Polyacetal-copolymer (POMB), polycarbonate (PC), polybutylene terephthalate (PBT), and nylon 6, 6 (PA6, 6) have been treated in an electron cyclotron resonance (ECR) plasma chamber to improve their adhesion properties towards ink. The chemical composition, the surface free energy, and the macroscopic adhesion have been studied by X-ray photoelectron spectroscopy (XPS), contact angle measurements, cross-cut tests, and the Scotch Tape test. Their dependence on the neutral gas, the treatment time, the pressure, and the ageing in air have been investigated. The XPS results reveal that the plasma treatment allows one to clean the surface and, if reactive gases are used, to incorporate new chemical species. The static and dynamic contact angles decrease with the plasma treatment and continue to decrease after contact with air. Very slow hydrophobic recovery is visible in the advancing contact angle, whereas the receding contact angle remains non-measurable even after more than a week of air exposure. Lower pressures and longer treatment times (120 s) lead to better macroscopic adhesion and reproducibility. For optimal treatment conditions (0.5 Pa, 120s N₂ plasma treatment time), the improvement of the adhesion remains excellent after seven days exposure of the sample in air.

The theory of wetting is reviewed with respect to ink transfer which is based upon measured dynamic surface tension and calculated dynamic spreading coefficient. Laboratory gravure ink transfer results are presented for model water based inks with and without isopropanol as the cosolvent on untreated and corona treated polyethylene film. A mechanism of surface tension driven convection is proposed which is consistent with experimental results. The conclusion, which is based upon the proposed mechanism, is that uniform coverage of a water based ink on a nonpermeable substrate is facilitated by the presence of a high vapor pressure low surface tension cosolvent such as isopropanol. When no cosolvent is present, de-wetting and degree of ink mottling appears to be controlled by dynamics longer than one second.

A hexamethyldisiloxane (HMDSO)-RF plasma was used to treat polypropylene (PP) fabrics to achieve an inorganic type surface. The properties of the plasma modified PP were investigated through demand wettability and contact angle techniques. ESCA and ATR-IR spectroscopy indicated the presence of Si  O  Si and Si  O  C based structures. The influence of treatment time on the level of deposition and surface atomic composition was established. Plasma induced molecular fragmentation of HMDSO was determined through GC-MS and high resolution MS analyses of the molecular structures produced from recombination of active species, in the cold trap.

The influence of release agents, impurities and light stabilizers on the mechanisms of pretreatment operations, such as flame or plasma treatment, of thermoplastic materials used in the automotive industry has been investigated by X-ray photoelectron spectroscopy (XPS), zeta potential and contact angle measurements. It is shown that the presence of release agents on thermoplastic polyurethane can be detected by contact angle and zeta potential measurements. Sterically hindered amines (HALS) used as light stabilizers in polypropylene-ethylene-propylene-dienemonomer rubber blends (PP-EPDM) enhance the result of flame treatment whereas the effect of oxygen plasma treatment is not changed by the presence of HALS products.

Polymers have been applied successfully in fields such as adhesion, biomaterials, protective coatings, friction and wear, composites, microelectronic devices, and thin-film technology. In general, special surface properties with regard to chemical composition, hydrophilicity, roughness, crystallinity, conductivity, lubricity, and cross-linking density are required for the success of these applications. Polymers very often do not possess the surface properties needed for these applications. However, they have excellent bulk physical and chemical properties, are inexpensive, and are easy to process. For these reasons, surface modification techniques which can transform these inexpensive materials into highly valuable finished products have become an important part of the plastics and many other industries. In recent years, many advances have been made in developing surface treatments to alter the chemical and physical properties of polymer surfaces without affecting bulk properties. Common surface modification techniques include treatments by flame, corona, plasmas, photons, electron beams, ion beams, X-rays, and γ-rays.

