Ethylene-propylene diene monomer (EPDM) containing dicyclopentadiene (DCPD) and ethylidene norbornene (ENB) as the termonomers, styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR) have been surface-modified by 10% methyl ethyl ketone (MEK) solutions of trimethylol propane triacrylate (TMPTA) at an irradiation dose of 100 kGy. The irradiation dose and TMPTA concentration were optimized using samples treated with 2, 5, 10, 20, and 50% TMPTA and 50, 100, 200, and 500 kGy doses. Two per cent solutions of acrylate rubber having diene, chloro, and epoxy groups at the reactive sites and tripropyleneglycol diacrylate (TPGDA) and tetramethylol methane tetracrylate (TMMT) were also employed as the surface modifiers. The level and nature of the vulcanization system were varied. The modified rubbers were characterized by attenuated total reflection infrared (ATR-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. IR and XPS studies confirmed the generation of polar groups such as CO and COC on the surfaces. The contact angles and the surface energy change with the nature of the modifiers, rubbers, diene monomers, the crosslinking system and the level of the curing agent. The total surface energy and the thermodynamic work of adhesion of the different systems have been correlated with the amount and the nature of the polar groups generated.

The formation of the interface between aluminium and O₂ or CO₂ plasma-modified poly(ethylene terephthalate) (PET) has been investigated by X-ray photoelectron spectroscopy (XPS). As demonstrated by the changes in the C 1s, O 1s, and A1 2p core level spectra upon A1 deposition, the metal was found to react preferentially with the original ester, with the plasma-induced carboxyl and carbonyl groups to form interfacial complexes. The phenyl ring at the modified PET surface was seen to be involved in the formation of the interface, but to a lesser extent. This confirms the high reactivity of the oxygen-containing groups towards the deposited A1 atoms. The adhesion between A1 and the plasma-modified PET films was evaluated by means of a 180° peel test. A considerable (up to ten times) improvement in adhesion was achieved by plasma treatment of the PET substrate, but for either plasma gas the adhesion strength was found to depend strongly on the plasma power and treatment time. The results are discussed in terms of the concentration of oxygen-containing groups at the polymer surface, the surface topography, and the possible presence of low-molecular-weight materials at the metal-polymer interface.

The thin-layer wicking technique was used to determine the surface free energy components and the surface character of three celluloses (Sigmaccll 101, Sigmacell 20, and Avicel 101), using an appropriate form of the Washburn equation. For this purpose, the penetration rates of probe liquids into thin porous layers of the celluloses deposited onto horizontal glass plates were measured. It was found that the wicking was a reproducible process and that the thin-layer wicking technique could be used for the determination of the celluloses' surface free energy components. The size of the cellulose particles was characterized with the Galai CIS-100 system and their crystallinity was measured by X-ray diffraction. The three celluloses have high apolar (y^LWS = 50-56 mJ/m²) and electron donor (γs = 42-45 mJ/m²) components, while the electron acceptor component (γS⁺ ) is practically zero. The free energy interactions of cellulose/water/cellulose calculated from the components are positive, regardless of the cellulose crystallinity. This would mean that the cellulose surfaces have a hydrophilic character. However, the work of spreading of water has a small negative value (3-9 mJ/m²), indicating that the surfaces are slightly hydrophobic. It is believed that the work of spreading characterizes better the hydrophobicity of the surface than the free energy of particle/water/particle interaction, because in the latter case, no electrostatic repulsion is taken into account in the calculations.

FEP sheets were modified with a remote hydrogen plasma and the effects of the modification on the adhesion between copper metal and FEP sheets were investigated. The remote hydrogen plasma treatment is able to make FEP surfaces hydrophilic. In the remote hydrogen plasma treatment process, both defluorination and oxidation occur on the FEP surface. The oxidation reactions on the FEP surface form oxygen functional groups such as CO and CO groups. Modification of the FEP surface by the remote hydrogen plasma is effective in improving the adhesion of copper metal. The peel strength of the Cu/FEP system increased form 0 to 195 mN/5 mm, and the failure mode changed from the Cu metal/FEP polymer interface to within the FEP polymer layer. Remote hydrogen plasma treatment may be a preferable pretreatment of the FEP surface for adhesion with copper metal.

