The effect of velocity upon the advancing and receding contact angles of water, glycerol, formamide and methylene iodide on glass coated with a dimethyl siloxane layer has been investigated. The cosines of the dynamic contact angles of water and glycerol vary linearly with the interfacial velocity, as predicted by hydrodynamic theory. However, this treatment cannot account for the magnitudes of the velocity effects observed with water and glycerol. Qualitative molecular considerations explain certain features of the velocity dependence of advancing contact angles. Initial rapid relaxation of the contact angles occurs on removal of the drive because of molecular reorientation of liquid molecules at the solid interface. There are further slow changes of water and methylene iodide advancing contact angles with time because of penetration of liquid changing the solid-liquid interfacial tensions. No penetration occurs with glycerol and formamide because of their greater effective molar volumes and with the former liquid the advancing and receding angles relax to a common value of about 90° which is considered to be the equilibrium value.

ESCA and contact angle measurements have been combined in a detailed study of the effect of surface-to-volume ratio or thickness on the surface composition of coatings of a mixture of two fluoroalkyl methacrylate polymers which differ in the length of their fluoroalkyl side chains. These measurements show that the polymer component with the longer side chain is surface active in the mixture. The surface concentration of this component was found to decrease with increasing surfaceto-volume ratio of the coating.

The paper describes an experimental investigation of the possibility of industrial modification of surface wettability and adhesion of polymers by the action of a plasma of a gliding discharge generated in air at atmospheric pressure in a simulated production process. The test material was polypropylene plates (PP). The modification was performed by a device with a multi-electrode (four pairs) system, which is not common. The quality of pre-processing and usability was evaluated primarily in terms of the industrial requirements, which means a change in wettability and adhesion expressed by the contact angle/surface free energy value in dependence to sample exposure time expressed by the conveyor belt speed. The surface free energy assessment of a treated polymeric surface by contact angle measurement was carried out by analyzing static sessile drops and evaluated by Owens–Wendt–Rabel–Kaelble (OWRK) model. The results determined a set of operating parameters at which the modification process meets the industrial requirements. By evaluating the change in surface free energy in relation to the storage time, the degree of hydrophobic recovery of the treated samples, i.e. the time stability of the plasma-treated surface, was also determined. It has been found that plasma-treated PP surface fully meets industrial demands and can be stored for at least 50 days.

The surface modification of polyethylene powder using a plasma reactor based on a dielectric barrier discharge in air at atmospheric pressure and ambient temperature is investigated. The process is inexpensive, and the necessity of any vacuum equipment and technical gases is alleviated. The efficiency of the modification process was successfully demonstrated by ESCA measurements that proved formation of new functional groups at the modified powder surface. The modification effect was also evaluated by means of dynamic capillarity rising measurements. Powder capillarity tests proved significant powder capillarity changes. The reduction of the modification effect was also limited (max. reduction of about 20% during 1 100 d after the modification date).

In a number of automotive applications of polypropylene (PP) good paint adhesion is essential. For industrial applications, the initially poor adhesion properties of PP compounds are often improved by flame treatment, resulting in good paint adhesion on the PP parts. For control purposes, intensive and time consuming paint tests are required. To relate adhesion behaviour with the parameters used in the flame treatment modification, several methods are applied such as simple surface tension tests with inks (wetting tests), contact angle measurements and standard XPS(ESCA) measurements. Unfortunately a good correlation is rarely obtained between these tests and the desired adhesion behaviour under rigid test conditions. Good wetting, for example, is necessary, but is no guarantee for good adhesion. In this paper results are presented on the characterisation of flame treated PP compounds by XPS, as well as the predictive information obtained from the XPS study concerning the paint adhesion behaviour of the modified PP surfaces.

By now, the effect of microorganisms on polymer materials has been well studied. However, most of the investigations were aimed at polymer protection against biocorrosion or, on the contrary, biodegradation of polymer wastes. Using microbial treatment for polymer adhesion improvement was initiated only in the past decade. Nevertheless, such treatment, being a variant of chemical surface modification, has a number of advantages in comparison with other known treatment techniques: It needs no expensive chemicals and solvents. It is conducted at moderate temperatures and needs no energy expenditure. It is ecologically clean. Because of the great variety of existing microorganisms, it can offer the desired degree of treatment for different polymer materials.

The critical surface tension of wetting (γ_c) for certain branched-chain polymeric fluoroalkyl acrylates and methacrylates was obtained. Polymeric materials utilized in this study can be represented by the repeating units

The wetting properties of a series of polyacrylates containing the fluoroalkyl group have been studied. Where n is 7 and 9, the polyacrylates are highly crystalline at room temperature. Since the polymers were prepared under atactic free-radical conditions and the polyacrylates with shorter alkyl groups (where n is 3 or 5) were not crystalline at room temperature, the crystallinity is presumed to occur as a result of side-chain packing and not involve the backbone. The polymers become more wet-table (higher γ_c) as polymer crystallinity was reduced by quenching or heating past T_m. Correlations have been made between the work of Zisman and co-workers on the wetting properties of various fluorinated acid monolayers and the wetting properties of these fluoroalkyl acrylates. The results obtained in this study concerning the influence of polymer crystallinity on surface wetting are discussed in relation to the findings of Schonhorn and Ryan on the wettability of polyethylene single crystal aggregates.

Gas-phase derivatization has been used along with e.s.c.a. to determine corona-discharge-induced chemical species on poly(ethylene terephthalate) (PET). Dry-air and dry-nitrogen coronas were studied. We showed that: (1) if the corona discharge treatment (CDT) power level is kept low enough, few water-soluble species are created; (2) 4% of oxygen is added to the surface with dry-air corona; (3) 75% of the oxidation products are identified as hydroperoxy, epoxy, hydroxyl, carboxylic acid and isolated carbonyl species (with hydroxyl and isolated carbonyl the prevalent species). Short-term time-dependent ageing studies show a one-to-one correspondence between the decrease in hydroperoxy species and the increase in hydroxyl and isolated carbonyl moieties. Reaction sequences are proposed to explain these data. At longer times these surface populations decrease. In general, the results from nitrogen coronas and dry-air coronas are similar.

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.

Water-based ink and coating use is reviewed with the emphasis on wetting and printing of film, metal, and metallized substrates. This paper addresses the effects of surface tension of water-based flexographic and rotogravure inks and coatings. The mode of drying in water-based technology is explored as well as static and dynamic surface tension of inks and coatings. Ink formulation and manufacturing considerations are reviewed to optimize surface tension effects for high speed presses. The role of substrate and ink transfer mediums are discussed relative to their impact on ink and coating drying rates. Corona treatment of film substrates is analyzed from the perspective of its effect on drying speed and ink adhesion. Suggestions are made to improve the quality performance of water-based ink and coatings through use of on-line surface tension equipment. Most importantly, the question “Why should I measure surface tension of my water-based ink?” is answered from the perspective of improving press productivity and ink performance.