In the study reported in this paper, a series of reproducible conditions were employed to uniformly functionalize nylon 6 surfaces using a commercially available, low-frequency (40 kHz), low-pressure plasma system, utilizing oxygen plasma as a reactive gas. Initially, the plasma-treated samples were investigated using static contact angle measurements, showing a progressive increase in wettability with increasing plasma activation time between 10 and 40 s. Such an increase in wettability (and therefore increase in adhesive capabilities of the surfaces) was attributed to the creation of surface C-OH, C=O, and COOH groups. These surface-chemical modifications were characterized using x-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS). Surface radical densities were also shown to increase following plasma activation, having been quantified using a radical scavenging method based on the molecule 2,2-diphenyl-1-picrylhydrazyl (DPPH). The samples were imaged and analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), to confirm that there had been no detectable alteration to the surface roughness or morphology. Additionally, the “hydrophobic recovery” or “ageing” of the activated polymer samples, post-plasma treatment, was also investigated in terms of wettability and surface-chemistry, with the wettability of the sample surfaces decreasing over time due to a reduction in surface-oxygen concentration.

In modern technology, there is a constant need to solve very complex problems and to fine-tune existing solutions. This is definitely the case in modern medicine with emerging fields such as regenerative medicine and tissue engineering. The problems, which are studied in these fields, set very high demands on the applied materials. In most cases, it is impossible to find a single material that meets all demands such as biocompatibility, mechanical strength, biodegradability (if required), and promotion of cell-adhesion, proliferation, and differentiation. A common strategy to circumvent this problem is the application of composite materials, which combine the properties of the different constituents. Another possible strategy is to selectively modify the surface of a material using different modification techniques. In the past decade, the use of nonthermal plasmas for selective surface modification has been a rapidly growing research field. This will be the highlight of this review. In a first part of this paper, a general introduction in the field of surface engineering will be given. Thereafter, we will focus on plasma-based strategies for surface modification. The purpose of the present review is twofold. First, we wish to provide a tutorial-type review that allows a fast introduction for researchers into the field. Second, we aim to give a comprehensive overview of recent work on surface modification of polymeric biomaterials, with a focus on plasma-based strategies. Some recent trends will be exemplified. On the basis of this literature study, we will conclude with some future trends for research.

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 manufacture of polyolefin films by an extrusion process will today almost certainly include as part of the processing line some form of adhesion promoter. For Cast and Blown extrusion this would mean corona as the adhesion promoter. Often overlooked as being an insignificant component on the manufacturing line, the Corona Treater is often purchased in haste and without adequate deliberation. Without this consideration a capital expenditure may arise that may meet current requirements but offers little or no flexibility for the future. When considering a Corona Treater, first and foremost a choice must be made between Bare Roll and Covered Roll. This paper deals with the decision making process leading up to this determination. We will stress that one should not allow any preconceived notions to cloud the issue on the type of treater station required. Both Bare Roll and Covered Roll treater stations serve a particular purpose and play an integral part in the manufacturing process.

Poly(ethylene terephthalate) (PET) Mylar^® samples were treated by corona discharge in order to improve their adhesive properties. The corona treatments were performed in different atmospheres including nitrogen, ammonia and air.

X-ray photoelectron spectroscopy (XPS) was used to investigate the chemical modifications induced at the PET surface by these corona treatments. XPS results show that nitrogen incorporation takes place in the form of non-oxygenated nitrogen functionalities, like amine or cyano groups. These are present at the surface of all the corona-treated samples but in different concentrations depending on the gases used in the corona discharge. Furthermore, XPS analyses performed after heating of the treated samples show a higher thermal stability of the corona-induced surface modifications in the case of nitrogen and ammonia.

Ion scattering spectroscopy (ISS) and static secondary ion mass spectroscopy (SIMS) analyses were also performed because of their higher surface sensitivity compared with XPS: ISS reveals that nitrogen is not present at the topmost surface layer of the treated samples but is incorporated just beneath. The outermost surface layer presents a composition rich in oxygen. Finally, static SIMS spectra show that corona treatment induces more surface degradation when performed in air compared with nitrogen or ammonia.

These results are discussed in relation to adhesive properties of PET.

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.

Paper, although ubiquitous, is a complex material. We can classify paper as a basic network of self bonding cellulosic fibers; the chemical and physical characteristics of its surface are controlled by the raw materials, papermaking and converting processes used to produce it. Paper sometimes contains non-cellulosic fibers such as non-wood and synthetic fibers, chemical additives, fillers, and bonding agents. Other chemical additives used in the papermaking process, e.g., formation, drainage, and retention aids or coating materials may also change the physical and chemical characteristics of the paper's surface. With the greater use of recycled fibers we may expect additional changes in surface chemistry and structure.

The liquid state of matter plays a very important role in everyday life, and the liquid surface has a dominant role in many phenomena. In fact, about 70% of the surface of Earth is covered by water. The most fundamental characteristic of liquid surfaces is that they tend to contract to the smallest surface area to achieve the lowest free energy. Whereas gases have no definite shape or volume, completely filling a vessel of any size containing them, liquids have no definite shape but do have a definite volume, which means that a portion of the liquid takes the shape of that part of a vessel containing it and occupies a definite volume, with the free surface plane except for capillary effects where it is in contact with the vessel. This is evident in rain drops and soap films, in addition to many other systems that will be mentioned later. The cohesion forces present in liquids and solids and the condensation of vapors to liquid state indicate the presence of much larger intermolecular forces than the gravity forces. Furthermore, the dynamics of molecules at interfaces are important in a variety of areas, such as biochemistry, electrochemistry, and chromatography. The degree of sharpness of a liquid surface has been the subject of much discussion in the literature.

The surface of polymer materials has been successfully modified by ion implantation. The plasma-source ion implantation (PSII) technique was applied as a surface modification method for poly (ethylene terephthalate)(PET) films. A mass-separated ion accelerator was used for low energy implantation in poly (vinyl chloride)(PVC) and polyamide (PA). The surface electrical conductivity of these polymers was measured. Using our computer program TRIM-MV for simulation of the accelerated ion transport through the polymers, the penetration depths of bombarding ions in the studied plastic films were calculated. The experimentally observed changes in physical properties cannot be explained by the calculated ion ranges and implanted particle energy distributions. For the experimental conditions used, the chemical structure modification of the polymer surface, polymer material erosion, and gas creation and its diffusion through the surface layer are more important reasons for the modified material characteristics. The kind of bombarding ions and the composition of polymer material are found to be of prime importance.

In this work we modified the surface of polyethylene in order to coat it with highly-fluorinated UV-curable coatings and assure good adhesion between the two polymers. Different methods were investigated, and a successful treatment was the grafting of a monomer containing a group able to dissociate under UV light. The surface modification was assessed by XPS, ATR–FT-IR and AFM analyses. The modified substrate was easily coated with the photocurable fluorinated formulation, and the highly hydrophobic and oleophobic layer formed after irradiation adhered well to the polyethylene substrate.