Polyimide films are currently of great interest for the development of flexible electronics and sensors. In order to ensure a proper integration with other materials and PI itself, some sort of surface modification is required. In this work, microwave oxygen plasma, reactive ion etching oxygen plasma, combination of KOH and HCl solutions, and polyethylenimine solution were used as surface treatments of PI films. Treatments were compared to find the best method to promote the adhesion between two polyimide films. The first selection of the treatment conditions for each method was based on changes in the contact angle with deionized water. Afterward, further qualitative (scratch test) and a quantitative adhesion assessment (peel test) were performed. Both scratch test and peel strength indicated that oxygen plasma treatment using reactive ion etching equipment is the most promising approach for promoting the adhesion between polyimide films.

New helical coupling plasma system for continuous surface treatment and modification (surface processing) of fiber bundles has been developed and tested for glass fibers. The system enables surface processing of single filaments and flat substrates as well. Surface processed glass fibers and their bundles were examined as reinforcements for glass fiber/polyester composite systems. Processing of fibers comprised a surface treatment using argon gas and a surface modification using hexamethyldisiloxane and vinyltriethoxysilane monomers. Interfacial and interlaminar shear strengths of plasma processed glass fiber/polyester systems were compared with those of untreated and commercially sized fibers.

Contact angle measurement has wide application in studying the wettability of a surface. This paper presents a contact angle measurement system developed using simple apparatus. The system consists of a bespoke measurement software, USB microscope, motorized linear position slider and a sample holder with back lighting system. The advantages of this system include user friendly, compact size, allow manual and automatic measurements and cost effective. This system is established with the contact angle and surface tension measurement experiment which is based on Fox-Zisman theory. Different probe liquids were suggested and the critical surface tension of polydimethylsiloxane (PDMS) and polyimide were determined using both the software and the hardware system developed.

The mechanics of adhesion have been investigated both theoretically and experimentally, using model adhesive joints consisting of a crosslinked amorphous rubber bonded to a variety of rigid polymeric substrates.

An adhesive failure energy, θ, is defined which is characteristic of the bond but independent of test-piece geometry. Both theory and experiment show that θ has the form, θ=θ₀f(R) where θ₀ is the “intrinsic adhesive failure energy” which depends only on the physical and chemical nature of the adhesive-substrate interface, and f is a function of R, the “reduced” rate of failure propagation obtained from rate and temperature data using the WLF equation.

θ₀ is the work of bond fracture across the interface and, for clean interfacial failure, is equal to the thermodynamic work of adhesion w_A. Where failure is not purely interfacial, θ₀ can be expressed as θ₀=iI+r𝒯₀+sF where i, r, and s are respectively the area fractions of interfacial, cohesive-in-rubber and cohesive-in-substrate failure, and I, θ₀, and F are the intrinsic failure energies for the interface, rubber, and substrate, respectively.

It is believed that this work is the first to demonstrate explicitly and quantitatively the separate contributions of interfacial properties and bulk rheological behavior to the strength of adhesive joints.

The solid-vapour surface tension has been determined by contact angle measurements with polar and non-polar liquids on flat solid surfaces using Axisymmetric Drop Shape Analysis (ADSA) and by capillary penetration experiments on rough and porous solids. For smooth and inert, well prepared solid surfaces (PTFE, FC 721 on mica, FEP, PET) the plot of γ_lvcosΘ versus γ_lv yields smooth curves which are consistent with the equation of state approach to calculate solid-vapour and solid-liquid interfacial tensions. Other experimental patterns of contact angle data are caused by surface roughness and non-inert solids which may result in contact angles incompatible to Young’s equation. An alternative way to obtain the solidvapour surface tension of rough and porous solids are capillary penetration experiments. The determination of the penetration velocity of liquids into rough and porous solids yields Kγ_lv coΘ versus γ_lv plots, which provide γ_sv values for these systems; K is an unknown parameter of the constant geometry of the porous solid. The application of this concept was demonstrated for a hydrophobic PTFE powder and for hydrophilic Cellulose membranes.

Recent progress in the correlation of contact angles with solid surface tensions are summarized. The measurements of meaningful contact angles in terms of surface energetics are also discussed. It is shown that the apparent controversy with respect to measurement and interpretation of contact angles are due to the fact that some (or all) of the assumptions made in all energetic approaches [7–14] are violated when contact angles are measured and processed. For a large number of polar and non-polar liquids on different solid surfaces, the values of γ _1v cos θ are shown to depend only on γ _1v and γ_sv when the appropriate experimental techniques and procedures are used. An equation which follows these experimental patterns and which allows the determination of solid surface tensions from contact angles is discussed.

