Surface Treatment Of Polymers Research Articles

Cementitious composites reinforced with continuous carbon fibres for strengthening of concrete structures

“Continuous fibre wrapping technique” is becoming a common repair and strengthening technique for concrete structures. In this method continuous fibre sheets are bonded to the surface of a concrete structure using organic resins. The main disadvantages of this method are: (i) the use of resins (organic compounds) which are hazardous for the manual worker, and (ii) the low permeability of this type of organic materials. These problems could be solved if a cement-based matrix is used instead of epoxy matrix. In the current development stage one of the limiting parameter in a cementitious carbon fibre composite is the bond between the fibres and the cementitious matrix. The main objective of the study presented in this paper was to improve the bond between the carbon fibres and the cementitious matrix. Two possible methods were studied: (i) the design of a complex binder based on Portland cement with polymer and silica fume additions and (ii) surface treatment of the carbon fibres prior to their casting in the cementitious composite.

Comparative evaluation method of polymer surface treatments applied on high performance concrete

An investigation on the protection characteristics of three different polymer surface treatments applied on concrete was carried out by means of a large number of tests. Two of the polymers used, i.e., silane and siloxane, are commercial products, while the third, a fluorinated polymer, is still being studied. These treatments were applied on high performance concretes (0.33 water/cement ratio) with two different curing times. Their protection efficiencies were evaluated by testing water absorption (by immersion and by capillarity) and evaporation, chlorides penetration and artificial ageing; two other tests were carried out to verify concrete surface colour changes caused by applied treatments and by external exposure. To evaluate the overall behaviour of each product, the results obtained were translated into a parametric scale and reported using comparative graphics.

Treatment of organic polymer surfaces by CF4 plasmas: Etching by fluorine atoms and influence of vacuum ultraviolet radiation

Previous works have shown that atomic fluorine is the main etching agent of organic polymer surfaces subjected to fluorinated plasma treatments. In this work the etching probability per F atom impinging on a polymer-like material (hexatriacontane C36H74, a model molecule for high density polyethylene) has been estimated from direct measurements of the etching rate using a quartz crystal microbalance and from the absolute F atom concentration using threshold mass spectrometry. This etching probability has roughly the same value as the sticking probability of F atoms on this surface, which is in the range of 1%–3%. It has been pointed out that the reactivity of the surface with respect to F atoms is enhanced when the polymer surface is seen by the plasma. This could be due to either ions or vacuum ultraviolet (VUV) radiation. To more fully understand this point, we have built an external independent VUV source to irradiate the sample and we have used threshold ionization mass spectrometry to monitor the F atoms kinetics. The simultaneous irradiation of the substrate by VUV increases by a factor of 2 the reactivity of the substrate with respect to F atoms.

Ability of a gridless ion source to functionalize polypropylene surfaces by low-energy (60–100 eV) nitrogen ion bombardment. Effects of ageing in air and in water

Polymer surface treatments are of great importance for various industrial applications that can range from food packaging or car bumper painting to biocompatible implants. For such applications, plasma or corona discharges are well known and used “on-line” in polymer plants to incorporate new chemical functions at polymer surfaces. The aim of this work is to investigate the ability of a simple ion source to functionalize polypropylene surfaces in comparison with these intensively used industrial methods. Estimation of the influence of the nitrogen ion dose (from 1×10 15 to 1×10 16 ions/ cm 2 ) and the ion energy (from 60 to 100 eV) on incorporation is attempted in order to be able to use them in a controlled way. The ageing of these polymer surfaces in air and in water was studied by XPS for several months.

Atmospheric pressure plasma processing with microstructure electrodes and microplanar reactors

Atmospheric pressure plasmas can be generated, if the distance between the plasma generating electrodes is in the range of 100 μm, and radio-frequencies of 13.56 or 27.12 MHz are applied. Such small dimensioned plasmas are only of interest for industrial plasma applications if larger areas can be processed. It will be shown that both with microstructure electrodes as with microplanar-reactor, plasma processing can be carried out for typical substrate dimensions of 100 mm and more using helium or neon for plasma generation. First experiments of plasma surface treatment of polymers and of thin film deposition on silicon will be presented. With mixtures of some percentage C 2H 2 in atmospheric pressure helium, diamond-like carbon films with deposition rates between 1–10 μm/min can be deposited.

On plasma processing of polymers and the stability of the surface properties for enhanced adhesion to metals

This paper deals with the plasma surface treatment of polymers in a low frequency bell jar reactor with non-symmetrical configuration of electrodes. The highly energetic character of this discharge due to its low excitation frequency and electrode configuration, as well as its small discharge volume makes it a very efficient and fast functionalization process. Amongst the different plasma gases used for the adhesion improvement of polypropylene to aluminum, ammonia has shown to be the most suitable one for this application. Since the NH and NH 2 radicals play an important role in the kinetics of nitrogen incorporation in polymers, mixtures of N 2 and H 2 were also used as possible substitutes for ammonia. The former are more environmentally friendly and easier to handle in industry than ammonia. The efficiency of nitrogen rich mixtures in the case of the second application, i.e. adhesion improvement of copper to fluoropolymers has been compared to that of ammonia which still shows faster nitrogen incorporation. The last part of this paper is devoted to the study of the energetic character of plasmas of mixtures of He+NH 3 by OES and electrical measurements in the whole range of composition of the two gases. The results show that an ammonia percentage ranging from 5 to 10% in plasmas of mixtures of He/NH 3 represents a transition between two different discharge regimes. Plasmas of mixtures of He+2% NH 3, characterized by highly energetic electrons, ions and probably metastables of helium give rise to enhanced adhesion of PP to aluminum which remains stable with time.

