The surface modification of poly(vinylidene fluoride) (PVDF) film induced by remote Ar, H₂, and O₂ plasmas have been investigated using contact angle measurement, X-ray photoelectron spectroscopy, and scanning probe microscope. The contact angle of water shows an improvement in the PVDF surface wettability during short plasma exposure time. Three remote plasmas treated PVDF sheet surfaces occurred dehydrofluorination and oxidation reactions simultaneously. Remote hydrogen plasma was the most effective in defluorination reactions and remote oxygen plasma was unfavorable to abstract fluorine atoms.

The capacity of a cold atmospheric-pressure air plasma (CAAP) device for advanced first aid is presented. Using swine as an animal model, two trials: 1) a large, curved cut in hindquarters area and 2) amputation of a front leg, were performed. Cold atmospheric-pressure air plasma effluent, which carries reactive oxygen species (ROS) atomic oxygen (OI), is applied for wound treatments. Swift hemostasis of the wounds by the CAAP treatment was demonstrated. The pressure applied by a finger on the cut arteries in trial 1 and the tourniquet applied in trial 2 could be removed immediately after the treatment and there was no re-bleed in both cases. CAAP hemostasis mechanism was explored via in-vitro tests. The tests on sodium citrate mixed blood-droplet samples show that 1) the heat delivered by the CAAP has no impact on the observed clot formation, 2) plasma effluent activates platelets to promote coagulation state and cascade, and 3) the degree of clotting increases with the total amount of applied OI by means of the CAAP effluent. It took only 16 s of the CAAP treatment to reach full clotting, which was considerably shortened from the natural clotting time of about 25 minutes. The tests on smeared blood samples show that the reduction of the platelet count and the increase of RBC count are proportional to the amount of applied OI. A plausible CAAP hemostasis mechanism is concluded from the in vitro test results and the animal model trials.

Commercial polyvinylchloride (PVC) sheets were treated by plasma immersion ion implantation, PIII. Samples were immersed in argon glow discharges and biased with 25 kV negative pulses. Exposure time to the bombardment plasma changed from 900 to 10,800 s. Through contact angle measurements, the effect of the exposure time on the PVC wettability was investigated. Independent of t, all samples presented contact angles, θ, equal to zero after the treatment. However, in some cases, surface hydrophilization was not stable, as revealed by the temporal evolution of θ. Samples bombarded for shorter periods recovered partially or totally the hydrophobic character while the one exposed for the longest time stayed highly hydrophilic. These modifications are ascribed to the Cl loss and O incorporation as shown by XPS measurements. Furthermore, the mobility of surface polar groups and the variation in the cross-linking degree can also affect the PVC wettability.

The comparison of corona-treated and flame-treated polypropylene (PP) films provides insight into the mechanism of these surface-oxidation processes. Atomic force microscopy (AFM), contact-angle measurements, and X-ray photoelectron spectroscopy (XPS or ESCA) were used to characterize surface-treated biaxially oriented PP. While both processes oxidize the PP surface, corona treatment leads to the formation of water-soluble low-molecular-weight oxidized materials (LMWOM), while flame treatment does not. Computational modeling of the gas-phase chemistry in an air corona was performed using a zero-dimensional plasma-chemistry model. The modeling results indicate that the ratio of O to OH is much higher in a corona discharge than in a flame. Chain scission and the formation of LMWOM are associated with reactions involving O atoms. The higher ratios of O to OH in a corona are more conducive to LMWOM production. Surface-oxidized PP exhibits considerable thermodynamic contact-angle hysteresis that is primarily caused by microscopic chemical heterogeneity.

A corona discharge treatment of low-density polyethylene film (LDPE) was carried out in preparation for flexographic printing. Such treatment of the PE film is necessary if maximum adhesion of ink is to be achieved. This project involved three different treating machines for which the current had to be manipulated in all the machines so that a standard treatment could be accomplished. Using a mathematical relation, current requirements for each machine were calculated and used to standardize treatment level of PE films. Standardization was achieved by controlling input current in all the three machines so as to attain a treatment level of 38 dynes/cm. This level of treatment showed the best results in adhesion of ink to the PE film during printing. The exercise also confirmed that printing must be carried out within 24 h of treatment since the level of treatment deteriorates with time.