This article focuses on recent advances in the understanding of industrial gas burners. Ribbon burners have been chosen as the focus of the review because of the advantages presented by the burner arrangement and burner performance. The ribbon burner configuration, because of its ability to provide large flame surface and flame stabilization, has a large range of stability as flow rate, equivalence ratio and reactant gas composition are varied. Discussed in detail is the application of ribbon burners in the surface modification, or flame treatment, of polymer films to increase the wettability of a polymer surface. Optimum treatment requires a spatially homogeneous post-flame reaction zone even with burners up to 3 m in length. For methane/air flames, the optimum equivalence ratio is near 0.93 where the active oxidizing-species concentration near the surface is a maximum. Chemical kinetic models of the impinging flame and surface oxidation chemistry of a polymer film are also discussed. The model predictions are in good qualitative agreement with the available understanding of the flame variables affecting surface treatment and the expected oxidized species on the polymer surface.

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.

We have been able to generate the wide and stable plasma in open air (discharge distance, 35 cm; discharge-electrode length, 16 m at maximum) using a pulse with a high voltage and narrow wave form. This was applied to treat the surface of rather non-polar plastics intended for the improvement of adhesion of over-coated layers such as coatings, adhesives and printing inks. The treating system (APPS) consists of the apparatus for generating the plasma and the treating process. Polypropylene (PP) and tetrafluoroethylene perfluorovinyl ether copolymer (PFA) have been examined as typical examples of the plastics. The adhesion strength of urethane paint on PP molding and of a PFA film on steel was significantly improved by the APPS treatment. The characteristics of the surface layer were evaluated by means of scanning electron microscopy, electron spectroscopy for chemical analysis, atomic force microscopy, and contact angle measurement, and it was found that hydrophilic functional groups were introduced into the surface layer of the plastics. The level of the improvement changed with time after treatment; this is discussed from the viewpoint of functional group movement from the surface to the interior. Application of paints on PP bumpers by the electrostatic spray method was also accomplished. The use of a small amount of nitrogen-containing compound following APPS treatment decreased the electrical resistance of the PP surface from 10¹⁶ to 10¹¹ Ω, and highly effective electrostatic coatings of PP bumpers could be realized.

The surface energy of coating layers influences their final properties such as their ability to repel or absorb fluids. Recent work has shown that the substrate, due to absorption, can alter the surface chemistry of the top coating layer. However, the influence of substrate properties on coating surface energies is not reported in the literature.Three coatings, based on a pigment and a latex binder, are applied on three different substrates that differ in terms of absorption properties. The three coatings were also modified with a soluble polymer. Contact angle measurements of three different probe fluids were measured. These contact angles were used to estimate the polar, dispersive, and total surface energy of the coating layers. Surface energies were also determined for the latex and pigments.The contact angles and surface energies of the latex films and pigments agree with the expected results. Most of the results for the coating layers agree with the reported surface chemistry of these coatings. Large pigment systems on absorbent substrates have a high contact angle and low surface energy. These results agree with the expected results based on the surface chemistry reported in past work. The results for the fine pigment system had low contact angles and high surface energies and did not agree with the expected results. The contact angles may be influenced by the surface roughness of the coatings or the expected surface energy of a heterogeneous surface may not be a simple function of the surface composition.

The performance of water-based acrylic flexographic inks laboratory printed on three different polymer-coated boards, namely coated with LDPE, OPP and PP, have been analysed and interpreted. The print quality and resistance properties obtained were related to varying ink formulation, in particular choice of emulsion polymer and presence of silicone additive in the vehicle, as well as varying levels of corona pretreatment. Print mottle and adhesion were worst on PP, while wet (water) rub and scratch resistance were worst on OPP and PE, respectively. However, these properties could be greatly influenced by the ink formulation, more so than corona level. In general addition of silicone improved scratch resistance, due to reduction in polar energy component of the print surface, but at the expense of worsened wet rub resistance. The emulsion polymer giving best resistance performance was generally found to give poorest optical properties, presumably due to more limited resolubility on press.

Paperboard was coated on a pilot scale using aqueous dispersions of styrene–butadiene (SB) copolymers in order to improve its surface characteristics (including printability) and barrier properties with regard to the transmission of water vapour. Coating the paperboard with the dispersion in two steps gave a smoother surface with a remarkable increase in gloss. The printing properties of the smoother double-coated surface were slightly better than those of the single-coated surface. Paraffin wax added to the latex dispersion reduced the water vapour transmission rate (WVTR) but had a negative effect on the printability of the board.

