In this work, low-pressure nitrogen plasma has been used to improve wettability in a polyurethane film. Evaluation of wettability changes has been carried out using contact angle measurements. Furthermore, plasma-treated films have been subjected to air aging to evaluate the extent of hydrophobic recovery. X-ray photoelectron spectroscopy (XPS) has been used to study surface functionalization; surface topography changes related with the etching mechanism have been followed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and weight loss study. The results show a considerable improvement in surface wettability even for short exposure times, as observed by a remarkable decrease in contact angle values. The aging study shows a partial hydrophobic recovery due to the re-arrangement of polar species and migration of low molecular oxidized material (LMWOM). In addition to surface activation, SEM and AFM analyses show slight changes in surface topography as a consequence of the plasma-etching mechanism.

Plasma treatment is one of the methods currently used to obtain polymeric materials with surface properties appropriate to the functionality for which they were designed. However, the effects achieved after surface modification are not always long lasting and involve chemical and physical changes in the outermost layer. In this context, the effects of both argon and oxygen plasma on polylactic acid (PLA) films deposited on titanium were studied to determine which physical and chemical processes occur at the surface, and their duration. Regarding physical surface changes, there were scarcely any differences between both plasmas: roughness was very similar after treatments, root mean square height (Sq) being 10 times higher than the control, without plasma. Water contact angle (WCA) showed that the surface became more hydrophilic after application of the plasma, although hydrophilization was longer lasting in the case of argon treatment.

With regard to chemical changes, it was observed that the argon plasma treatment caused greater fragmentation of the polymer chains, and increased crosslinking between them. ToF-SIMS analysis made it possible to propose mechanisms to explain the formation of the fragments observed.

Low-temperature plasma treatment is a kind of environmentally friendly surface modification technology, which has been widely used to modify various materials in many industries. In this study, cold gas plasma was used to treat polypropylene (PP) fibres. The effects of plasma treatment on the surface morphology and wettability of the fibres were characterized using atomic force microscopy (AFM) and dynamic contact angle measurement. The AFM observations revealed the changes in the surface morphology of the fibres caused by plasma treatment. The dynamic contact angles (DCA) were measured based on the Wilhelmy principle. The DCA technique was able to examine the advancing contact angles and receding angles of the fibres. The study revealed that the plasma treatment could considerably reduce both advancing contact angle and receding angle of polypropylene fibre. The surface roughness was the main reason for reducing the receding contact angle, while the advancing contact angle was more related to the surface properties of the fibres.

A method to corona treat a polymeric surface with a fixed and pre-set treatment energy level is proposed. In order to reduce the effect of humidity, the Corona Discharge Energy – CDE value was controlled during the corona treatment by an in-line monitoring apparatus, which indicates when the energy level is attained. The method was tested applying a negative corona treatment discharge on a polypropylene copolymer film. Chemical and morphological surface changes were examined by IR spectra, contact angle and morphology. Treated samples show the presence of carbonyl, hydroxyl and unsaturations, the first being less concentrated. The formation of polar groups on the film surface led to a reduction of the contact angle and an increase in the surface tension. Film surface morphology was also modified, showing a second phase granular structure which grows with the increase of the CDE level.

In packaging, plastic films are very often applied as overprinting materials. The printing properties of plastic films depend on the value of the surface free energy. Usually, during storage but before printing, the surface free energy is decreasing as a result of ageing. The aim of this study was to analyse the influence of elevated temperature and UV radiation on ageing properties and variation of the free surface energy for three commercially available plastic films: polyethylene, polypropylene and polyethylene terephthalate. The investigation was done experimentally, and the surface free energy was calculated using two approaches, Owens-Wendt and van Oss-Chaudhury-Good. The time change of polar fractions was also analysed. The calculation results were compared and it was concluded that UV radiation causes more changes in surface free energy than elevated temperature. In some cases, surface free energy values calculated with the applied methods show similar trends.

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.

This paper presents a review of the ST and SFE values expressed in dyn/cm for a number of polymers, minerals, oxides and clays. The review also deals with the calculation of ST based on parachor values and other polymer properties obtained from a DIPPR database accompanied and coupled with QSPR software entitled TSAR. Data are also given on the ST of clays. The three components of the ST, the apolar Lifshitz–van der Waals component and the two polar (electron-donor and electron-acceptor) components of the various clays are also presented, as calculated by the van Oss et al. equation. Substitution of the cations in the innerlayer of clays by other inorganic cations is reviewed. Data are given on the effect of introducing organic ammonium cations into the clays and how they affect MMT, laponite, and talc. The effect of temperature on the ST of small molecules and on polymers is discussed, and a formula for this effect is shown. The effect of surface crystallinity on ST is discussed. The effect of chemical composition, structure and molecular weight are discussed as well. Systems for the estimation of ITs are reviewed, in relation to the ST values of the components. Data on the ST of high-energy materials are presented. The changes in these values upon interaction with low-energy surfaces are discussed. Copyright © 2005 John Wiley & Sons, Ltd.