Axisymmetric adhesion tests are used to probe the adhesion between a carboxylated, poly(n-butyl acrylate) (PNBA) elastomer and a variety of substrates. The elastomer is in the form of a hemispherical cap, which is pressed against a flat substrate to give a circular contact area. A standard fracture mechanics approach is used to relate the applied load and the radius of the contact area to the energy release rate, 𝒢, which can be viewed as an adhesion energy. For a given substrate, 𝒢 is a function of the crack velocity, v, defined as the time derivative of the contact radius. The contact pressure does not appear to play a role in the development of the adhesive forces, and the specific relationship between 𝒢 and v depends on the substrate. In all cases this relationship can be adequately described by the empirical expression, 𝒢(v) = 𝒢₀(1 + (v/v*)^0.6). Values of 𝒢₀ are within a factor of about 2 of the expected thermodynamic work of adhesion, but values of v* vary from 5.5 to 215 nm/s, depending on the detailed nature of the substrate. Decreases in the adhesion energy, as quantified by a decrease in 𝒢₀ and/or an increase in v*, are determined primarily by the segmental mobility of the substrate molecules. Comparison of results for free and grafted PNBA chains indicates that translational diffusion of molecules at the substrate is not required in order to substantially reduce the adhesion energy.

The dependence of cell or bacteria adhesion and growth on the polarity of a polymer substrate, as controlled by the composition of a HEMA-EMA copolymer, has been studied by contact angle measurements. These have been analyzed by the acid/base hydrogen bonding methodology of van Oss, et al. It was found that adhesion and growth of mouse 3T3 cells occurred on surfaces for which the acidic parameter, γ^⊕_S, was negligibly small. This was the case above 50% EMA, for which γ^p was zero, and both attachment and growth occurred. The γ^⊕ parameter was appreciable, but approximately constant, independent of composition of the copolymer. The acid/base theory thus supplants the simple polar-nonpolar (γ^pandγ^d) hypothesisin regard to cell adhesion. A new 3-dimensional representation of hydrophilic/hydrophobic behavior is suggested, to implement the acid/base description.

Recent progress in the correlation of contact angles with solid surface tensions are summarized. The measurements of meaningful contact angles in terms of surface energetics are also discussed. It is shown that the apparent controversy with respect to measurement and interpretation of contact angles are due to the fact that some (or all) of the assumptions made in all energetic approaches [7–14] are violated when contact angles are measured and processed. For a large number of polar and non-polar liquids on different solid surfaces, the values of γ_1v cos θ are shown to depend only on γ_1v and γ_sv when the appropriate experimental techniques and procedures are used. An equation which follows these experimental patterns and which allows the determination of solid surface tensions from contact angles is discussed.

Plasma treatment is a common process for cleaning, etching and chemically functionalizing surfaces of polymer films. High speed plasma treatment is performed at atmospheric and subatmospheric pressure with a treatment device combining magnetic and hollow cathode effects, which enhance the gas ionization and focus and direct the plasma energy onto the surface of the moving web. Plasma treated polymer films show highly increased micro roughness. Polymer films metallized after plasma treatment exhibit highly improved adhesion between polymer and metal and better oxygen and water vapor barrier behaviour. Fabrics can be treated to attain hydrophilic or hydrophobic properties.

Recently, a glow like dielectric controlled barrier discharge (GDBD) working at atmospheric pressure has been observed. Such a discharge could replace a filamentary dielectric controlled barrier discharge (FDBD) used in corona treatment systems to improve the wettability or the adhesion of polymers. So it is of interest to compare these two types of discharges and their respective effect on a polymer surface. This is the aim of an extensive study we have undertaken. The first step presented here is the comparison of a filamentary discharge in air with a glow discharge in helium. Helium is the most appropriate gas to realize a glow discharge at atmospheric pressure. Air is the usual atmosphere for a corona treatment. The plasma was characterized by emission spectroscopy and current measurements. The surface transformations were indicated by the water contact angle, the leakage current measurement and the X-ray photoelectron spectroscopy. Results show that the helium GDBD is better than air FDBD to increase polypropylene wettability without decreasing the bulk electrical properties below a certain level. Contact angle scattering as well as leakage current measurements confirm that the GDBD clearly results in more reproducible and homogeneous treatment than the FDBD.

