Although many thousands of measurements have been made to determine the pull necessary to detach a ring from the surface of a liquid, it is a surprising fact that until three years ago there was no “ring method” for the measurement of surface tension. Thus in “International Critical Tables,” nine experimental methods for surface tension are listed but a ring method is not included, since the procedure which had been designated by this term did not supply even one single measured value of surface tension of these tables.

The failure of the ring procedure was due to the fact that the theory had not been sufficiently developed to permit its use as a method of measurement, although an incomplete theory had been developed by Cantor,¹ Lohnstein,² Lenard,³ Tichanowsky⁴ and MacDougall.⁵

In 1926 Harkins, Young and Cheng,⁶ on the basis of the well-justified assumption that the capillary height method, properly applied, gives correct values for the surface tensions of suitable liquids, showed how the ring procedure could be used as a moderately accurate method for such measurements. In the present paper the method is given a still higher degree of accuracy (about 0.25%).

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.

A metallized polymeric film comprises a sulphonated copolyester intermediate adherent layer having an alkali metal content of not more than 0.005 gram atoms percent.

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.

Honolulu is a most beautiful place, suitable for all occa­ sions. Its choice as the meeting site for the first Joint Chemical Congress between the American Chemical Society and the Chemical Society of Japan was praised by scientists from both sides. During this Congress, the International Conference on Adhesion and Adsorption of Polymers was held at the Hyatt Regency Hotel between April 2 and 5, 1979. We had speakers from ten nations presenting over forty papers related to the subject matter. It was a memorable event. Unlike our two previous adhesion symposia held in 1971 and 1975, this was the first time in the same conference that we discussed both adhesion and adsorption of polymers simultaneously. These two important phenomena are not only inter-related, but also equally important in adhesive technology as well as biochemical processes. The papers presented to this Conference deal with these two phenomena from both fundamental and practical viewpoints. Furthermore, with the advance of new surface analytical techniques, the actual, microscopic happenings at the interfaces can be pin­ pointed. Thus, characterization of interface became one of the major focuses of this Conference. As a result, a broad coverage of the subject matter includes statistical thermodynamics, surface physics, surface analysis, fracture mechanics, viscoelasticity, failure analysis, surface modification, adsorption kinetics, bio­ polymer adsorption, etc. Thanks to the diligence of our contri­ butors, we are now able to publish the final papers in these two volumes.

The present invention relates to a method and apparatus for the production of plastic materials having improved surface bonding properties for bonding other materials to the plastic materials. The new method comprises passing the plastic material through an electrically charged flame. The apparatus used to perform the method may have several embodiments which include an electrical power supply circuit, a discharge electrode, a burner, and a chill-roller for supporting the plastic material.

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.

A new process, the Non Anchor Coating Extrusion Laminating Process for producing an extrusion laminated film without any chemical primer, was investigated. Good adhesive properties were obtained by combining an ozone treatment of a molten polyethylene (LDPE) web and an activation treatment of the polyamide (ONy) substrate film. The adhesion mechanism induced by the new process was studied by FT-IR, ESCA and extraction of unreacted polyamide from the laminated samples. The peel strength between the ONy and LDPE laminated films produced with this process was greater than that for laminated film made with a conventional lamination process using anchor coating agents. A model of the adhesive mechanism is proposed. Hydrogen and covalent bonds through oxygenated functional groups are responsible for the enhanced adhesion.

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.

Although the power of plasma surface engineering across vast areas of industrial manufacturing, from microelectronics to medical and from optics to packaging, is demonstrated daily, plasma in the textile industry has been cynically described as the technology where anything can happen... but never does. Research into the application of plasmas to textiles goes back to the 1960s but, despite the reporting of novel and potentially commercial effects, it is only in recent years that plasma processing systems have begun to emerge into textile manufacturing in the production of specialty/high value fabrics. It is instructive to look at major criteria for the introduction of new technology into the textile market and to assess plasma processing against such criteria. They can be separated into qualifiers (must be satisfied by the new technology as a minimum) and winners (motivate take-up of the new technology by the industry). Here are ‘qualifier’criteria for new textile technologies:

