The surface modification of synthetic fiber fabrics via corona discharge treatment and subsequent graft polymerization was investigated. Polyethylene (PE) nonwoven fabric and polyamide-6 (PA-6) nonwoven fabric were used as base fabrics. Acrylic acid (AAc) was graft polymerized onto the fabrics via corona discharge pre-treatment. The grafted amounts of PAAc were dependent on the grafting time, that of PA-6 being higher than that of PE. It was confirmed that the surface of the fibers constructing the fabric was fully covered with PAAc after the 20 min reaction. The surface of the PAAc grafted fabrics was characterized by X-ray photoelectron spectroscopy. The leakage of electrostatic charge from the fabric was determined and the dyeability was studied with methylene blue. The period of time in which the charge potential attenuated to 1/2 of the initial potential decreased drastically by grafting with PAAc. The grafted amount was enough for dyeing the entire fabrics.

Cold plasma treatments of polymers, dry processes, allow either the elaboration of hydrophilic or hydrophobic surfaces. For example, a poly(propylene) film treated in nitrogen plasma shows a surface having a hydrophilic and basic character since amino groups are attached onto the surface during the treatment. The treatment induces an increase of the surface tension of the polymeric material, which may be sometimes destroyed by an aging effect. For the treatment of poly(propylene) in nitrogen plasma, the aging is mostly due to a motion of attached groups from the surface to the bulk of the material and some oxidation of radicals formed during plasma treatment. The surface radicals formed and used for a post-reaction such as grafting are characterized in terms of chemical nature, density and reactivity.

The present invention provides a method of modifying the surface of a polymeric substrate, e.g., to improve the wettability of the polymer film surface and/or alter the reactivity of the surface of the substrate by further oxidation, comprising exposing the substrate to a flame. The flame is supported by a fuel and oxidizer mixture that includes an effective amount, for modifying the polymeric substrate, of at least one oxygen-containing compound that functions as a fuel substitute. Oxygen comprises between about 10 and 50 atomic percent of the compound. Large increases in the ASTM wetting test over that reported with conventional flame-treating processes, have been observed in films treated according to this invention. In addition, significant increases in polymer film surface oxidation levels have been observed.

This paper concerns the use of the low-pressure plasma process to confer an hydrophobic character to poly(acrylonitrile) films, without altering their bulk properties. Plasma based fluorination processes using saturated fluorine compounds such as CF₄, C₆F₁₄ and mixtures CF₄/H₂ were used. Such treated polyacrylonitrile films were characterized by XPS analysis, infrared (ATR) spectroscopy and contact angle measurements. The use of CF₄ led to the fluorination of the film surfaces. Indeed, XPS spectra showed the presence of -CHF-, -CF₂- and -CF₃ groups. Moreover, the contact angle θ which was 63° for untreated PAN films increased to 115°. Fluorine incorporation in the PAN disappeared when hydrogen is added to CF₄. In the case of treatment by C₆F₁₄, fluorination was accompanied by a polymerization, as evidenced by XPS with the disappearance of the N 1s photopeak corresponding to the C≡N functions in PAN. By considering the deposition of F- containing layer thickness, it was possible in this latter case to follow the surface modifications by ATR-i.r. spectroscopy

Corona discharge introduces polar groups into the polymeric surfaces and, as a consequence, improves the surface energy, wettability, and adhesion characteristics. The main chemical mechanism of corona treatment is oxidation. This article further discusses some special problems that are related to corona treatment of polyolefin films by reviewing the recent developments in this field, such as effect of corona treatment on adhesion, effect of resin additives on corona treatment, insufficient treatment and over-treatment of corona discharge, aging, and re-treatment. © 1999 John Wiley & Sons, Inc. Adv Polym Techn 18: 171–180, 1999
https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1098-2329(199922)18:2%3C171::AID-ADV6%3E3.0.CO;2-8