Recent progress in the correlation of contact angles with solid surface tensions are summarized. The measurements of meaningful contact angles in terms of surface energetics are also discussed. It is shown that the apparent controversy with respect to measurement and interpretation of contact angles are due to the fact that some (or all) of the assumptions made in all energetic approaches [7–14] are violated when contact angles are measured and processed. For a large number of polar and non-polar liquids on different solid surfaces, the values of γ _1v cos θ are shown to depend only on γ _1v and γ_sv when the appropriate experimental techniques and procedures are used. An equation which follows these experimental patterns and which allows the determination of solid surface tensions from contact angles is discussed.

Low-rate dynamic contact angles of 12 liquids on a poly(methyl methacrylate/n-butyl methacrylate) P(MMA/nBMA) copolymer are measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It is found that 6 liquids yield non-constant contact angles, and/or dissolve the polymer on contact. From the experimental contact angles of the remaining 6 liquids, it is found that the liquid- vapour surface tension times the cosine of the contact angle changes smoothly with the liquid-vapour surface tension, i.e., γ_iv cos θ depends only on γ_iv for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert and noninert (polar and non-polar) surfaces [34-42, 51 -53]. The solid-vapour surface tension calculated from the equation-of-state approach for solid -liquid interfacial tensions [14] is found to be 34.4 mJ/m², with a 95% confidence limit of \pm 0.8mJ/m², from the experimental contact angles of the 6 liquids.

Low-rate dynamic contact angles of 22 liquids on a poly(n-butyl methacrylate) (PnBMA) polymer are measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It is found that 16 liquids yielded non-constant contact angles, and/or dissolved the polymer on contact. From the experimental contact angles of the remaining 6 liquids, it is found that the liquid–vapor surface tension times cosine of the contact angle changes smoothly with the liquid–vapor surface tension, i.e. γ_lv cos θ depends only on γ_lv for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert and non-inert (polar and non-polar) surfaces [34–37, 45–47]. The solid–vapor surface tension calculated from the equation-of-state approach for solid-liquid interfacial tensions [14] is found to be 28.8 mJ/m², with a 95% confidence limit of ±0.5 mJ/m², from the experimental contact angles of the 6 liquids.

Low-rate dynamic contact angles of 13 liquids on a polystyrene polymer are measured by an automated axisymmetric drop shape analysis – profile (ADSA-P). It is found that 7 liquids yielded non-constant contact angles, and/or dissolved the polymer on contact. From the experimental contact angles of the other 6 liquids, it is found that the liquid-vapor surface tension times cosine of the contact angle changes smoothly with the liquid-vapor surface tension, i.e. γ_lvcosθ depends only on γ_lv for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert and non-inert (polar and non-polar) surfaces (7–13, 24–26). The solid-vapor surface tension calculated from the equation-of-state approach for solid-liquid interfacial tensions (33) is found to be 29.8 mJ/m², with a 95% confidence limit of ±0.5 mJ/m² from the experimental contact angles of 6 liquids.

Low-rate dynamic contact angles of nine liquids on a poly(methyl methacrylate) (PMMA) polymer are measured by an automated axisymmetric drop shape analysis—profile (ADSA-P). It is found that two liquids dissolved the polymer on contact. From the experimental contact angles of the other seven polar and nonpolar liquids, it is found that the liquid–vapor surface tension times cosine of the contact angle changes smoothly with the liquid–vapor surface tension (i.e., γ_lνcos θ depends only on γ_lνfor a given solid surface). The dependence of γ_lνcos θ on γ_sνis explicitly illustrated by replacing the solid surface from the PMMA to other methacrylate polymers: such a procedure shifts the curves in a very regular manner. Thus, because of Young's equation, γ_sldepends only on γ_lνand γ_sν. This contact angle pattern is in harmony with those from other inert and noninert (polar and nonpolar) surfaces. The solid–vapor surface tension of PMMA calculated from the equation of state approach for solid–liquid interfacial tensions is found to be 38.5 mJ/m², with a 95% confidence limit of ±0.5 mJ/m²from the experimental contact angles of the seven liquids.