Plasma treatment is probably the most versatile surface treatment technique. Different types of gases such as argon, oxygen, nitrogen, fluorine, carbon dioxide, and water can produce the unique surface properties required by various applications. For example, oxygen-plasma treatment can increase the surface energy of polymers, whereas fluorine-plasma treatment can decrease the surface energy and improve the chemical inertness. Cross-linking at a polymer surface can be introduced by an inert-gas plasma. Modification by plasma treatment is usually confined to the top several hundred ångströms and does not affect the bulk properties. The main disadvantage of this technique is that it requires a vacuum system, which increases the cost of operation.

Thin polymer films with unique chemical and physical properties are produced by plasma polymerization. This technology is still in its infancy, and the plasma chemical process is not fully understood. The films are prepared by vapor phase deposition and can be formed on practically any substrate with good adhesion between the film and the substrate. These films, which are usually highly cross-linked and pinhole-free, have very good barrier properties. Such films find great potential in biomaterial applications and in the microelectronics industry.

Very high-power microwave-driven mercury lamps are available, and they are used in UV-hardening of photoresist patterns for image stabilization at high temperatures. Other applications of UV irradiation include surface photo-oxidation, increase of hydrophilicity, and photocuring of paintings.

Pulsed UV-lasers are used in surface modification in many areas. Pulsed UV-laser irradiation can produce submicron periodic linear and dot patterns on polymer surfaces without photomask. These interference patterns can be used to increase surface roughness of inert polymers for improved adhesion. These images can also be transferred to silicon surfaces by reactive ion etching. Pulsed laser beams can be applied to inert polymer surfaces for increased hydrophilicity and wettability. Polymer surfaces treated by pulsed UV-laser irradiation can be positively or negatively charged to enhance chemical reactivity and processability. Pulsed UV-laser exposures with high fluence give rise to photoablation with a clean wall profile. There are many other practical applications of laser photoablation, including via-hole fabrication, and diamond-film deposition. The present review discusses all these current applications, especially in the biomedical and microelectronics areas.

Six solid surfaces were compared with respect to their surface quality, by measuring advancing contact angles along the solid surfaces (in the vertical and horizontal directions) at constant immersion rate. It was found that surfaces of mica, dip coated in FC-721, Teflon (FEP) heat pressed against mica, and siliconized glass yield essentially constant advancing contact angles at different locations of the solid surfaces and, thus, are well suited to dynamic contact angle measurements. Static and low rate dynamic contact angles of a number of pure liquids were therefore measured on these solid surfaces. Low rate dynamic contact angles were found to be identical with the static contact angles and independent of the velocity of the three-phase contact line (up to 0.5 mm/min).

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.

Adhesion between two substrates is a complex phenomenon which at present is still not well understood. The important existing adhesion models (electrical, diffusion, thermodynamic adsorption, chemical, etc.) are reviewed in order to try to explain their mechanisms. Thermodynamic adsorption is now believed to be one of the most importnat mechanisms by which adhesion is achieved. Difusion and wetting are kinetic means in attaining good adsorption of a polymer at the interface. In the case of this model (thermodynamic adsorption), the notion of surface energy is developed and the importance of this property in the understanding of adhesion phenomena is emphasized. The methods of determining the surface characteristics of low and high energy solids are presented. The role played by acid-base interactions in adhesion is also mentioned.

Excitation with low temperature helium or helium/water plasma and subsequent exposure to air of polyacrylonitrile (PAN) ultrafiltration membranes was used to hydrophilize the surface of these materials. We analyzed the effectiveness of this approach as a function of plasma operating variables including gas phase composition, plasma power, treatment time, and system pressure. Following the changes in physical and chemical composition of the PAN surface resulting from these modifications was a major aspect of this work. Techniques such as the captive bubble contact angle method, ellipsometry, ESCA, and FTIR-ATR were all used. In addition, the formation and lifetime of peroxides during these processes were determined. At low powers (≤ 25 W) and short treatment periods (≤ 30 s), the main chemical conversion of PAN surfaces was simultaneous hydrophilization and stabilization via PAN cyclization. Relatively small water permeability changes were observed as a result of such treatment. © 1995 John Wiley & Sons, Inc.
https://onlinelibrary.wiley.com/doi/abs/10.1002/app.1995.070560304