In this study we investigated the stability of poly(ethylene terephthalate) (PET) and polypropylene (PP) surfaces modified using three combinations of UV light and ozone: ozone only, UV light in air (producing ozone), and UV light in air supplemented by additional ozone in the incoming air. Analysis was done using X-ray photoelectron spectroscopy and dynamic contact angle measurements. Our results showed that PET film is oxidized using these treatment conditions and it changes significantly within the first week of aging and after washing with water. These changes are reflected in the decrease in the Δ(O : C) ratio and the increase in the contact angle. Conversely, PP changes very little on aging or washing. Low-molecular-weight oxidized material (LMWOM), produced on the polymer surfaces treated with UV/air or UV/air + ozone, is easily removed with water washing. On aging PET, a number of the oxidized groups at the surface disappear, seeming to migrate into the bulk. The PP, however, does not favour migration as a path to reduce the overall free energy of the system, so the oxidized groups remain at the surface. Treatment with ozone only, in the absence of UV light, is a much different modification process in terms of the mechanism and the functional groups formed on the surface. This is reflected in the aging and washing behaviour of both the PET and the PP treated with ozone only.

A high-temperature-vulcanized polydimethylsiloxane (PDMS) elastomer has been subjected to corona discharges for different periods of time in dry air. The loss and recovery of hydrophobicity of the surface have been characterized by contact angle measurements. Immediately after exposure to corona discharges, samples showed a low surface hydrophobicity and, on storage in dry air, a continuous increase in hydrophobicity finally approaching the hydrophobicity of the unexposed material. The activation energy of the hydrophobicity recovery was two to four times greater than the activation energy of the diffusivity of low molar mass PDMS in PDMS elastomers, indicating that the diffusivity properties of the oxidized surface layer were different from that of the bulk. PDMS elastomers quenched in liquid nitrogen or subjected to small mechanical deformation ( < 1% strain) after exposure to corona discharges for 1 h or more recovered their hydrophobicity faster than untouched specimens kept under identical conditions. X-ray photoelectron spectroscopy confirmed the early formation of a silica-like surface layer, with a thickness of at least 10–12 nm. The atomic composition of the oxidized surface layer remained essentially unchanged after the first hour of corona discharges. It is suggested that the silica-like surface layer delayed the recovery of hydrophobicity by inhibiting the transport of low molar mass PDMS to the surface. It is also suggested that thermally or purely mechanically induced stresses lead to a cracking of the brittle silica-rich layer and that this in turn facilitates the transport of low molar mass PDMS to the surface and to a more rapid recovery of the hydrophobicity. Data obtained by reflection infrared spectroscopy assessing the outermost micrometer, confirmed the oxidation and the formation of hydroxyl groups at a progressively higher concentration with increasing exposure time of corona discharges.

The sheets prepared by the extrusion of the melt of poly(butylene succinate) were treated with inorganic gas plasmas. Bionolle, the commercially available polyester, was also used, and the treatment effects were compared. Plasma susceptibility by the continuous plasma of 13.56 MHz and by pulsed plasmas was evaluated by the weight loss rates by etching. Advancing and receding contact angles of water (θa , θr ) on the plasma-treated sheets were obtained by the Wilhelmy method. Decay of hydrophilicity was considerable in θa , but θr was less changed. The biodegradation was examined by the preliminary soil-burial tests. The polymer sheets were biologically degraded, and the characteristic morphology appeared on the surface according to the SEM observation.

Extensive study has been made of the effects of various types of glow discharge plasmas on the changes of the surface properties of some fluorine polymers. The properties were investigated as a function of such factors as the exposing period, aging after exposure, type of plasma, and so on.

It was found that the wettability and the critical surface tensions were changed considerably with plasma exposure and that periods of several tens of seconds are long enough to cause changes. The extents of change were not so prominent for fluorine polymers as for polyethylene, and this fact may show the important role of the fluorine atom in the surface properties even after the plasma treatments.