Low-rate dynamic contact angles of water, glycerol and methylene iodide on polystyrene and poly(4-(X = CH₃, (CH₃)₃, Cl, OH)-styrene) films were measured by axisymmetric drop shape analysis-profile (ADSA-P) for sessile drops. It was found that glycerol in the case of poly(4-chlorostyrene) and methylene iodide on all investigated surfaces did not yield constant contact angles: dissolving of the polymer during the contact with the liquid, penetration effects and stick/slip behavior were found. Water and glycerol yielded meaningful constant contact angles (except for glycerol on poly(4-chlorostyrene), for which we used formamide additionally). From these meaningful contact angles the solid surface tensions of the modified polymers were calculated using the equation of state approach [6]. The following values of γ_sv were determined: polystyrene γ_sv = 28.3 mJ/m², poly(4-methylstyrene) γ_sv = 25.8 mJ/m², poly(4-tert-butylstyrene) γ_sv = 22.0 mJ/m², poly(4-hydroxystyrene) γ_sv = 44.1 mJ/m², poly(4-chlorostyrene) γ_sv = 27.2 mJ/m².

It is shown that Axisymmetric Drop Shape Analysis (ADSA) is well-suited for the study of polymer melt surface tensions. The technique is not restricted to equilibrium surface (interfacial) tensions; it is also suitable for measuring the time dependence (or kinetics) of surface tension of polymer melts. Results for three polymers, polypropylene, polyethylene, and polystyrene, at temperatures above 170°C are reported. Contrary to the well-known decrease of surface tension in low molecular weight surfactant solutions as a result of equilibration, an increase in the melt surface tension is observed under isothermal conditions.

Low-rate dynamic contact angles of 30 liquids on a FC-725-coated wafer surface were measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). Surprisingly, results indicate that FC-725 behaves differently in some respects from what one would expect for non-polar surfaces: only nine liquids yield essentially constant contact angles whereas the others show slip/stick contact angle behaviour. In the worst case, the contact angle increases from ca 50 to 160° at essentially constant three-phase contact radius. These angles should be disregarded for the interpretation in terms of surface energetics since there is no guarantee that Young's equation is applicable. If one employs a conventional goniometer-sessile drop technique, such contact angle behaviour cannot be easily seen in all cases. These results indicate that the claim from van Oss et al. [Langmuir 4 (1988) 884] that liquids with the same contact angles do not have the same surface tensions is misleading. If the meaningful contact angles are plotted as the liquid–vapour surface tension times cosine of the contact angle versus the liquid–vapour surface tension, that is, γ_lv cos θ versus γ_lv, a smooth curve emerges. Thus, intermolecular forces (or surface tension components) do not have an additional and independent effect on the contact angles, in good agreement with the results from other studies on non-polar and polar polymers.

Positive and negative dc corona discharges in CO-air and -air mixtures were applied. Natural humid air was used. The step by step development with time of the formation of gas products after the action of the corona discharge was measured in situ. The discharge tube was situated in an IR gas cell. The IR absorption spectra were scanned from the area of the inter-electrode distance in successive time steps of the action of the discharge (about 1 min). Measurements were performed for three combinations of electrode materials, namely Mo-stainless steel, Mo-brass and Cu-brass. Reflection IR absorption spectra from the surfaces of the electrodes used were scanned after the action of the discharge. The influence of the electrode material on the development with time of the reaction products was observed. Polymer-metal complexes with possible catalytic activity are formed on the surfaces of electrodes. From measurements it resulted that the discharge processes consist of simultaneously acting volume processes of plasmochemical nature (probably initiated by electrons) and electrocatalytic surface processes on electrodes (probably initiated by photons).

The surface modification of high density polyethylene (HDPE) and polypropylene (PP) has been carried out by exposure to a DC glow discharge in air at different power levels of 5.28, 11, and 13 W. The surface energies of polymers exposed to glow discharge were estimated by measuring the contact angles of two test liquids: de-ionized water and formamide, whose surface energy components are known. Both the polar and the dispersion components of the surface energy increased rapidly at short exposure times but the increase of the polar component was relatively more than that of the dispersion component. At low power levels of 5.28 and 11 W, the polar component of the surface energy reached a maximum plateau depending on the exposure time, but at a 13 W power level the polar component of the surface energy decreased from a maximum value to a saturation level. For PP, this saturation level could not be attained in this study. The maximum total surface energy measured in this study corresponds to the maximum polar component at 13 W for an exposure time of 120 s. The contact angle of the adhesive, Araldite AY 105 mixed with hardener HY 840 in a weight ratio of 2 : 1, was minimum at this maximum surface energy attained with HDPE and PP by exposure to a glow discharge in air. The measured lap shear strengths of HDPE or PP-Araldite-mild steel joints show a maximum corresponding to the maximum surface energy measured on the above-mentioned polymers.