Surface potential decay after negative corona charge deposition has been studied for polypropylene films 50μm thick, over a wide range of decay times and charging voltage (500–2800V). At low initial potential (500–800V), the surface potentials were stable and did not decay. At high initial potential (1200–2800V), the surface potential decay has been clearly observed with differences in the decay rate. The observed decay behavior has been computer simulated to elucidate the transport mechanism in polypropylene films. A good agreement between measured and calculated decay curves was obtained with a model in which charges are transported by hopping of injected carriers between localized trapping centers. The model is characterized by parameters such as the free carrier mobility, the mean free time of carrier between traps and the mean capture time in trap. The transport parameters have been determined by a fitting procedure.

A series of low-density polyethylene (LDPE) surfaces, chemically modified using a number of oxidative techniques employed for adhesion enhancement (pretreatments), have been studied by time-of-flight (ToF) SIMS and XPS. The methods consisted of corona discharge, flame, electrochemical, chromic acid, acid dichromate and acid permanganate treatment. All except flame treatment were performed under mild and fairly severe conditions to yield a range of surface chemistries. The XPS analysis, using high energy resolution and a refined approach to C 1s curve-fitting, provided some new insights into the quantitative assessment of the type and concentration of functional groups. Both positive and negative ion ToF-SIMS spectra were obtained at high mass resolution. The oxygen-containing fragments were identified by accurate mass analysis and subjected to a detailed comparison with the XPS results. No convincing relative intensity correlations could be identified that would allow particular secondary ion fragments to be associated strongly with particular functional groups (in this multi-functional surface situation). Inorganic residues resulting from wet chemical treatments were also investigated and here the two techniques were found to be more complementary. Copyright © 2003 John Wiley & Sons, Ltd.
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/sia.1515

Polyester fabric was treated by corona discharge irradiation at different voltages. The treated fabric showed increased wicking and hydrophilic properties and the properties can be preserved for a long time. Dyeing of the treated fabric showed that dyeing speed and the dye-uptake were improved. Surface affinity between the treated fabric surface with modified starch sizing was also confirmed to be increased. This is generally useful for the sizing of polyester staple yarn and the polyester fabric dyeing. All the results are supposed due to the improved hydrophilic properties produced by the corona discharge treatment.

The surface characteristics of polymers are important factors determining their interfacial properties and their technological performance. Changes in physical and chemical properties of a polymer film may be induced by subjecting the material to a variety of surface modification techniques, one of which is ion-beam modification. In order to understand the underlying mechanisms X-ray photoelectron spectroscopy (XPS) was used to study the alterations of the polystyrene (PS) surface after Ar-ion treatment under well controlled conditions with low ion doses from 10¹² to 10¹⁶ cm^-2. The ion bombardment leads to surface functionalization, loss of aromaticity, and free radical formation. Induced surface cross-linking and the formation of polar groups raised the surface glass transition temperature of PS film.

Polystyrene, a polymer extensively used in the biomedical field, causes a problem for some applications because of its surface hydrophobicity. Nitrogen plasma could transform this shortage through polar group attachment. To understand the role of hydrogen during surface functionalization in the nitrogen cold plasma, the effects of the nitrogen and the mixture of N₂/H₂ plasma are investigated by both the examinations of the densities of attached amine groups and the in-situ diagnostic analyses such as optical emission spectroscopy and mass spectrometry. An increase of functionalization has been proved to be controlled by the gaseous NH radical formation when H₂ is added.

The effectiveness of the treatment with ultraviolet light (UV) on several polymeric surfaces has previously been established. In this study, a low pressure mercury vapour lamp was used as a source of UV radiation for the surface treatment of a difficult-to-bond block styrenebutadiene-styrene rubber (S6), the treatment time ranging from 10 s to 30 min. The UV-treated S6 rubber surfaces were characterized by contact angle measurements (ethylene glycol, 25°C), ATR-IR spectroscopy, XPS, Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). T-peel tests on UV-treated S6 rubber/polyurethane (PU) adhesive/ leather joints (before and after ageing) were carried out to quantify adhesion strengths. The UV treatment of S6 rubber produced improved wettability, the formation of CO, CO and COO moieties, and ablation (removal of a thin rubber layer from the surface). The extent of these modifications increased with increasing treatment time. The extended UV treatment produced greater surface modifications, as well as the incorporation of nitrogen moieties at the surface. Furthermore, noticeable ablation of S6 rubber surface occurred. Peel strength values increased with increased treatment time of UV treatment of S6 rubber. Also, with increasing treatment time, the adhesive joints showed different loci of failure: adhesional failure for the as-received and 2 min-UV treated S6 rubber/polyurethane adhesive/leather joints changed to mixed failure (cohesive in the treated S6 rubber + adhesional failure) for the 30 min-UV treated S6 rubber/polyurethane adhesive/leather joint.