The effects of oxygen-plasma treatment of ultra-high-modulus polyethylene (UHMPE) fiber on the transverse properties of the UHMPE fiber/vinylester composites have been investigated. The UHMPE fiber/vinylester unidirectional (UD) laminates were prepared with untreated and oxygen-plasma-treated UHMPE fiber. The oxygen-plasma treatment of the UHMPE fiber increases the transverse tensile strength and failure strain of UHMPE-fiber/vinylester composites and changes the failure initiation site from the interface to the interior of the UHMPE fiber. The oxygen-plasma treatment of the UHMPE fiber introduced micro-pits on the fiber surface; these micro-pits improve the interfacial adhesion in UHMPE fiber/vinylester composites through the mechanical interlocking between the micro-pits and the vinylester resin. Finite-element (FE) modeling was performed to investigate the effect of the micro-pits on stress transfer in the UHMPE-fiber/vinylester composite. The micro-pits are known to increase the stress transfer from the vinylester resin to the UHMPE fiber and this increased stress transfer is correlated with the improved transverse properties and the transition of the failure initiation site after oxygen plasma treatment.

Currents during corona charging and surface potential decay after corona charging have been studied on polymeric films. As has been reported before, surface potential is a useful tool for investigating the electrical properties of an insulating material, making it possible to discriminate charge injection from polarization processes, when data are correctly analysed, and it has also been shown that, on thin polymeric films, slow polarization processes leading to heterocharge formation dominate at low fields, while charge injection occurs above a given field threshold. We present here a combined study of the surface potential after charge deposit and current flowing on the back electrode during the corona charge; we show that current measurements during the charge confirm the interpretation of potential measurements after corona charge. The outbreak of “hollows” in the potential distribution on the surface is clearly linked to the predominance of injected charge on the polarization charge. However, even at high fields, polarization phenomena will dominate again a given time after corona discharge stopping.

By now, the effect of microorganisms on polymer materials has been well studied. However, most of the investigations were aimed at polymer protection against biocorrosion or, on the contrary, biodegradation of polymer wastes. Using microbial treatment for polymer adhesion improvement was initiated only in the past decade. Nevertheless, such treatment, being a variant of chemical surface modification, has a number of advantages in comparison with other known treatment techniques: It needs no expensive chemicals and solvents. It is conducted at moderate temperatures and needs no energy expenditure. It is ecologically clean. Because of the great variety of existing microorganisms, it can offer the desired degree of treatment for different polymer materials.

The three states of matter are solid, liquid, and gas. A plasma state exists as its fourth state. A plasma consists of positively charged particles and negatively charged electrons existing at almost the same electrical density, it is overall electrically neutral, and it was named plasma by Langmuir in 1928. The easiest way to obtain a plasma state is to induce an electrical discharge in a gas. A corona discharge treatment is a kind of plasma treatment. Plasmas are classified roughly into two categories: equilibrium plasmas and nonequilibrium plasmas. In equilibrium plasmas, the temperatures of electrons and of the gas are the same. Mainly equilibrium plasmas have been studied, and temperatures of approximately 10,000 C have been reported. In nonequilibrium plasmas the gas is at ambient temperature, but the temperature of electrons is very high (about 10,000 C). These nonequilibrium plasmas are used in chemical applications and are called low-temperature plasmas or cold plasmas. The low-temperature plasmas are classified roughly into two categories:(1) ordinary low-temperature plasmas at low pressure and (2) corona discharges at atmospheric pressure. Ordinary low-temperature plasmas are widely used in chemical modification of the surfaces of materials, especially in semiconductor industries [1] as well as for polymers [2].