The influence of substrate roughness on wettability has been investigated at room and high temperatures using sixteen material combinations, mostly liquid metals and solid ceramics but also water, glycerol and solid nickel. The contact angles assumed by both wetting and non-wetting drops of all but two material combinations increased linearly with the relative steepness of the surface features, the effect being less for experiments conducted at high temperatures. In contrast, the contact angles of good wetting drops of glycerol and exceptionally good wetting drops of Easy-flo decreased when their silica and nickel substrates were roughened. Similarly, contact angles of both wetting and non-wetting drops were decreased by ultrasonic vibration. The experimental data can best be interpreted in terms of the metastable equilibrium configuration models in which an advancing liquid front has to overcome energy barriers associated with surface features. This occurs more readily if these barriers are small relative to the energy of the liquid which our data suggest can be equated with the enthalpy of the liquid. This interpretation enables the effects of substrate roughness at one temperature or with one liquid to be used to predict behaviour at other temperatures and with other liquids.

The efficiency of different techniques of obtain improved adhesion in polyethylene-aluminum laminates have been studied. Both surface treatments, such as thermal oxidation and corona discharge, and the use of copolymers with polar comonomers, i.e., vinyl acetate (EVA) and butyl acrylate (EBA), have been included. Thermal oxidation performed by high temperature extrusion including an ozone shower seems to be more effective than corona discharge. In a model experiment thermal oxidation was studied in more detail. The adhesion, as measured by a T-peel test, increased with the content of carbonyl measured by reflexion IR, except for relatively long thermal treatments. In the latter case molecular scission gave a large fraction of low molecular weight material with low cohesive strength. For EBA and EVA the peel strength increased linearly with the bulk concentration of comonomer from about 100 N/m for untreated polyethylene to 450 and 300 N/m, respectively, at 5 mol % comonomer. Corona discharge treatment of these copolymers had, however, a most remarkable effect on the adhesion properties. The increases, relative to untreated EBA and EVA, were much more dramatic compared to polyethylene, e.g., three to four and less than two times, respectively. The higher values obtained with EBA are suggested to be due to the conversion of acrylate groups into carboxylic acid. In the case of EVA, loss of acetic acid might instead decrease the content of polar groups.

Polymers formed from plasma-polymerized methane were employed to modify the surface properties of silicone rubber membrane. Polymers were evaluated based on the energy input parameter W/FM, where W is the discharge power, F is the monomer flow rate, and M is the molecular weight of the monomer. Dealing with the characteristics of plasma polymerization and the deposited polymer film, the effect of pumping rate on deposition rate and the coating thickness, surface energy, and gas permeabilities of methane-plasma-polymer-coated silicone rubber membrane were investigated in three plasma regions. Because more reactive species are expelled at high pumping rates, the monomer-deficient region is reached at lower W/FM in the high pumping rate system than that in the low pumping rate system. The composite parameter W/FM had a strong influence on coating thickness, gas permeability, surface energy, and the polar component of the surface energy but little effect on its dispersion component. Examination of gas permeabilities indicated that coating thickness was another important controlling factor on the properties of plasma polymer.

A known relationship between heat of vaporisation, surface tension and molar volume applicable to spherical non-polar molecules is modified to apply also to linear molecules; the treatment involves calculation of molar surface areas corresponding to the appropriate “fully-packing” molecular shapes.

A linear relationship between the ratio cohesive energy density/surface tension and the reciprocal of molar volume is predicted for members of homologous series and demonstrated, with data for the n-paraffins.

This paper concerns the use of the low-pressure plasma process to confer an hydrophobic character to poly(acrylonitrile) films, without altering their bulk properties. Plasma based fluorination processes using saturated fluorine compounds such as CF₄, C₆F₁₄ and mixtures CF₄/H₂ were used. Such treated polyacrylonitrile films were characterized by XPS analysis, infrared (ATR) spectroscopy and contact angle measurements. The use of CF₄ led to the fluorination of the film surfaces. Indeed, XPS spectra showed the presence of -CHF-, -CF₂- and -CF₃ groups. Moreover, the contact angle θ which was 63° for untreated PAN films increased to 115°. Fluorine incorporation in the PAN disappeared when hydrogen is added to CF₄. In the case of treatment by C₆F₁₄, fluorination was accompanied by a polymerization, as evidenced by XPS with the disappearance of the N 1s photopeak corresponding to the C≡N functions in PAN. By considering the deposition of F- containing layer thickness, it was possible in this latter case to follow the surface modifications by ATR-i.r. spectroscopy