In this work we studied the effect of surface treatment of PET films, which are widely used in food packaging, on the adhesion value of ink layers based on polyvinyl chloride. To give high barrier properties to packaging laminates, the films used in their structure are coated with a nanolayer of aluminum oxide (AlOx). However, these films have a disadvantage associated with the low adhesion of adhesive and ink layers to the AlOx nanolayer. To eliminate this disadvantage, aluminium oxide nanolayer is additionally coated with various polymer coatings. In this work we studied the effect of a polyacrylic coating applied on top of an AlOx layer on improving the adhesion of ink layers. For PET films used in food packaging, optical and surface properties are also important. In this regard, additionally we measured surface free energy, coefficient of friction, and optical properties of the studied PET films. We also highlight the relationship of contact angles of wetting and the work of adhesion for the printing ink with the measured adhesion of ink layers.

In order to achieve a complete understanding and control of plasma processes an appropriate knowledge of the structure of the particular glow discharge utilized is necessary. This is extremely important because the electrical potential distribution inside a plasma reactor is not uniform and therefore, as a function of the reactor geometry and sample position, charged particles are accelerated from the plasma bulk to the substrate to be treated by different potential drops, ie they impinge on different surfaces with different energy.

The lack of data concerning all the species and the microscopic phenomena involved in low pressure plasmas has always been the major obstacle for the complete understanding of the process mechanisms. As a matter of fact, even today, there is no gas-discharge system for which we can have, by whatever diagnostic tools, a complete picture of the concentration profiles of the species, either charged or neutral, involved in the various gas phase, gasfield, and gas-surface interactions (figure 1). This is more pronounced as we go from simpler noble or molecular gas plasmas to the more and more complex" chemical" plasmas used for the deposition of thin films. The main difference between classical chemical reactors and these plasma reactors comes from the presence of the electromagnetic field in interaction with various charged particles and surfaces. This makes the different plasma processes not easily predictable, controllable and comparable with each other. The rf power used in all these processes implies special reactor design and operation regimes which are different from the idealized plug-flow (PFR) or continuous stirred tank (CSTR) chemical reactors. Therefore, what one measures outside the reactor has no straightforward relation with what is happening inside, and there is no universal way of translating this information since, the" reacting gas volume" is not known, isotropic or homogeneous, while all the microscopic plasma quantities are also functions of space, in the specific reactor. On the other hand, a variation of one of the process parameters, like power or pressure, is not only associated with a change in the value of other macroscopic and microscopic quantities, but also with the way they interact with each other, with the electric field, and the surrounding surfaces. Two basic requirements arise from the discussion above: the need for more efficient, yet simple, non-intrusive diagnostics, and the need for more accurate process control. In fact, both requirements end up to the need for more accurate measurements. This is essential if the characterization of the discharge in a universal way is to be pursued, and it is also the main prerequisite for understanding the basic mechanisms governing the process, for building realistic mathematical models and in general for the development of the discharge theory.

In recent years, fluorocarbon plasmas have been extensively used for the treatment of polymer surfaces in an increasing number of applications. A decrease of the surface wettability is observed after exposure of the polymer to the discharge, to a degree depending on the treatment time and discharge parameters. Fluorination of the polymer surface, following exposure of the surface to the discharge, is believed to be the result of functionalization and/or polymerization, depending on the plasma composition. However, due to the complexity of the chemical reactions both in the gas phase and at surfaces, the underlying mechanisms are not yet well understood. The characterization of the reactive species formed in the discharge and the possible correlation of their behaviour to the plasma-induced modification of the surface properties is essential for understanding the role of the species and for the identification of the mechanisms of surface modification. Fluorocarbon radicals can be detected in situ by a number of diagnostic techniques, that include optical emission spectroscopy [1], laser-induced fluorescence (LIF)[2-4], UV absorption [5], infrared diode laser absorption spectroscopy (IRLAS)[6-8], and threshold ionization mass spectrometry [9-11].

According to the concept described by Langmuir in 1938 [1], the surface properties of a solid are determined by the surface-configuration (spatial arrangement of atoms at the interface) rather than the configuration of molecules which occupy the top surface region. In other words, whether a polymer surface is hydrophilic or hyrophobic cannot be predicted by the presence or absence of hydrophilic moieties in the molecules, but is determined by whether or not the hydrophilic moieties are located at the interface. In recent years, it has been recognized that the surface of a solid, particularly polymeric solid, is very different from what can be anticipated from the bulk characteristics of the same material. This discrepancy has been a focal point of the general phenomena recognized by the terms surface dynamics, surface reconstruction, etc., which deal with the change of chemical and morphological properties of polymer surface due to the change of the surrounding medium [2-14]. The surface dynamic change depends on the reference state from which the change takes place, and if one cannot define the reference state, the surface dynamics cannot be dealt in a generic sense. This problem was indeed found with moderately hydrophilic copolymer of ethylene/vinyl alcohol. The reference state depends on the history of a sample, and the change cannot be reproduced without precise knowledge of the history of a sample [15]. According to the view that a polymeric surface is an ever-changing entity depending on the surrounding medium [16], the restructured surface is not necessarily the final one to stay, ie, restructuring of once restructured surface or multiple repeated restructuring occur with highly perturbable polymeric surfaces. Therefore, the term" surface reconstruction" is intensionally avoided in the discussion of surface dynamics in this article. The change of surface is expressed by the change of surface-configuration.