In the present work, rubber-toughened polypropylenes (TPOs) with different properties of the rubbery phase, consisting in different degrees of rubber dispersion and different levels of rubber crystallinity, were considered. The flame-treated surfaces of these materials and their interfaces with a commonly used primer were studied by dynamic contact angle (DCA) analysis using seven liquids and by scanning probe microscopy (SPM). The contact angle data were analysed using the concepts and the equations of the surface free energy acid-base component theory. A new approach consisting in the use of a large number of probe liquids and of a proper mathematical method is proposed; it allows higher precision in the determination of the surface energy components and the work of adhesion, the reduction of possible artefacts, and the calculation of standard deviations of obtained quantities. It was found that: (i) the characteristics of the flame-treated surfaces were largely independent of the composition and morphology of the rubbery dispersed phase; (ii) the flaming effect was better shown by receding angles and the observed hysteresis allowed a quantitative evaluation of the surface heterogeneity induced by the flame process; and (iii) the flame treatment induced fragmentation of the macromolecules with the production of fragments, soluble in all the test liquids, depending on their surface tension and their acid-base character, as shown by repeated DCA immersions. A comparison has been made with the ASTM 2578-67 method ('swab'). The SPM analysis, both in contact and in 'force spectroscopy' modes, confirmed the surface model obtained by the DCA data.

The surface free energy of polymeric films of polyvinylchloride (PVC) + poly(ethylene-co-vinylacetate) (EVA) blends was calculated using the van Oss treatment (Lifshitz and electron donor–electron acceptor components of surface free energy) and the Owens–Wendt treatment (dispersive and nondispersive components of surface free energy). Surface free energy results were found to be greatly dependent on the calculation method and on the number of standard liquids used for contact angle measurements. The nondispersive/donor–acceptor surface free energy component and the total surface free energy of polymeric films were always higher when the van Oss treatment was used compared to the Owens–Wendt treatment. Conversely, both methods led to similar apolar/Lifshitz components. All the calculation methods were in good agreement for the surface free energy of PVC; however, a discrepancy between the methods arose as EVA content in the blends increased. It seems that there is not yet a definite solution for the calculation of solid surface free energy. Further developments of existing models are needed in order to gain consistency when calculating this important physicochemical quantity.

The physicochemical modifications of ammonia-treated polypropylene (PP) films have been studied and characterized in terms of acid-b ase properties using the contact angle titration method and X-ray photoelectron spectroscopy in conjunction with a molecular probe technique using chloroform as a reference Lewis acid. These techniques have shown that PP surfaces that have been treated for between 0.7-1 s are basic in character. For longer treatment times, the basic character of the surfaces decreases, as shown by the above techniques and confirmed by time of flight-secondary ion mass spectroscopy (ToF-S IMS). On the other hand, for such treatment times, a degradation of the adhesion and mechanical properties was observed. The ageing of an ammonia-plasma-treated PP was limited by a helium (He) plasma pretreatment known to crosslink the surface, stabilizing in this way the wettability, adhesion and mechanical properties. ToF-S IMS was performed on helium treated High Density Polyethylene (HDPE) in order to point out the structural modifications.

We discuss plasma surface modifications applied to perfluorinated polymers and polyolefins to achieve structural adhesive bonding or for biomedical purposes such as adhesion and proliferation of cells, and interfacial immobilization of biologically active molecules. We compare the properties of surface modifications performed in non-depositing plasma treatments with those of thin coatings produced in depositing plasma vapours (plasma polymerization), with particular emphasis on changes, on subsequent storage, to the properties and composition of the surface layers (‘ageing’). Such changes usually proceed for extended periods of time after plasma processing. Polymer surfaces treated in non-depositing plasmas generally are unstable, showing an increase in the air/water contact angles over days and weeks due to surface reorientation motions. Concurrently, the composition of the surface layers is also affected by post-plasma chemical reactions: originating from trapped radicals, oxidative chain reactions lead to the production of substantial amounts of oxygen-containing groups. These reactions also convert some of the groups originally incorporated into the surface layers by the plasma treatment; for instance, amine groups are converted to amide groups as evidenced by shifts in the XPS N 1s binding energy. Plasma polymer coatings analogously undergo oxidative compositional changes with time, and are capable of some surface reorganization. Thus, the nature and densities of the chemical groups on plasma-treated surfaces and plasma polymer coatings can change considerably with time. The relative contributions by concurrent reorientation motions and oxidative reactions to the compositional changes vary markedly between different plasma-prepared surfaces, but usually both processes contribute to the ageing of a surface. The generally long time constants of the reorientation of plasma polymer surfaces suggest that their limited, slow mobility may be neglected when interpreting interactions with adsorbing proteins.

