In this paper, several acrylic pressure-sensitive adhesives (PSAs) were studied through adhesion tension relaxation (ATR) technique introduced by Kasemura and Takahashi. These acrylic PSA samples were also analyzed through static contact angle, surface free energy, dynamic contact angle hysteresis, and peel force measurements. The study has shown that the acrylic PSAs are multicomponent polymeric systems which reorient their surface segments so as to minimize interfacial tension in response to environmental changes. Therefore, it is important to consider the mobility of the surface segments of PSAs in understanding their contact angle hysteresis. Further, the ATR technique has proven to be useful in estimating such mobility.

Tbe relationship of contact angles to surface structure is outlined. The difference between the advancing and receding contact angles is discussed in terms of the modern theory of multimolecular adsorption; this theory indicates that the advancing angle will be unique, whilst the receding one will generally be less than the advancing angle and need not have a unique value.

This paper follows the “defense” of the Good-van Oss-Chaudhury (GvOC) acid-base approach made in Part I and carries out a detailed analysis of the Zisman critical surface energy and, mainly, of the Neumann equation-of-state (EQS) theory. The analysis is made on both a “practical” and a theoretical basis, trying to highlight the acceptable fitting results of axisymmetric drop shape analysis (ADSA) methods and their independence of the assumed thermodynamic foundations of EQS. Some new and original criticisms of the EQS approach are raised and it is shown that other purely semiempirical models, represented by different fitting equations with the same number of parameters, can represent the data measured by ADSA method with the same goodness as EQS. The equation of state appears as one of many semiempirical approaches for the evaluation of surface free energy of solids. Independent of the previous analysis, the criteria used in ADSA measurements are evaluated and some comments made on them.

Atmospheric pressure plasma treatment of the surface of a polypropylene film can significantly increase its surface energy and, thereby improve the printability of the film. A laboratory-scale dielectric barrier discharge (DBD) system has therefore been developed, which simulates the electrode configuration and reel-to-reel web transport mechanism used in a typical industrial-scale system. By treating the polypropylene in a nitrogen discharge, we have shown that the water contact angle could be reduced by as much as 40° compared to the untreated film, corresponding to an increase in surface energy of 14 mNm⁻¹. Ink pull-off tests showed that the DBD plasma treatment resulted in excellent adhesion of solvent-based inks to the polypropylene film.

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

Transmission electron microscopy and X-ray photoelectron spectroscopy (XPS) were used to characterise thin metal films (Mg, Al, Cu, Ag) thermally evaporated onto polyethylene terephthalate (PET) and to study the formation of the Al/PET interface. The adhesion was measured with a 180° peel test technique. XPS spectra show that the Al atoms react preferentially with the carboxylic group of the PET and that the Al/PET interface exhibits a pseudo layer-by-layer growth mechanism. Two factors strongly favour the increase of metal/PET adhesion: (1) a PET temperature higher than 100°C during metal deposition (Al, Cu and Ag) and (2) a partial pressure of oxygen higher than 10⁻⁵ mbar for the Al evaporation. Furthermore, atomic metal diffusion tends to increase the adhesion while cluster segregation within the PET skin decreases the metal/PET adhesion.

Preliminary results are presented on hydrophilization, grafting, and metal plating of PP nonwovens using novel types of atmospheric-pressure low-temperature plasma sources, namely the "Surface Discharge Induced Plasma Chemical Processing" source and the plasma source based on a coplanar diffuse surface discharge. The plasma sources generate a thin (~ 0.3 mm) surface layer of plasma and are capable of meeting the basic on-line production requirements for surface activation and permanent hydrophilization of light-weight nonwovens.

The surface of high-performance poly(ethylene terephthalate) (PET) fibers is difficult to wet and impossible to chemically bond to different matrices. Sizing applied on the fiber surface usually improves fiber wetting, but prevents good adhesion between a matrix and the fiber surface. The present study demonstrates that the plasma treatment performed by Surface dielectric barrier discharge (Surface DBD) can lead to improved adhesion between sized PET fabric and polyurethane (PU) or poly(vinyl chloride) (PVC) coatings. Moreover, it points out that this plasma treatment can outperform current state-of-the-art adhesion-promoting treatment. Plasma treatment of sized fabric was carried out in various gaseous atmospheres, namely N₂, N₂ + H₂O, N₂ + AAc (acrylic acid) and CO₂. The adhesion was assessed by a peel test, while wettability was evaluated using strike-through time and wicking rate tests. Changes in fiber surface morphology and chemical composition were determined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. Only the CO₂ plasma treatment resulted in improved adhesion. As indicated by the analyses, increased surface roughness and the incorporation of specific oxygen-containing groups were responsible for enhanced adhesion. The results presented were obtained using a plasma reactor suitable only for batch-wise treatment. As continuous treatment is expected to provide higher homogeneity and, therefore, even better adhesion, a scaled-up Surface DBD plasma system allowing continuous treatment is presented as well.

The primary goal of surface modification of fluoropolymers is to improve adhesion to these low surface energy materials. Both classical methods and newer processes have been used as a means to this end. Various methods of modifying fluoropolymer surfaces include wet chemical etching, electrochemical reduction, grafting, application and removal of metals, ion and electron beam techniques, and plasma modification. In addition to the modification procedure, it is necessary to evaluate the effectiveness of the chosen method by subsequent analysis of the modified surface. Physical analytical methods include contact angle and wettability measurements, lap shear and composite tensile shear strengths, peel strengths, and surface topographical determinations. Chemical analyses used include infrared, Raman, Rutherford backscattering, ultraviolet-visible, wide angle X-ray scattering, X-ray fluorescence, and X-ray photoelectron spectroscopies as well as thermal desorption mass spectrometry. Each of the modification methods, with results of the subsequent chemical or physical analysis, will be discussed.

An atmospheric pressure glow discharge (APGD) was used for surface modification of polyethylene (PE) and polypropylene (PP). The discharge was generated between two planar metal electrodes, with the top electrode covered by a glass and the bottom electrode covered by the treated polymer sample. The discharge burned in pure nitrogen or in nitrogen-hydrogen or nitrogen-ammonia mixtures. The surface properties of both treated and untreated polymers were characterized by scanning electron microscopy, atomic force microscopy, surface free energy measurements and x-ray photoelectron spectroscopy. The influence of treatment time and power input to the discharge on the surface properties of the polymers was studied. The ageing of the treated samples was investigated as well. The surface of polymers treated in an APGD was homogeneous and it had less roughness in comparison with polymer surfaces treated in a filamentary discharge. The surface free energy of treated PE obtained under optimum conditions was 54 mJ m^-2 and the corresponding contact angle of water was 40° the surface free energy of treated PP obtained under optimum conditions was 53 mJ m^-2 and the contact angle of water 42°. The maximum decrease in the surface free energy during the ageing was about 10%.