Many useful processes for treating solid surfaces can be carried out by plasma methods. However, most previous work was done at low pressure, usually less than a few torr. For such low pressure processes, the vacuum apparatus requires great cost and is not suitable for the treatments of large scale substrates such as long film rolls. We previously reported that surface fluorination and thin film deposition could be carried out with the atmospheric pressure glow plasma (APG) process [1]. This approach can reduce apparatus costs and can also be applied to high vapor pressure substances such as gum, textiles and biomaterials. In this article, we will discuss the mechanism of stabilization of glow plasma at atmospheric pressure and report examples of applications of this technology.

A low pressure plasma comprises a complex mixture of electrons, charged and neutral molecules and fragments in the ground state and excited states, and a broad spectrum of radiation ranging from the infrared to the far ultraviolet. The specific role of each of these components in a plasma treatment of polymers is still not understood completely. The experimental data reported in the literature seem to be contradictory.

Low-pressure plasma processing of materials can be divided into three categories, namely (A) etching (removal of material),(B) deposition (addition of new material to a surface), and (C) modification (morphological, structural, and physicochemical change of the surface or near-surface region). In industries which make extensive use of low-pressure plasmas (for example, in the manufacture of integrated circuits-IC, the treatment of polymers for improved adhesion, etc), the above-named changes are deliberate and highly beneficial. However, there exist many instances where treatment can turn into a liability, or where plasma-chemical changes occur involuntarily and are a priori detrimental. The main objective of this chapter is to sensitize the reader to the existence of circumstances where plasma effects can be deleterious, for example:(1) Corona discharges, also known as silent discharges or dielectric barrier discharges, are a form of plasma which occurs when insulating materials are exposed to an alternating source of high voltage (~ 10 kV). Corona is comprised of multitudes of ultra-rapid (~ 100 ns), narrow (~ 100 μm) filamentary micro-discharges, which impinge upon the dielectric surface. Since the 1950s corona is being used commercially for treating polymeric webs up to 8 m in width, so as to render them printable (process category (C) above). However, corona treatment (like its low-pressure counterpart) can be detrimental if" overtreatment" occurs: If the reagent gas, like ambient air, contains oxygen, low-molecular-weight oxidized materials (LMWOM) form on the surface, and these can give rise to a weak boundary layer. This laboratory has compared corona and glow discharge treatment of LDPE and PET, using peel strength and XPS measurements, and has found similar" optimum" treatment criteria for both types of processes: High treatment (oxidation) levels could be correlated with elevated concentrations of acidic (O= C-O) reaction products and low peel strength.(2)

Surfaces and interfaces exhibit a rich variety of phase transitions. While some of these phase transitions also occur in the bulk, others involve coupling between surface and bulk degrees of freedom; consequently the surface phase diagram may be rather complex even for simple Ising like systems. In these lectures I will introduce the generic 4-dimensional surface phase diagram (bulk and surface couplings, bulk and surface fields) of Ising like systems and discuss bulk vs. surface criticality. I will start with a review of surface thermodynamics and scaling of interfaces with emphasis on wetting phenomena. Then Landau mean-field theory is used to calculate the global surface phase diagram. The effects of thermal fluctuations are discussed using the capillary wave Hamiltonian: The correlation functions are calculated using Ornstein-Zernike theory for systems with short and long-range forces. Finally, I will comment on the status of the renormalization group results for 3-dimensional short-range critical wetting that are at odds with the results of simulations of the Ising model and of a recent experiment.

These lecture notes discuss some theoretical approaches for the prediction of the structure, thermodynamics, and dynamics of polymers at interfaces, with emphasis on self-consistent field (SCF) methods. We begin with simple models for the conformational statistics of unperturbed chains and derive the Edwards diffusion equation for a Gaussian thread in a field. We then describe a simple lattice-based approach for a polymer melt at a flat interface and results from its application. Next, we discuss mixing energetics in the lattice model and outline an extension of the lattice-based SCF theory to treat copolymers at interfaces. Correspondences are pointed out between lattice-based and continuous SCF approaches, the latter making use of the Edwards diffusion equation. As an example of continuous formulations we present Helfand and Tagami’s elegant analytical solution for a flat interface between two immiscible polymers in the limit of very large molecular weights. Following Fredrickson et al., we outline a general fieldtheoretic approach for the mesoscopic modelling of inhomogeneous polymer systems. Using a symmetric diblock copolymer as an example, we show how a saddle point approximation reduces this formalism to a SCF theory and discuss the phase diagram obtained through continuous SCF by Matsen and Schick. As an example of scaling considerations, we derive expressions for the chain length dependence of the long period of the lamellar phase of the diblock copolymer. The latter part of the notes focusses on applications and comparisons with experiment. We discuss the structure of polymer/polymer and solid/polymer interfaces in the presence of diblock copolymers. We then briefly review a hierarchical theoretical/simulation approach for exploring adhesion at a solid/polymer interface strengthened by chains terminally grafted to the solid.

In this work, the effect of corona discharge treatment on surface properties of polyimide film was investigated in terms of FT-IR(Fourier Transform-IR), XPS(X-ray Photoelectron Spectroscopy) and contact angles. And the adhesion characteristics of the film were studied in peel strengths of polyimide coatings. As a result, polyimide surfaces treated by corona discharge led to an increase of oxygen-containing functional groups or polar component of the surface free energy, resulting in improving the adhesion characteristics of the polyimide/copper foil. However, the surface energy of the film was decreased as the aging time increased. These results could be discussed in the formation of surface functional groups or deterioration of reactive sites of polyimde film in the presence of corona treatment with aging time.