Treatment of fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) in ammonia plasmas produced surfaces with very high wettability by water, but on storage in air at ambient temperature, the air/water contact angles increased markedly. The evolution of the surface composition and topography was studied by angle-dependent X-ray photoelectron spectroscopy (XPS), derivatization of amine groups with fluorescein isothiocyanate, scanning tunelling microscopy (STM), and atomic force microscopy (AFM). XPS demonstrated a continuous increase in the oxygen content over periods of weeks; this was assigned to oxidation of trapped radicals and subsequent secondary reactions. In addition, the fluorine content also changed markedly on storage; the XPS fluorine signal suggested that there was a substantial amount of fluoride in the freshly treated surfaces, and this component disappeared rapidly on storage. STM and AFM showed no changes in topography with aging but suggested surface hardening on plasma treatment. The events following treatment of FEP and PTFE in ammonia plasmas are not adequately described by a model involving plasma-induced, instantaneous chemical modification followed by surface restructuring; the surface and sub-surface compositions evolve over a period of several weeks due to the occurrence of oxidative reactions, and these chemical changes interact with the physical process of surface restructuring.

The effect of a variety of wetting liquids on the resistance to peeling separation for a lightly crosslinked rubbery adhesive in contact with a Mylar substrate has been studied over a wide range of peeling rates and at two temperatures. Although the magnitude of the peel strength is much greater than the thermodynamic work of detachment, it is reduced by alcohols and alcohol/water mixtures in good agreement with calculated reduction factors. It is concluded that the measured strength is a product of two terms: the thermodynamic work, and a numerical factor, generally large, denoting inefficiency. The latter term is strongly dependent on peel rate and temperature for viscoelastic adhesives. Two anomalies are pointed out: particularly low adhesion is observed at low rates of peel for certain liquids, attributed to swelling of the adhesive, and smaller effects are found for some other liquids than predicted.

X-Ray photoelectron spectroscopy (XPS) was used to determine plasma induced chemical species on the surface of polyethylene (PE). Argon plasmas were found to have no detectable chemical effect on the PE surface, whereas oxygen and nitrogen plasmas created new chemical species which altered the chemical reactivity of the PE surface. Oxygen plasmas were found to react more rapidly with the PE surface than nitrogen plasmas. The degree of incorporation of new chemical species in the near surface region is approximately 20 at. % at the saturation level for both oxygen and nitrogen plasmas. Core level spectra for oxygen and nitrogen plasma treated PE suggest the formation of primarily C-O-C species in the former and C-N species in the latter. Angle-resolved XPS measurements indicate that the depth of incorporation of new chemical species is confined to the top 25 A.

Chemically specific gas-phase reactions have been used to tag corona-discharge-induced chemical species on the surface of polyethylene. These tag reactions provide distinct moieties that can be detected via e.s.c.a. to provide a surface count of induced species. Hydroxyl, epoxy, hydroperoxy, carboxylic acid and carbonyl populations are discussed as a function of corona energy input, time after treatment and water washings.

X-ray photoelectron spectroscopy (XPS) has been used to study the chemical effects of both inert (argon) and reactive (oxygen, nitrogen, and mixed gas) plasma treatments done in situ on a variety of polymer surfaces. Inert gas plasma treatments introduce no new detectable chemical species onto the polymer surface but can induce degradation and rearrangement of the polymer surface. However, plasma treatments with reactive gases create new chemical species which drastically alter the chemical reactivity of the polymer surface. These studies have also shown that the surface population of chemical species formed after plasma treatment is dependent on both the chemical structure of the polymer and the plasma gas. The effects of direct and radiative energy-transfer processes in a plasma have also been studied. Polymers containing certain functional groups were found to be more susceptible to damage via radiative energy transfer. Ageing studies of plasma-modified polymer surfaces exposed to the atmosphere have shown that the ageing process consists of two distinct phases. The initial phase, which occurs rapidly, involves adsorption of atmospheric contaminants and, in some cases, specific chemical reactions. The second phase, which occurs slowly, is due to surface reorganization.

This work reports adhesion behaviour of polyethylene on paper, and deals with the surface energy of the materials involved in the manufacture of these composites, and its influence on the adhesion strength, at constant roughness, for the paper substrates. The surface energy of different papers treated with various sizing agents was determined by measuring contact angles according to the Owens-Wendt method. The peeling energy was shown to follow a linear relationship versus the reversible energy of adhesion. This result is explained by the fact that rupture takes place at the interface and that the size of the defect at the interface depends on the spreading coefficient. Corona treatment, applied to strongly sized papers before making the composites, restored the adhesion strength to its original range of values, again demonstrating the thermodynamic character of adhesion in thermoplastic-paper composites.

Once capillary pressure and permeability are determined for saturations ranging from near zero to 100%, liquid transport related to both wicking and wetting behavior can be described by Darcy's equation. The purpose of the work reported here is to assess and develop experimental techniques that allow capillary pressure and per meability to be measured over a wide range of saturations. Cotton and polypropylene fabrics are the test materials. Capillary pressure head is measured as a function of saturation for cotton and polypropylene fabric samples using the column test, and permeability is measured as a function of saturation using the siphon test. The siphon test works for cotton but not for polypropylene. A new method using a transient measurement technique is developed to determine the permeability of both samples as a function of saturation; it works well for both samples.