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.

A new method for determining the surface tension of liquids has been derived. This involves the consideration of the advancing and receding contact angles of a liquid drop on a tilted solid surface. The theory has been tested by an improved optical projection technique for a variety of liquid/ solid systems and the results obtained are in agreement with the accepted values. It is shown that the advancing and receding contact angles are characteristic constants of liquid/solid system s and the calculated and measured values of the minimum receding angles are in agreement. The prevailing views of ‘hysteresis’ effects or ‘stationary’ contact angles which have arisen to account for the data available are incorrect and the discordant experimental results reported are due to inadequate technique. The difference between the adhesions corresponding to the advancing and receding angles is ascribed to the work done in removing an adsorbed unimolecular layer. The work done in gcal./mol. in forming this adsorbed layer is in reasonable agreement with that expected from studies in gas/solid systems and the forces involved are van der Waals’. Further, different solids that might be expected to show similar surface structures yield similar values for the work done. The variation in the value of the advancing angle in some liquid/solid systems and its constancy in others is reconciled with the polar character of the solid surface, i.e. it is suggested that short-range forces are involved. It has been found that monolayers of ferric stearate on glass are orientated with their hydrocarbon tails away from the interface in agreement with electron diffraction measurements. It is suggested that the methods may be useful for investigating the structure of monofilms and built-up layers of monofilms.

Corona treatment is commonly used in industry to enhance the surface-free energy of plastic films. However, corona treatment may cause some undesirable effects affecting further processing, such as sealing. In this paper, we deeply analyze the corona treatment effect on selected properties of various polymer films commonly used in packaging applications. The films were treated at two power levels (100 W and 300 W), and the experimental design included surface characterization and mechanical testing to assess changes in wettability, chemical structure, and seal strength. The Owens–Wendt approach confirmed the corona treatment effect by static contact angle measurement and surface free energy calculation. Next, their seal strength was evaluated in relation to surface energy and chemical structure changes. FTIR spectroscopy was used to identify functional groups potentially affected by corona treatment. The results indicate that the impact of corona treatment is material-dependent. In general, corona treatment at a lower level increases the seal strength, while corona treatment at a higher power level is related to a decrease in seal strength. The study highlights the importance of optimizing corona treatment parameters for specific materials to enhance seal performance without compromising surface integrity.

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.

Low-pressure plasma treatments in an rf discharge of O2 and Ar were employed to introduce polar functional groups onto the biaxial-oriented polypropylene (BOPP) surfaces to enhance the wettability and activation. The effects of plasma treatment on the morphology and wettability of the BOPP films were characterized using static contact angle measurements, attenuated total reflection (ATR)–FTIR spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). A clear increase in the surface energy of BOPP films due to O2 and Ar plasma treatments was observed. The surfaces became highly hydrophilic when exposed for 20 s or longer to the plasma discharge. The wettability of polymer surface can be improved when oxygen functionalities are generated, which can be achieved directly in O-containing plasmas or via post plasma reactions. Small reduction in surface energy of plasma treated BOPP films, after 30 days aging showed that the plasma-induced cross-linking in BOPP film was not the dominant phenomena. With increasing the treatment power and time, rate of the decrease in surface energy after aging is reduced. AFM and SEM images revealed distinct changes in the topography of BOPP due to O2 and Ar plasma treatments. Nodular structure is formed on the BOPP film during the treatment and the size of the nodules increases with the treatment time.

Plasticizer migration from plastics, particularly in polar polymers like flexible PVC, poses significant health risks, including endocrine disruption and carcinogenicity. This review article consolidates research on surface modification techniques aimed at suppressing plasticizer migration, which are crucial for minimizing health and environmental hazards. Over the past decade, substantial advancements have been made in this field. Physical irradiation methods, including plasma, ultraviolet, and gamma-ray irradiation—induce surface cross-linking, forming a three-dimensional network that reduces plasticizer migration by up to 80 %, as demonstrated by DEHP loss decreasing from 5.6 to 1.2 mg/cm2 in modified PVC. Chemical grafting techniques covalently attach hydrophilic groups or polymer chains, which interact with plasticizers via hydrogen bonding and van der Waals forces, achieving a 75 % reduction in migration, for example, DEHP leaching from 250 mg to 52 mg. Solution coating methods, particularly protein-based coatings, show exceptional performance with up to 93 % inhibition, reducing DEHP migration from 60 ppm to 4.2 ppm. Despite these achievements, challenges persist in enhancing coating durability, reducing costs, and minimizing environmental risks. Future research directions should focus on improving the long-term stability of coatings, refining experimental methodologies, and establishing robust evaluation standards. This work aims to provide a critical reference for the development of safer plastic applications in healthcare and food packaging industries, offering insights into the design and implementation of effective surface modification strategies to address the ongoing issue of plasticizer migration in plastic materials.

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.