One of technologically imminent problems related to the use of pressure sensitive adhesives (PSAs) in the LCD industry is how to properly control the surface properties of various polymeric films used in devices to obtain sufficient bond strength with PSAs. To provide practical solutions to this issue, we used two types of surface treatments, NaOH and corona, to control the surface properties of polymeric films that are widely used in the LCD industry. Here we report a significant increase in surface tension in triacetyl cellulose (TAC) and discotic liquid crystal (D-LC) films along with a remarkable enhancement of bond strength in TAC/PSA and D-LC/PSA systems. The major portion of surface tension increase, in both types of films, was found to be due to an increase of polar component. The continuous increase of OH functionality in TAC with NaOH treatment time supported this observation. Furthermore, we established a map of surface treatment by studying the sequential effects of the two treatments, and based on this, we clearly demonstrated that each treatment had its own limiting value that could not be altered regardless of the sequence of surface treatment.

Ethylene-co-tetrafluoroethylene copolymer (ETFE) films were modified by four plasmas: direct and remote H2 plasmas and direct and remote O2 plasmas; and the hydrophobic recovery process of these plasma-modified surfaces was investigated using water contact angle measurements and angular XPS. The water contact angle measurements showed important aspects for the hydrophobic recovery process. (1) All plasma-modified ETFE surfaces, regardless of the kind and mode of plasmas, showed increases in the contact angle with increasing aging time. The increase continued for 5 days after finishing the plasma modification, and stopped after 5 days. (2) The plasmamodified surfaces after the aging process never reverted back to the same level of the contact angle as for the unmodified (original ETFE) surfaces. (3) The contact angle after the aging process was strongly dependent on to what plasma the ETFE surfaces were exposed in the modification. (4) The aging temperature influenced the contact angle value after the aging process. The angular XPS measurements also provided a detailed description of the chemical composition of the topmost layer. (1) The chemical composition at the topmost layer of the surfaces altered during the aging process. (2) CH₂-CH₂-CHF, and CH₂-CHF-CH₂ and CH₂-CH(OH)-CF₂ groups disappeared from the topmost layer during the aging process; and CH₂-CH₂-CH₂, and CH₂-CH₂-CF2 and CH₂-CH(OH)-CHF groups appeared at the topmost layer. (3) Such disappearance and appearance occurred on all plasma-modified surfaces regardless of the kind (H₂ or O₂ plasma) or mode (direct or remote plasma) of plasmas used for the modification. This may be due to segmental mobility of CH₂-CH₂-CH₂ sequences rather than of CF₂-CF₂-CF₂ sequences.

The acid-base theory as developed by van Oss, Chaudury and Good is a powerful tool to analyze the surface free energy of polymeric materials; however, some problems are encountered in its application and some authors have shown that these problems can be theoretically solved considering this theory as an example of the so-called LFER theories. From this point of view, the definition of a well-defined scale of acid-base strength and the use of a wide and well-equilibrated, appropriate set of liquids is very important. In the present paper some recent results are presented which are based on the mathematical approach discussed by Della Volpe and Siboni in previous papers. The treatment is developed as a list of questions, Frequently Asked Questions (FAQs), whose theoretical implications are discussed using numerical examples chosen from the literature. Some literature data, collected by the opponents of the acid-base theory and recently published, are re-analysed using these methods, showing that they constitute a well-defined set to calculate, with a good precision, the acidbase components of the considered materials and the interfacial energies of liquids used. The present paper is the premise of a second one, in which a set of contact angles data collected by the authors and by other researchers will be analysed following the principles discussed here.

The effect of ion implantation including ion species (N₂ and C₃H₈⁺) and the fluences (1x10¹⁴-5x10¹⁵ ions/cm²) on the surface energy of ultrahigh molecular weight polyethylene (UHMWPE) were investigated. The total surface energy increases significantly after implanting with the fluence of 1x10¹⁴ ions/cm² regardless of ion species, then, the total surface energy slightly increases for N₂⁺ implanted UHMWPE and decreases slightly for C₃H₈⁺ implanted UHMWPE with a further increase of fluence. The structural changes of UHMWPE with different fluence for different ion species are very similar. The linear chains of UHMWPE are damaged and cross linking is generated after implantation. As the fluence increases, the polymer surface becomes more disordered, and the surface becomes hydrogenated amorphous carbon when the fluence exceeds 1x10¹⁵ ions/cm². The surface roughness increases with the increase of the fluence regardless of ion implantation species.