Good adhesion to polymers is required in a number of important technologies including adhesive bonding, printing, and painting. To achieve a satisfactory level of adhesion it is often necessary to pretreat the polymer by one of a wide range of methods. Two books are of particular interest [1, 2]. In the case of polar polymers such as nylon 66 and epoxide thermosets, a treatment may not be necessary, or if the surfaces are contaminated, a physical method such as solvent degreasing or grit blasting to remove the contaminants may be all that is required. On the other hand, if a polymer lacks suitable functionality, it will be necessary to modify its surface chemically. Polymers with no active functionality include low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP). A wide variety of methods for introducing new groups is available, including the use of low-pressure plasmas, corona discharges, flames, etchants, and active gases. Flame treatment to enhance adhesion to polymers has been used since the early 1950s, one of the first applications being to enhance print adhesion to lowdensity polyethylene. Since that time, flame treatment has been used with many other polymers in a variety of applications. Flame treatment has a number of advantages over the other main method of treating large areas of polymers, ie, the corona treatment. These include no reverse-side treatments, no creation of pinholes, no Ozone production, and better aging characteristics.

In recent years, we have witnessed a remarkable growth in the use of the synthetic organic polymers in technology, both for high-technology and for consumerproduct applications (see Fig. 1 [1]). Polymers have been able to replace more traditional engineering materials such as metals, because of their many desirable physical and chemical characteristics (high strength-to-weight ratio, resistance to corrosion, etc.) and their relatively low cost. However, fundamental differences between polymers and other engineering solids have also created numerous important technical challenges, which manufacturing operations must overcome. An important example is the characteristic low surface energy of polymers and their resulting intrinsically poor adhesion [2–6]; the term “adhesion,” as it is used here and elsewhere in this text, may be briefly defined as the mechanical resistance to separation of a system of bonded materials [7]. Because adhesion is largely a surface property, often governed by a layer of molecular dimensions, it is possible to modify this near-surface region without affecting the desirable bulk properties of the material.

The reversible work of adhesion (W) is the free energy change per unit area in creating an interface between two bodies (Fig. 1). The work W is related to the intermolecular forces that operate at the interface between two materials, eg, an adhesive and an adherend. However, in practice, the reversible work of adhesion may be obscured by other factors (eg, mechanical interlocking, interdiffusion) because it is always a few orders of magnitude lower than the measured adhesive joint strength [1, 2]. One important contribution to practical joint strength is the energy loss due to irreversible deformation processes within the adhesive. Nevertheless, Gent and Schultz [3] showed using peel strength measurements that viscoelastic losses were proportional to the reversible work of adhesion. For this reason, one of the important tasks is to determine the nature of interfacial chemical and physical forces and to understand how they control the reversible work of adhesion.

Several techniques have been applied for the characterization of three PET films surfaces: homopolymer PET film, corona treated PET film and a poly(ethylene terephthalate‐co‐1,4‐cyclohexanedimethanol) film. The objective of this work is to investigate and to apply precise and mutually complementary techniques which give detailled information about theses surfaces, as there are few papers with global and conclusive results. The film surfaces were investigated to support the development of new products and envisage new apllications to the existent films. Scanning electron micrographs, attenuated total reflection Fourier transform infrared spectroscopy (FTIR‐ATR) and multiple internal reflection Fourier transform infrared spectroscopy (FTIR‐MIR) spectra show that the chemical composition, topography and surface roughness of the films are different. The corona‐treated PET film shows high surface tension value due to the major contribution on the polar groups and oxidation level acquired. The copolyester film is much less crystalline than the other films analyzed, as demonstrated by refractive index measurements and X‐ray photoelectron spectroscopy (XPS). The amorphous structures obtained and the high tension level of the corona‐treated films provide a better understanding of the adhesion phenomena. In view of results obtained, one can assume that corona treated films owing to its higher surface tension and films with CHDM owing to its surface amorphization should provide manufacturing industries better processing conditions than films without surface treatment and also higher levels of adhesion to paints and coatings.