The effect of two commonly used surface treatment techniques (corona and plasma at atmospheric pressure) on the printing and barrier properties of dispersion-coated (containing wax) paperboard was evaluated. A fairly intense corona treatment led to an undesirable increase in the WVTR-value. A less intense corona treatment preserved the WVTR-value to a great extent, but the printability remained at an unsatisfactory level. With plasma treatment, the water vapour barrier was not impaired, and the printability of the plasma-treated dispersion-coated (wax-containing) substrate was good. It is suggested that a better result using corona treatment may be obtained by optimising the power and controlling the time between the treatment and the printing, although this was not investigated here.

Many coatings materials are based on polymeric materials and sometimes difficulties arise when trying to marry them to polymer substrates of low surface energy and relatively inert molecular structure. Through the application of tailored coating formulation, substrate surface pretreatment and suitable coating process these problems may be eliminated to produce coated polymers with high bond strength properties.

Surface layer of com. polylactide (PLA) was modified with corona discharges and studied for contact angle (H2O, CH2J2) and the geometric structure (at. force microscopy). The surface free energy was caled, by using Owens-Wendt equation. The treatment resulted in a decrease in the contact angle and an Increase in the surface free energy of the PLA film.

The paper investigates the effect of corona discharge (CD) treatment on the properties of surface layer (SL) of polylactide (PLA) film. The modification of PLAwas carried out in the air and helium atmosphere and the results were compared on the basis of the assessment ofwettability, surface free energy (SFE) calculated using Owens-Wendt method aswell as the degree of oxidation (O/C) of the modified SL, determined by photoelectron spectroscopy.

X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to characterize the surface modification and possible production of low molecular weight reaction products on biaxially oriented polypropylene (BOPP) and on low density polyethylene (LDPE) films treated by atmospheric pressure glow discharge (APGD) in pure nitrogen and by air corona. We have observed that surface degradation is more pronounced for air corona treatments in the case of both polymers.

Cohesion parameters (solubility parameters) provide one of the simplest methods of correlating and predicting the cohesive and adhesive properties of polymers and solvents from a knowledge of the properties of the individual components alone. It is therefore not surprising that there are severe limitations on their precision. Whether or not any correlation or prediction is ‘satisfactory’ depends on the precision that is expected or needed. When one is looking for relatively minor differences in behaviour, such as solubility differences between isomeric liquids or between polymers with different degrees of cross-linking, cohesion parameters may not be appropriate. The most important situation where caution is required in using Hildebrand parameters or Hansen parameters is where the extent of donor-acceptor (Lewis acid-Lewis base) interactions(particularly hydrogen bonding) within a component is very different from that between components.

Etching and modification of polymers by plasmas is discussed in terms of the roles played by atomic and molecular oxygen, atomic fluorine, CF_x radicals, ions, high energy metastable species, and photons. Addition of fluorine-containing gases to oxygen can increase both 0 atom densities in the plasma and polymer etching rates. The etching rate be- havior generally exhibits a maximum at a specific concentration of this additive. Process parameters which alter the concentrations of 0 and F atoms in the plasma or affect the rate of delivery of these species to the polymer surface shift the position of this maximum with respect to feed gas composition. However, the gas composition which yields maximum rates exhibits a strong dependence on polymer structure, specifically, its degree of unsaturation. This is explained on the basis of molecular orbital (MO) arguments which predict that the surfaces of unsaturated polymers have a higher affinity than saturated polymer surfaces for atomic fluorine. Favored reaction pathways leading to volatile etching products are pro-posed based on MO calculations of relative bond strengths for various oxygenated and fluorinated organic model compounds. Although fluorine abstraction of hydrogen plays a major role in generating radical sites on saturated polymer surfaces, it is likely that etching of unsaturated moieties proceeds through a saturated radical intermediate resulting from addition reactions of fluorine atoms. Excessive amounts of fluorine in the plasma result in reduced etching rates and incorporation of fluorine and/or CF_x radicals into the polymer. Polymer film surfaces are also modified by high energy metastables and ultraviolet radiation generated from noble gas plasmas, The effect of vacuum ultraviolet radiation from helium microwave plasmas on films of polytetrafluoroethylene and polyethylene is addressed.

The main properties of corona discharges are reviewed, with emphasis on the features which make them unique for use as non-equilibrium chemical reactors : Their stability andease of operation over a wide range of gasesand pressures, including atmospheric : their sharply confined ionization regions where hot electrons interact with cold gas, inducing reactions without back reactions ; and their extended low field drift regions which act as gaseous electrolytes, inducing electrochemical reactions on surfaces. Present and future applications are discussed : Synthesis of ozone and ammonia, promotion of flames and combustion, surface treatment, and electrical insulation improvement.

