materials will readily adhere to the surface. Plastic materials often are blends of one or more polymer types or have various quantities of inorganic fillers added to achieve specific properties. The coefficient of thermal expansion is usually quite high for plastic compounds, but it can vary widely depending on polymer blend, filler content, and filler type. Finally, the flexibility of plastic materials puts more stress on the coating, and significant problems can develop if film adhesion is low due to poor surface preparation.

The methods to estimate the surface tension of polymer solids using contact angles have been reviewed in the first part. They are classified into the following three groups depending on the theories or the equations applied: (1) the methods using the Young's equation alone, (2) the methods using the combined equation of Young and Good-Girifalco, and (3) the methods using the equations of work of adhesion. Some notes and comments are given for each method and results are compared with each other. The two-liquids method for rather high energy surface is also introduced.

Next, some new possibilities to evaluate the surface tension of polymer solids are presented by our new contact angle theory in consideration of the friction between a liquid drop and a solid surface. The advancing and receding angles of contact (θ_a and θ_r) are explained by the frictional tension γ_F and accordingly two kinds of the critical surface tension γ_C(γ_Ca and γ_Cr) are given.

This work has shown that one of the recommendable ways to evaluate γ_S is either the maximum γ_LV cos θ_a or the maximum γ_C using the advancing contact angle θ_a alone, and another way is the arithmetic or the harmonic mean of the γ_Ca and γ_Cr. A depiction to determine the γ_C such as ln(1 + cos θ₀) vs. γ_LV with cos θ₀ = (cos θ₀ + cos θ_r)/2 has also been proposed.

On-line corona treatment of polypropylene (PP) fibers during melt-spinning is studied. After extrusion of pp filaments, collected fiber tow is subjected to corona treatment prior to drawing, crimping, and cutting into staple fibers, and wettability, antistatic, and friction properties of treated fibers are characterized. Corona treatment results in an average decrease of 5-10° in the advancing contact angle and of 10-25° in the receding contact angle for water on fibers. With amounts of spin finish lower than 0.2% by weight of fiber, treated fibers have considerably better antistatic properties than untreated fibers. Treated fibers have an order of magnitude lower electrical resistance and about 50% less static charge build-up during carding than untreated fibers. In addition, there is a sharp change in wetting and friction properties of fibers with corona treatment when the amount of spin finish is between 0.12 and 0.13 wt %. These effects are attributed to improved wetting of the treated fibers by spin finishes, leading to a more uniform spreading of finish agents on the fiber surface.

By fluorinating the surface of a polymer, the hydrogen bonding energy of a polar surface has been defined. The contact angles for three solvent classes; nonpolar, polar and hydrogen bonding, on a polar surface results in the separation of dispersion, polar, and hydrogen bonding energies. Both critical surface tension plots and theoretical calculations were used to define the surface energy for fluorinated polyethylene.

Many coatings materials are based on polymeric materials and sometimes difficulties arise when trying to marry them to polymer substrates of low surface energy and relatively inert molecular structure. Through the application of tailored coating formulation, substrate surface pretreatment and suitable coating process these problems may be eliminated to produce coated polymers with high bond strength properties.

Poly(tetrafluoroethylene) and a fluoroethylene copolymer were surface treated with a 2.45-GHz microwave plasma to enhance their adhesion to a vinylester thermoset. The plasmas were generated with an inert gas (Ar) and with reactive gases (H₂, O₂, and N₂). The lap-joint shear stress was measured on fluoropolymer samples glued with the vinylester. In general, the stress at failure increased with increasing plasma-energy dose. The H₂ plasma yielded the best adhesion, and X-ray photoelectron spectroscopy revealed that it yielded the highest degree of defluorination of the fluoropolymer surface. The defluorination efficiency declined in the order H₂, Ar, O₂, and N₂. Contact angle measurements and scanning electron microscopy revealed that the surface roughness of the fluoropolymer depended on the rate of achieving the target energy dose. High power led to a smoother surface, probably because of a greater increase in temperature and partial melting. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 838–842, 2005
https://onlinelibrary.wiley.com/doi/abs/10.1002/app.22174

Different plasma treatments in a rf discharge of Ar, He, or N₂ are used to etch, cross-link, and activate polymers like PC, PP, EPDM, PE, PS, PET and PMMA. Due to the numerous ways a plasma interacts with the polymer surface, the gas type and the plasma conditions must be adjusted on the polymer type to minimize degradation and aging effects. Wetting and friction properties of polymers can be improved by a simple plasma treatment, demonstrated on PC and EPDM, respectively. However, the deposition of ultra-thin layers by plasma enables the adjustment of wetting properties, using siloxane-based or fluorocarbon films, and further reduction of the friction coefficient, applying siloxane or a-C:H coatings. Nevertheless, the adhesion of plasma-deposited coatings should be regarded, which can be enhanced by depositing a graded layer.

A general framework for the physical description of partial discharge (PD) processes is presented that holds for different types of PD causing defects. A PD process is treated as a stochastic process consisting of short duration discharges (point-like in time) and charge carrier drift/recombination intervals between these discharges. It is determined by few basic physical parameters and, in a stochastic process framework, can be described in a closed form by a master equation. Since usually only the fast discharges can be measured as PD signals, a restricted possibility of observing a PD process results. The link between the stochastic process and observable quantities is derived.

A specific type of measurements is reported, the so-called phase-resolved partial discharge (PRPD) patterns. Here the total charge transferred during a discharge and the time or alternating current phase at which the discharge occurs are measured. Thus each discharge event is described by the two quantities, charge and phase angle. The modelling of the observation process is explicitly derived for this case. However, the used method can easily be generalized to other types of PD measurements.

The proposed approach yields new possibilities for the interpretation and analysis of PD patterns. Features of PD patterns can be derived analytically from the process parameters. Conversely, quantitative information about the discharge physics can be gained from measured patterns. Some limiting cases of model parameter values leading to typical pattern features are discussed explicitly.

Examples are presented that demonstrate the applicability of the model for three different discharge types (internal discharge in a gas-filled void, surface discharge in oil, corona in air).

One of the parameters characterizing the surfaces of materials is the surface free energy. The most common way to determine its value is to measure the surface tension by the sessile drop method. In this case a contact angle between the surface and the edge of droplets of liquids is measured. There are various approaches to calculate the surface free energy from the contact angle measurements. We made a review and a direct comparison of the most widely used methods and testing liquids in order to re-evaluate their advantages and disadvantages. In the presented work we discuss the limits of applicability of the examined methods. We confirm that methods using a pair of liquids give results dependent on the liquids chosen. Using a pair of non-polar and polar liquid yielded most reliable results. This is even more clear when two-liquid method is transformed into a multiple-liquid method. The algorithms developed during the work will be implemented into liquid contact angle analysis software.