Modification of polyolefin surfaces is often necessary to achieve improved printability, lamination, etc. Although corona discharge and flame treatments can produce the higher surface energy needed for these applications, the properties of the resulting surfaces are not always optimal. Atmospheric pressure plasma is a surface modification technique that is similar to corona discharge treatment, but with more control, greater uniformity, and higher efficiency. Using an atmospheric pressure plasma unit with a dielectric barrier discharge generated using an asymmetric pulse voltage, the effects of different gases, powers, and linespeeds on polyethylene surface treatment were studied. Our results show that atmospheric pressure plasma can be used to achieve higher long-term wettability, higher surface oxygen and nitrogen, and a greater range of surface chemistries with better robustness versus standard corona treatment. Atomic force microscopy results suggest significant differences in the mechanism of surface functionalization versus etching and ablation depending on the gases used. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 319–331, 1999
https://onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291097-4628%2819990110%2971%3A2%3C319%3A%3AAID-APP16%3E3.0.CO%3B2-T

Corona discharge treatment was conducted for ultrahigh molecular weight polyethylene (UHMWPE) fiber. The functional groups and surface roughness of the polyethylene fiber surface were determined by an X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The interfacial shear strength of UHMWPE fiber with HDPE film was determined by microbond pullout method. The interfacial shear strength increased by corona treatment. Then, the effect of the chemical and physical factors on the interfacial shear strength was discussed based on the results of multivariate regression analysis. The results indicated that the contribution of functional groups and surface roughness to the interfacial shear strength was expressed as 50 and 50%, respectively. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 243–249, 1999
https://onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291097-4628%2819990110%2971%3A2%3C243%3A%3AAID-APP7%3E3.0.CO%3B2-I

Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle analyses were performed on unsized and sized carbon fibers to better understand the mechanism of adhesion in carbon fiber/polymer matrix composites. AFM images and surface roughness analyses showed that the sizing changes the surface topography on a microscopic scale. The total surface energy decreased from 70 mJ/m² for unsized fiber to 54 mJ/m² for Ultem® sized and to 36 mJ/m² for PTPO sized fibers. The percentage of functional groups on the sized fibers decreased slightly compared to the unsized fibers. The surface functional groups and surface energies of fibers are critical properties in predicting fiber/matrix adhesion. Angle dependent XPS, voltage contrast XPS, and perimeter measurements revealed that the thickness of the poly(thioarylene phosphine oxide) (PTPO) sizing on the carbon fiber surface was greater than for the poly(etherimide) (Ultem®) sizing.

The efficacy of vacuum ultraviolet irradiation for oxidizing the surface of cellulose fibers was compared to that of the conventional wet and dry processes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 357–361, 1999
https://onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291099-0518%2819990201%2937%3A3%3C357%3A%3AAID-POLA13%3E3.0.CO%3B2-2

Polyvinylidenefluoride (PVDF) was irradiated by a keV Ar⁺ ion in O₂ environment for improving adhesion between PVDF and Pt, and reaction between PVDF and the ion beam has been investigated by X-ray photoelectron spectroscopy (XPS). The adhesion test between Pt and the modified PVDF was carried out by boiling test, in which the specimens were kept in boiling water for 4 h. Two failure modes (buckling up due to weak adhesion and crack formation due to strong adhesion) of Pt films have been observed in the system. Contact angle of PVDF was reduced to 31 from 75° by the irradiation of 1 × 10¹⁵ Ar⁺ ions/cm² with oxygen flow rate of 8 sccm. The surface of the irradiated PVDF became more rough as ion dose increased. The improved adhesion mechanism and identification of newly formed chemical species have been confirmed by Carbon 1s and Fluorine 1s X-ray photoelectron core-level spectra. The main reaction occurred at the irradiated PVDF surface is an ion-beam-induced oxidation accompanied with preferential sputtering of fluorine. Newly formed chemical species at interface are regarded as ester and carboxyl groups. Adhesion of the Pt–PVDF interface was improved by ion irradiation in O₂ environment. This improvement is originated from the presence of carbon—oxygen bonds on the irradiated PVDF surface. Comparison of failure modes on the irradiated PVDF at various conditions after the boiling test shows that adhesion of Pt film is largely affected by the product of ion-assisted reaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 41–47, 1999
https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1097-4628(19990404)72:1%3C41::AID-APP4%3E3.0.CO;2-J