Plasma treatment of polymers encompasses a variety of plasma technologies and polymeric materials for a wide range of applications and dates back to at least the 1960s. In this article we provide a brief review of the United States patent literature on plasma surface modification technologies and a brief review of the scientific literature on investigations of the effects of plasma treatment, the nature of the plasma environment, and the mechanisms that drive the plasma–surface interaction. We then discuss low‐radio‐frequency capacitively coupled nitrogen plasmas and their characteristics, suggesting that they provide significant plasma densities and populations of reactive species for effective plasma treatments on a variety of materials, particularly when placing the sample surface in the cathode sheath region. We further discuss surface chemical characterization of treated polymers, including some results on polyesters treated in capacitively coupled nitrogen plasmas driven at 40 kHz. Finally, we connect plasma characterization with surface chemical analysis by applying a surface sites model to nitrogen uptake of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) treated in a 40 kHz nitrogen plasma. This example serves to suggest an interesting practical approach to comparisons of plasma treatments. In addition, it suggests an approach to defining the investigations required to conclusively identify the underlying treatment mechanisms.

The treatment of elastomer articles in a low-temperature glow-discharge plasma in fluorinated organics is an effective method for the enhancement of their wear resistance without changing the formulation of rubbers. As a result of plasma-assisted deposition on an elastomer of a fluorinated antifriction film chemically bound to the substrate, the elastomer friction coefficient is considerably decreased, sticking to a counterface is prevented, and the wear resistance of the elastomer is enhanced, retaining their bulk properties. Based on the study of the structure of the antifriction film at different modification stages and its transformation during friction, a conclusion on the mechanism of elastomer surface failure under dynamic friction conditions was made.

In this paper are discussed some of the fundamental principles which are relevant to an understanding of the influence that interfacial roughness may have on adhesion. The surface energies of the adhesive, substrate and of the interface between them determine the extent of wetting or spreading at equilibrium. Numerical values for surface energies may be obtained either from contact angle measurements or from analysing force–displacement curves obtained from the surface forces apparatus. The extent to which the relationships, appropriate for plane surfaces, may be modified to take into account interfacial roughness are discussed. For modest extents of roughness, the application of a simple roughness factor may be satisfactory, but this is unrealistic for many of the practical surfaces of relevance to adhesive technology which are very rough, and is ultimately meaningless, if the surface is fractal in nature. Some examples are discussed of published work involving polymer–metal and polymer–polymer adhesion, where the roughness of the interface exerts a significant influence on the adhesion obtained. Roughness over a range of scales from microns to nanometres may strengthen an interface, increasing fracture energy by allowing bulk energy dissipating processes to be activated when the bond is stressed.

Poly(tetrafluoroethylene-co-perfluoro [alkyl vinyl ether]) (PFA) and polytetrafluoroethylene (PTFE) films were treated by three kinds of atmospheric pressure glow plasmas: an untreated sample was treated by He plasma or trimethoxyborane (TMB)/H₂/He plasma, and a TMB-absorbed sample was treated by H₂/He plasma. TMB was a new reactant for the treatment, to increase the films’ adhesive strength with an epoxy glue. These films were also treated by a wet method using a sodium solution (Tetra-Etch compound) and such films were used as the control samples. The peel strength values of the controls of PFA and PTFE were 3.5 and 9.5 N cm⁻¹, respectively. The adhesive strengths of all plasma-treated PFAs were stronger than those of untreated one. Especially, the peel strength of the TMB/H₂/He plasma-treated PFA showed the maximum value of 4.5 N cm⁻¹, which was bigger than that of the control one. The adhesive strength of the TMB/H₂/He plasma-treated PTFE films also showed the maximum peel strength, 7.9 N cm⁻¹, but this value did not exceed that of the control PTFE. Such results suggested that the TMB/H₂/He plasma had the advantage of providing better adhesive improvement of those polymers, especially PFA than the wet method could provide. The results of XPS and SEM indicated that TMB actively removed fluorine atoms from the polymer surface. Therefore, boron compounds are effective for the improvement of the adhesive strength between the fluorinated polymer and the epoxy glue.