Injection-moulded plates of four commercial thermoplastic polyolefins (TPOs) were subjected to oxygen plasma treatment. The modified surfaces were analyzed by water contact angle measurements and X-ray photoelectron spectroscopy (XPS), and the adhesion properties of the plates were evaluated by a 90 peel test after being lacquered with a two-component polyurethane lacquer. The study included treatments in two different plasma reactors operating at different frequencies. The influence of certain processing parameters, such as discharge power, flow rate and gas pressure, was investigated, as was that of frequency (using the same reactor). While the results revealed that oxygen plasma treatment indeed led to improved wettability, the degree of surface modification was not highly affected by changes in the processing conditions. In contrast, there was a great effect on the lacquer adhesion, in particular by changes in discharge power and gas pressure. The results also showed that the TPOs were sensitive in different ways towards changes in the processing conditions. It was also found that, regardless of the absolute peel force, the failures occurred in the substrate at some distance below the oxidized layer. These observations were attributed to a VUV-induced formation of radicals which, in the case of polypropylenebased materials, predominantly lead to^-scissions. As secondary radicals have a higher tendency to form crosslinks that can compensate for chain scission reactions, the difference in the sensitivity of the TPOs was proposed to be related to the amount and distribution of ethylene in the materials.

The most effective commercial methods for pretreating fully fluorinated polymers at present are sodium in liquid ammonia and sodium naphthalenide in a solvent such as tetrahydrofuran. A number of other methods can produce large increases in bondability but are relatively inefficient. Plasma treatments of fully fluorinated polymers such as PTFE often introduce functional groups and/or increase wettability but result in moderate improvements at best in bondability. However, recent work with ammonia plasmas has resulted in big improvements in bondability. Some batches of partially fluorinated polymers may be effectively bonded without a pretreatment. However, other batches possess surface regions of low cohesive strength. Partially fluorinated polymers such as poly (vinyl fluoride) may be rapidly and effectively treated with a conventional flame treatment. Where a flame treatment is unsuitable, as with complex shapes, potassium hydroxide solutions provide effective treatments for partially fluorinated polymers such as poly (vinyl fluoride) and poly (vinylidene fluoride).

The Harkins relationship, that the spreading coefficient of an adhesive on a release coating is the difference between the work of adhesion of the materials and the work of cohesion of the adhesive, has been found to apply to a variety of silicone release coatings. The works of adhesion and cohesion were estimated from contact angle data using the Owens and Wendt approach. The prediction of the Harkins relationship is obeyed by almost all the combinations of pressure-sensitive adhesive and release coatings we have examined. Release occurs when the spreading coefficient is negative and does not when it is positive. The main exception to this general spreading coefficient rule is the failure of polytetrafluoroethylene to release polydimethylsiloxane-based pressure-sensitive adhesives. The cause is believed to be roughness of the polytetrafluoroethylene surface.

Many wetting processes involve interpretation using Young’s equation to describe contact angle equilibrium on a solid surface. By assuming the solid to be rigid, no account is made of the component of the liquid surface tension perpendicular to the solid surface. It is shown that a wetting ridge must be formed and, although negligible for hard solids, this mesoscopic disturbance of the solid near the wetting front can have significant consequences on a soft solid. The theory of triple line displacement, taking into account viscoelastic dissipation in the wetting ridge, is developed both for wetting and dewetting processes. Experimental studies using tricresyl phosphate and two types of model solid—a rigid polymer and silicone elastomers—have been carried out. Both for wetting and dewetting, triple line motion is markedly slowed down on the soft solids as a result of viscoelastic dissipation near the triple line. Theoretical predictions and experimental findings are found to be in good agreement.