The deposition of plasma polymers on poly(acrylonitrile) (PAN) fibers has been investigated by X-ray photoelectron spectroscopy and dynamic contact angle measurements. Four polymerizable monomers were examined: tetrafluoromethane (TFM), perfluoropropene (PFP), tetramethyldisiloxane (TMS), and hexamethyldisiloxane (HMS). The deposition rate of TFM was undetectable and the treated fibers exhibited some fluorination and an increase of hydrophilicity, due to posttreatment oxidation after exposure to air. The deposition rate of PFP was quite slow and the formation of an incomplete fluorinated layer was observed, with a remarkable increase of the water advancing contact angles. TMS and more so HMS quickly formed continuous and reproducible polysiloxane layers having pronounced hydrophobic properties. The influence of the position of the fibers in the plasma reactor chamber was also investigated. A good uniformity of deposition was found when the fibers were placed at different points between the electrodes.

To analyze various approaches for the determination of surface free energies of solids from liquid-solid contact angles, comb-like polymers with controlled grafting rates and macromolecular structures have been synthesized. The surface free energy parameters were calculated from the contact angles of standard liquids on the solid surfaces. A mathematical approach of the so-called acid-base theory of adhesion was used to characterize the nucleophilic and/or electrophilic behavior of the polymeric solid surfaces. Thus, correlations were established between the macromolecular structures and the dispersive component of the surface free energy, on the one hand, and the acid and base components, on the other. The main conclusion is that the surface free energy components are relevant for the characterization of functional comb-like polymeric materials: the dispersive and base components increase with the number of grafted electron-donating groups, whereas the acid component decreases.

The modifications induced by excimer laser irradiation of poly(ether ether ketone) (PEEK) surfaces have been investigated as a function of the laser process parameters for laser fluences below the material ablation threshold. In the case of 193 nm laser treatment, a significant increase in the adhesion properties of PEEK was obtained due to the formation of new polar and reactive groups on the surface. The extent of these reactive groups has to be controlled since their presence in high concentration may also have a negative effect on the mechanical properties of the treated surface. Laser treatments using 248 nm radiation did not result in a significant increase in the adhesion properties of PEEK. This probably results from thermal degradation of the surface at this laser wavelength.

The effects of intense pulsed high power ion beam (HPIB) treatment of ultra-high strength polyethylene (UHSPE) fibers on the fiber/epoxy resin interface strength were studied. For this study, argon ions were used to treat Spectra^™ 1000 (UHSPE) fibers in vacuum. Chemical and topographical changes of the fiber surfaces were characterized using Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), dynamic wettability measurements, and scanning electron microscopy (SEM). The fiber/epoxy resin interfacial shear strength (IFSS) was evaluated by the single fiber pull-out test. The FTIR-ATR and XPS data indicate that oxygen was incorporated onto the fiber surface as a result of the HPIB treatment. The wettability data indicate that the fibers became more polar after HPIB treatment and also more wettable. Although the total surface energy increased only slightly after treatment, the dispersive component decreased significantly while the acid-base component increased by a similar amount. SEM photomicrographs revealed that the surface roughness of the fibers increased following the HPIB treatment. The single fiber pull-out test results indicate that HPIB treatment significantly improved the IFSS of UHSPE fibers with epoxy resin. This enhancement in IFSS is attributed to increased roughness of the fiber surface resulting in mechanical bonding and in increased interface area, increased polar nature and wettability, and an improvement in the acid-base component of the surface energy after the HPIB treatment.

Polytetrafluorethylene (PTFE) was treated with N⁺ , O⁺ and C⁺ ion beams with energies of 20 and 30 keV at 5 mA/cm² current density in the pulse regime. Structural changes were studied by IR ATR, XPS, IR diffuse reflectance spectra and wetting methods. After treatment the PTFE surface became chemically active to isocyanate, acrylamide and epoxy reagents, which caused a change of interface interaction with active adhesives. The durability of the PTFE adhesion joint to an epoxy adhesive increases by more than 100 times. The ion beam treatment can be used to increase adhesion joint durability of PTFE.