A recent study has illustrated a sizeable increase in the printing characteristics of nonwovens following atmospheric plasma treatments. The improvement of properties such as wettability, printability and adhesion opens up new application prospects for treated fabrics.

The surface functionalization of polyimide (Matrimid^® 5218) films was carried out by cold plasma treatment with CF₄, N₂ and O₂ gases using a radio frequency discharge and the optimum plasma conditions were evaluated by water contact angle measurements. The surface hydrophobicity of polyimide films was obtained after CF₄ plasma treatment, while O₂ and N₂ plasma treatments contributed to the hydrophilic surface functionalization. X-ray photoelectron spectroscopy (XPS) results revealed the presence of CF_x, amino or oxygen-containing groups attached to the polyimide film surface depending on the treatment gas. A strong influence of the used plasma gas on the film roughness was determined by atomic force microscopy (AFM) measurements. The influence of the surface modification on CO₂, N₂ and O₂ gas permeation through the plasma treated films was evaluated. The permeation behaviour was characterized in terms of transport parameters, namely, coefficients of permeability, diffusion and solubility. The permeability coefficient of all plasma treated polyimide films for the studied gases (CO₂, N₂ and O₂) was found to decrease following the order of increasing the kinetic molecular diameter of the penetrant gas. Besides, the selectivity coefficient was found to be significantly increased after the plasma treatments – α_CO2/N2 was increased up to 36% and 98% for O₂ and N₂ plasma treated Matrimid^® 5218 films, respectively. The relationship between the gas permeation behaviour and the surface modification of polymer film by cold plasma was discussed.

In moist environments biaxially-oriented corona-treated polyethylene terephthalate (BOPET) film undergoes a decay in surface energy with time. This decay is a significant and well-known problem and it considerably restricts the industrial application of BOPET film. In the present study the decay effect and the dynamics of corona-treated BOPET film in an aqueous environment have been studied using water contact angle and variable angle X-ray photoelectron spectroscopy (XPS) measurements. In addition the surface decay mechanism of the corona-treated BOPET film in aqueous environments was analyzed and a molecular moving model for the decay mechanism is proposed.

Plasma chemistry of polymers may be categorized into two major types of reactions as (1) surface reaction of polymers and (2) polymerization of monomers by plasma. So far as these two types of reactions are concerned, plasma is very similar to other ionizing radiation, such as ..gamma.. radiation, x radiation, UV radiation, and high-energy electron beams, which can (1) initiate polymerization of certain monomers, and create free radicals on polymer exposed, which lead to (2) crosslinking of the polymer and/or (3) degradation of the polymer, or can be further utilized as the initiation sites of (4) graft copolymerization. The characteristic features of plasma are (1) the radiation effect is limited to the surface, and the depth of the layer affected by the plasma is much smaller than that by other more penetrating radiation, and (2) the intensity at the surface is generally stronger than that by the more penetrating radiations. Therefore, plasma treatment provides an ideal means of modifying surface properties of polymers. Examples are presented and discussed.

Drop-on-demand inkjet printing, familiar to most of us from small home and office printers, is taking an increasing role in printing for the broader commercial and industrial market. Inkjet printing has made serious inroads into the market for printing banners and signs of all sorts. Wide-format and super wide-format printing is now the norm and has, to an increasing degree, superseded analog printing as the method of choice for printing large format and point-of-purchase signage. Overall, inkjet printing has now taken over 30 percent of the general sign and banner market. One area of printing that holds promise for future growth is that of packaging and labels. Many forms of commercial printing, although a huge market today, are threatened on multiple fronts from various forms of electronic media. Printing and decoration for packaging, on the other hand, is expected to increase in volume in the foreseeable future. In spite of this great promise, penetration of digital printing, in general, and inkjet printing, in particular, into packaging and label printing is still in the low single digits. This article will focus on the label market as an example of printing for packaging. Printing for packaging is a much broader and diverse subject than just labels, but many of the conclusions that follow can be extrapolated to the broader packaging market. Toner-based methods, both wet and dry, have been at the vanguard of penetrating the label market. Today, inkjet is slowly gaining market share. Inkjet has great potential because there is more flexibility in the type and characteristics of fluids that can be applied from an inkjet head. While there are many possible explanations for the relatively low penetration of digital printing into this market, this article will concentrate on the technical challenges involved in reliably printing labels of acceptable quality with inkjet printing. Only now is the inkjet printing industry overcoming these challenges.