A styrene-butadiene-styrene (S6) rubber was treated with corona discharge to increase its surface energy and adhesion to polyurethane (PU) adhesive. The influence of the length of treatment (the speed of the upper plate was varied from 80 to 900cm/min) during corona discharge was analyzed. The corona energy applied to S6 rubber surface ranged from 0.4 to 4.6J/cm ² . The surface modifications produced as a consequence of the corona discharge were characterized immediately after treatment was carried out and were monitored by means of different surface analysis techniques, mainly contact angle measurements (ethylene glycol, 25 ^o C), ATR-IR spectroscopy, XPS and Scanning Electron Microscopy (SEM). T-peel tests of corona-discharge-treated S6-rubber/polyurethane (PU) adhesive/leather joints (72h after joint formation) were carried out to evaluate the influence of the surface modifications produced by the corona discharge on the adhesion properties of the treated S6 rubber.The corona discharge improved the wettability of the S6 rubber due to the formation of polar moieties, mainly C-O, C=O and COO ^- groups. These chemical modifications were not detected by ATR-IR spectroscopy (depth of analysis about 5μm), indicating that a nanometer-range oxidized layer was created on the S6 rubber surface by treatment with corona discharge. Besides, surface cleaning and removal of rubber contaminants (mainly silicon moieties) were produced but roughness was not created as a consequence of the treatment. These modifications were enhanced when a low speed treatment (long treatment and high corona energy) was carried out. Peel strength values of corona-discharge-treated S6 rubber/PU adhesive/leather joints only moderately increased (mainly for long length of the corona discharge). Although corona treatment chemically modified the surface of the S6 rubber, the absence of surface roughness might likely be responsible for the slight improvement in its adhesion properties.

In order to investigate the effect of atmospheric pressure plasmas on adhesion between aramid fibers and epoxy, aramid fibers were treated with atmospheric pressure helium/air for 15, 30 and 60 s on a capacitively-coupled device at a frequency of 5.0 kHz and He outlet pressure of 3.43 kPa. SEM analysis at 10 000× magnification showed no significant surface morphological change resulted from the plasma treatments. XPS analysis showed a decrease in carbon content and an increase in oxygen content. Deconvolution analysis of C1s, N1s and O1s peaks showed an increase in surface hydroxyl groups that can interact with epoxy resin. The microbond test showed that the plasma treatment for 60 s increased interfacial shear strength by 109% over that of the control (untreated). The atmospheric pressure plasma increased single fiber tensile strength by 16-26%.

In this paper, we report and discuss a surface treatment method, using a dielectric barrier discharge (DBD) of random filamentary type. This offers a convenient, reliable and economic alternative for the controlled modification (so far, largely dependent on surface oxidation) of various categories of material surfaces. Remarkably uniform treatment and markedly stable modified surface properties result over the entire area of the test surfaces exposed to the discharge even at transit speeds simulating those associated with continuous on-line processing. The effects of air-DBD treatment on the surfaces of various polymer films and polymer-based fabrics were studied. The dielectric barrier concerned has been characterized in terms of the energy deposited by the discharge at the processing electrodes and the resultant modifications of the surface properties of the treated samples were investigated using x-ray photoelectron spectroscopy, contact angle/wickability measurement and scanning electron microscopy. The influence of the surface treatment parameters, such as the energy deposited by the discharge, the inter-electrode gap and the treatment time were examined and related to the post-treatment surface characteristics of the materials processed. Relationships between the processing parameters and the properties of the DBD treated samples were thus established. Of the three process variables investigated, the duration of the treatment was found to have a more significant effect on the surface modifications found than did the discharge energy or the inter-electrode gap. Very short air-DBD treatments (fractions of a second in duration) markedly and uniformly modified the surface characteristics for all the materials treated, to the effect that wettability, wickability and the level of oxidation of the surface appear to be increased strongly within the first 0.1–0.2 s of treatment. Any subsequent surface modification following longer treatment (>1.0 s) was less important. The modification of the surface properties also appears to be stable with time, as minimal recovery of the surface properties is shown on ageing post-treatment. The behaviour of the woven textile polymers examined was found to be very similar, under DBD treatment, to that of thin-film variants based on the same polymers. For the porous textile fabrics examined, rapid and efficient treatment (fractions of a second) on both sides of the treated samples was found to be ensured. Thereby the system regime used offers the attractive prospect of controlling the modification of non-compact materials of various texture, porosity, etc. The DBD described system thus provides a chemically mild and mechanically non-destructive means of altering surface properties targeting improved surface characteristics and potentially better application performance.