A roll-coating experimental system is used to study the effect of pre-wetting on dynamic contact angles, the interfacial displacement depth, and the associated phenomenon of air entrainment. The system consists of a roll, which is horizontally rotating in a liquid pool. The dynamic contact angle is recorded by a macrophotography system. The test liquids are glycerol solutions with viscosities in the range 104 < μ < 748 mPa · s. The value of (μV/ρg)^0.5 is taken as the characteristic length to be used in the dimensionless relationships which correlate experimental measurements. The effect of base layer entry angle into the liquid pool on the dynamic contact angles and other flow parameters is studied. Comparison is made with measurements in dry tape-coating and other pre-wet roll–coating systems.

Knowing that the oriented positive ion bombardment plays an important role in the plasma treatments of polymers, some investigations using a positive ion beam-plasma system were carried out. Preliminary results concerning the surface modifications of poly (ethylene terephthalate) films induced by the action of oxygen ion beam are presented. Ion energies (50-500 eV) and doses (3.0 x1015 1.5 x1016 ions/cm²) are those used in a reactive ion etching device. Techniques such as: determination of the surface free energy components by the contact angle method, thermal methods (DTA, DSC, etc.), IR spectroscopy, SEM, XPS, were used to characterize the surface modifications. The relation between chemical and physical modifications is discussed.

Surface modification of Kapton polyimide film (325 nm thick) by means of chromic acid and perchloric acid at different times and temperatures has been carried out. The contact angle of water decreased from 82 to 55° and the surface energy increased accordingly from 26 to 45 mJ/m² with times of etching by chromic acid up to 45 min at 33°C. Etching at higher temperatures increased the surface energy. Chromic acid was more effective than perchloric acid. IR and XPS studies indicated multiple bonding and generation of poler groups on the surface. The peak at 1778 cm^-1 due to the imide group decreased on acid etching. The O/C ratio increased and the N/C ratio decreased. The peel strength of the joint polyimide film/copper film/epoxy adhesive/aluminium sheet increased about two-fold on modification of the polyimide (PI) film at 33°C for 45 min, although the changes were marginal for the PI film/silicone rubber/PI film joint. The peel strength is a function of the time and temperature of etching.

This paper contains a brief overview on the recent developments of corona charging of polymers, with emphasis on the current corona triode. This latter method, which has been successfully applied to several types of polymer, is a legacy from Prof. Bernhard Gross' work in São Carlos, Brazil. Following a short introduction to corona charging, the experimental setups are described, especially with regard to the advantages in the constant current method. A few examples are given of the use of the constant current corona triode in the investigation of electrical properties of nonpolar and ferroeleectric polymers. The application of corona charging to pole nonlinear optic (NLO) polymers is discussed, including the perspectives for the constant current charging method for the NLO field.

The properties of a polymer surface can be decisive for the function of the polymer. Both in the assessment of existing polymer systems and the development of new ones the possiblity of characterizing the chemical composition and structure of the polymer surface becomes important. Various instruments and chemical methods used to characterize polymer surfaces and interfaces are reviewed. The pros and cons of electron spectroscopy for chemical analysis and derivatization schemes to enhance the detectability of functional groups, Fourier transform infrared spectroscopic methods (ATR, RIFT, PAS, micro), Raman spectroscopy, static secondary ion mass spectrometry, high resolution solid state nuclear magnetic resonance, microscopy and contact angle measurements are presented. The importance of the fact that the polymer surface can undergo comparatively rapid reorientations leading to a changed surface chemistry is discussed and exemplified.

Blown film processors, large and small, have limited resources in both capital and manpower to devote to optimizing their productivity. Yet avenues of improvement are open for even the most over-extended organization. And some of the most effective modifications cost little more than a small change in equipment orientation or procedures. A key aspect of optimizing a blown film layout is line footprint and determining how to minimize footprint and maximize output with each integral piece of equipment on the line. Multiple surface treatment systems are integral to every blown film line and can control product quality and line efficiencies. The objective of this work is to present best practices of blown film manufacturers ranging from multinationals to small privately owned operations relative to the most effective surface treatment system designs, their roll coverings, optimum power density settings, alternative treatment technologies, troubleshooting protocols, and model line layouts that optimize production output.

A basic understanding of rheology and surface chemistry, two primary sciences of liquid flow and solid-liquid interaction is necessary for understanding coating and printing processes and materials. A generally qualitative treatment of these subjects will suffice to provide the insight needed to use and apply coatings and inks and to help solve the problems associated with their use. Rheology, in the broadest sense, is the study of the physical behavior of all materials when placed under stress. Four general categories are recognized: elasticity, plasticity, rigidity, and viscosity. Our concern here is with liquids and pastes. The scope of rheology of fluids encompasses the changes in the shape of a liquid as physical force is applied and removed. Viscosity is a key rheological property of coatings and inks. Viscosity is simply the resistance of the ink to flow-the ratio of shear stress to shear rate. Throughout coating and printing processes, mechanical forces of various types and quantities are exerted. The amount of shear force directly affects the viscosity value for non-Newtonian fluids. Most coatings undergo some degree of" shear thinning" phenomenon when worked by mixing or running on a coater. Heavy inks are especially prone to shear thinning. As shear rate is increased, the viscosity drops, in some cases, dramatically. This seems simple enough except for two other effects. One is called the yield point. This is the shear rate required to cause flow. Ketchup often refuses to flow until a little extra shear force is applied. Then it often flows too freely. Once the yield point has been exceeded the solidlike behavior vanishes. The loose network structure is broken up. Inks also display this yield point property, but to a lesser degree. Yield point is one of the most important ink properties.