Contact angle hysteresis on rough surfaces is caused by the contortion of the liquid surface that must occur as the liquid front passes from one metastable configuration to another. We have combined the Wenzel equation for the effect of roughness on the contact angle, 0, with the well-known equation relating contact angles to the surface free energy of the solid and of the liquid, and with Good’s hypothesis of a free energy barrier to liquid front motion. The method that is developed calls for measuring 0 for a series of liquids and plotting cos0a vs./yi and extrapolating to the limit of (\/yi) 0. On a perfectly smooth, homogeneous surface, the intercept is—1 and the Wenzel ratio for a rough surface is given, approximately, by the negative of the value of the intercept. A shift of the yc value for the solid, due to roughness, is also predicted. Experimental data are presented for measurements with Teflon FEP.

The activation of polymer surfaces in glow discharges and the deposition of metals from organo-metallic vapours, both at low pressure, are standard laboratory processes. The upscaling to industrial mass product applications is, however, hampered by cost and the time consumption needed for establishing a sufficient vacuum. Atmospheric pressure processes based on the same physical surface interactions show great promise as replacements of some steps in galvanic plating. Successful metallizations are reported after treatment of polymers in barrier discharges at atmospheric pressure. These may be applied directly to the surface of the workpiece or indirectly from within large-area monochromatic excimer UV lamps. Comparisons with excimer UV laser treatment are made.

For vacuum web coating for permeation barrier coatings in flexible packaging, the final functionality of the packaging media is extremely dependent on the whole chain of processing steps up to the final laminated packaging film. The most sensitive sector appears to be, on the one hand the hand-shake between substrate film pretreatment–substrate surface properties and the coating process with its characteristics on the other. The influence of different surface pretreatment processes (Corona activation, oxygen and ammonia plasma treatment) on active surface groups of BOPP (biaxial-orientated polypropylene) substrates is shown together with: (1) specifities of the thermal deposition (electron beam source); (2) the reactive deposition–microwave plasma process (plasma species, excitation characteristics, kinetic energies, obtained by in situ process monitoring); and (3) structural properties (chemical composition, adhesion and oxygen permeation) of the thin barrier films (Al₂O₃ and SiO_x), in correlation with the achieved functional properties of the barrier coated films.

This paper considers the correctness of the application of Good–van Oss theory (vOGT) to the calculation of acid–base components of solid surface free energies. Theory equations are written in a matrix form, and their application is analyzed particularly from a mathematical point of view. A calculation procedure similar to the approach used for other scales of acid–base strength is suggested to obtain in a straightforward manner the necessary material coefficients. The chemical consequences of these considerations are also discussed. The acceptability of current experimental literature data and the validity of the calculations obtained from them by the proposed method are considered, showing the origin of some inconsistencies in current results. Some general considerations regarding the difficulties commonly encountered in the application of vOGT are also discussed, and it is shown that they can be rationalized or eliminated with more acid solvents being included in the solvent set and the properties of the reference solvent being correctly chosen. The difficulties encountered in correctly expressing the acid properties of some polymers are closely examined. Finally, some indications are given of the future possible developments of vOGT.

Polymer films of poly(ethylene terephthalate), polypropylene, and cellophane were surface treated with tetrafluoromethane plasma under different time, power, and pressure conditions. Contact angles for water and methylene iodide and surface energy were analyzed with a dynamic contact angle analyzer. The stability of the treated surfaces was investigated by washing them with water or acetone, followed by contact angle measurements. The plasma treatments decreased the surface energies to 2–20 mJ/m² and consequently enhanced the hydrophobicity and oleophobicity of the materials. The treated surfaces were only moderately affected after washing with water and acetone, indicating stable surface treatments. The chemical composition of the material surfaces was analyzed with X-ray photoelectron spectroscopy (XPS) and revealed the incorporation of about 35–60 atomic % fluorine atoms in the surfaces after the treatments. The relative chemical composition of the C ls spectra's showed the incorporation of —CHF— groups and highly nonpolar —CF₂— and —CF₃ groups in the surfaces and also —CH₂—CF₂— groups in the surface of polypropylene. The hydrophobicity and oleophobicity improved with increased content of nonpolar —CF₂—, —CF₃, and —CH₂—CF₂— groups in the surfaces. For polyester and polypropylene, all major changes in chemical composition, advancing contact angle, and surface energy are attained after plasma treatment for one minute, while longer treatment time is required for cellophane. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1591–1601, 1997
https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1097-4628(19971121)66:8%3C1591::AID-APP21%3E3.0.CO;2-5