The effects of low-molecular-weight oxidized materials generated by corona treatment on the adhesion properties of polypropylene (PP) film were investigated by adhering four different materials to the modified PP: a polyamide printing ink, vapor-coated aluminum, a synthetic-rubber pressure-sensitive adhesive, and an acrylate-based pressure-sensitive adhesive. The low-molecularweight materials enhanced the adhesion of the ink and acrylate-based material, but hindered the adhesion of the metal and the rubber-based adhesive. This seemingly contradictory adhesion behavior can be readily explained using the principles outlined by Brewis and Briggs in the 1980s.

The flame treatment of polypropylene (PP) film involves the use of impinging, conical flames to oxidize the surface of the PP. Depending on treatment conditions, the PP film can be exposed to an inhomogeneous environment because of the conical shape of the flames. This environment can lead to cross-web variations, or 'lanes', in the wettability of the film. We have developed a simple method to quantify these non-uniformities using the information provided by the Wilhelmy plate technique of dynamic contact angle measurement. Both surface-averaged and spatially resolved surface-energy data can be obtained by this technique. In the case of our PP film, the spatial nonuniformities were found to be caused by variations in surface chemistry, not topography. These nonuniformities are not observed on untreated PP. Use of this method enables a quantitative evaluation of the effects of flame-treatment process variables on treatment uniformity.

Oriented polypropylene treated by atmospheric barrier discharges in air and nitrogen was investigated using several techniques: contact angle measurements, ATR-FT-IR spectroscopy and two adhesion tests based on the stripping of an applied ink layer. The activation in an air discharge was found to be much weaker compared to the activation in industrial grade nitrogen, particularly with respect to adhesion. The adhesion was found to be much better in nitrogen in spite of the common use of air in industrial 'corona discharges'. A new 'abrasive shear-stripping' (AS) test for ink coating adhesion was designed and performed. It was shown that the AS test was much more sensitive than the classical adhesive tape test and was sensitive enough to monitor ageing and overtreatment. The contact angle measurements did not correlate completely with the adhesion properties and could not monitor the overtreatment, while the ATR-FT-IR technique indicated changes just for overtreated foils.

Ethylene vinyl acetate (EVA) material containing 20 wt% vinyl acetate (EVA20) was treated with corona discharge to improve its adhesion to polychloroprene adhesive. Several experimental variables in the corona discharge treatment of EVA20 were considered: corona energy, type of electrode, and number of consecutive treatments. Advancing contact angle measurements (water, 25°C) showed an increase in the wettability of EVA20 after treatment with corona discharge, which corresponds to an increase in the O/C ratio on the treated surface. The higher the corona energy (i.e. the higher discharge power and longer treatment times), the greater the degree of surface oxidation. Peel strength values of the joints produced with EVA20 using a polychloroprene adhesive containing 5 wt% isocyanate increased from 1.5 kN/m (as-received EVA20) to 4.3 kN/m (corona-treated EVA20). A mixed (adhesional + cohesive in EVA20) locus of failure was obtained in all adhesive joints produced with corona discharge-treated EVA20. Finally, the number of consecutive corona discharge treatments and the surface area of the electrode (spherical versus hook-shaped electrode) did not greatly influence the adhesion of EVA20 to polychloroprene adhesive.

In order to explore the fundamental mechanism of paint adhesion to polymer substrates the surface of polypropylene- ethylene propylene rubber (PP-EPR) blends was modified by flame or plasma treatments. The changes in surface composition and properties were investigated and discussed in light of the results of simple adhesion tests. The topography and surface properties of the PP-EPR samples were studied by employing various surface sensitive techniques. Additionally, the surface properties of the pre-treated PP-EPR were compared with the model polymers poly(methyl methacrylate) (PMMA) and polycarbonate (PC) displaying a poor and an excellent paint adhesion, respectively. Differential scanning calorimetry (DSC) measurements showed that the miscibility of the polymer substrate with paint components was an essential factor for the understanding of the adhesion mechanism. A general model of paint adhesion to polymer surfaces is proposed, where the degree of interdiffusion of the polymer chains of the substrate and paint in the interphase determines the adhesion strength.