Atmospheric pressure DC glow discharge for polymer surface treatment

We present a new approach for the surface treatment of polymer films at atmospheric pressure. The DC glow discharge is generated by applying a high voltage between two electrodes which are placed in a channel with a high flux of air. The air flow removes charge carriers from the plasma zone which prevents the formation of sparks. In the almost homogeneous plasma a comparably high electrical power is converted forming a high concentration of active species. The flowing air transports them to the polymer surface. We report the results of the first experiments with this set-up. The influence of various process parameters on the discharge properties is shown. The resulting alterations in the surface structure of the polymers are characterised by XPS and contact angle geometry.

A new approach to characterize crystallinity by observing the mobility of plasma treated polymer surfaces

We describe in this paper a novel method to characterize crystallinity by observing the difference in chain mobility of oxygen plasma treated polymer surfaces, and further compare the crystallinity with the values obtained by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). We modified polymer surfaces with an inductively coupled plasma system to introduce polar functional groups. The immobility parameters of plasma modified surfaces were obtained by measuring contact angles as a function of storage time in air. Due to highly restricted chain mobility in the crystalline region, the crystallinity can be estimated by the fraction of immobile polar groups remaining after chain reorientation.

Effect of surface treatment on polypropylene film-oil interactions

The results are being presented of an investigation to explore the possibility of using surface modification of biaxially oriented polypropylene (BOPP) film in the control of some polymer-oil interactions. The deposition of thin-film polymer structures by means plasma polymerization of styrene in r.f. glow discharges have been used as a method of polymer surface treatment. The change of some characteristics of polypropylene after treatment and effect of use of plasma polymer coating on polymer-oil interaction as well as on resulting dielectric properties of polymer-oil system have been investigated.

An In Situ Comparison between VUV Photon and Ion Energy Fluxes to Polymer Surfaces Immersed in an RF Plasma

Absolutely calibrated vacuum ultraviolet (VUV) spectroscopy has been used to determine the energy fluxes of VUV photons at an electrically floating substrate in a low-pressure 13.56-MHz radiofrequency plasma reactor used for polymer surface treatments. These fluxes have been compared with the positive ion flux that was reported in an earlier study. At the typical operating parameters of 10-mTorr pressure and 10-W power, the total VUV energy flux is 2.2 mW cm-2, compared with a value of 3.3 mW cm-2 from the ions. With increasing power (from 0.5 to 12 W), both the ion and VUV energy fluxes increase monotonically. However, as the pressure increases, (1−100 mTorr), the ion energy flux declines, while the VUV component increases. At discharge powers of 10 W, and pressures greater than 25 mTorr, the greater part of the energy flux to the surface is from the VUV photons. These measurements are used to determine which of the plasma components, VUV or ions, will be most effective in the treatment of polystyrene surfaces in a pure Ar plasma. Because of the low VUV absorption coefficient of polystyrene most of the photon flux penetrates through the outermost 2 nm of the polymer surface without attenuation. Consequently, we calculate that under typical plasma operating parameters, the ions play the major role in the modification of polystyrene surfaces because of their shorter stopping distances.

Surface modification of PTFE by plasma treatment

Plasma treatment of polymer surfaces is a well established method for improving surface properties. In this paper, the surface structure and adhesive bonding properties of PTFE treated by three types of plasma are reported. The results indicate that different plasma gases have different effects on the surface structure. Argon plasma treatment produced a highly cross-linked honeycomblike structure, while air and oxygen plasma treatment resulted in a surface displaying high aspect ratio protrusions. All experimental plasma treatments caused a marked improvement in overlap shear strength, with the highest shear strength achieved after oxygen plasma treatment. It was found that the overlap shear strength was also influenced by plasma power and plasma treatment time although excessive plasma treatment caused damage to the surface layer leading to decreased shear strength. The change in surface properties and roughened microstructure together contributed to the improvement in shear strength.

Ultrathin DLC and SiOx layer deposition on poly(ethylene terephthalate) and restriction of surface dynamics

The hydrophilicity of oxygen plasma-reated polymer surfaces decays with storing time in air environments. Because they are dense, highly crosslinked, and chemically stable, diamond-like carbon (DLC) films and silicon oxide films (SiO x ) were deposited on poly(ethylene terephthalate) by plasma-enhanced chemical vapor deposition to restrict polymer surface dynamics. In this study, the effects of ultrathin films on surface dynamics of these polymers were investigated. The layers were deposited on substrates with thickness below 100 A. The thickness of films was measured with a scanning analyzer ellipsometer, while ATR-IR spectroscopy and Raman spectroscopy were performed to observe the chemical structure of the films. Films below 50 A were also shown to be effective in stabilizing the plasma treated polymer surfaces.

Modification of polyimide in barrier discharge air-plasmas : Chemical and morphological effects

Chemical and physical modifications of polyimide (PI) surfaces caused by an air plasma have been studied. The plasma-induced surface changes of PI were investigated by using a local dielectric barrier discharge (DBD) in air at atmospheric pressure and room temperature as a function of the plasma exposure time and plasma power, while the excitation frequency was kept constant at about 130 kHz. The first results obtained in this work suggest that DBDs operating in air at atmospheric pressure can be an efficient alternative plasma source for surface treatment of polymers: a short time air plasma treatment of few seconds leads to chemical and physical changes including the rise of wettability, surface oxidation, and enhancement of surface roughness. Therefore, this simple kind of dry surface treatment seems to be an effective, low cost method for production of well-adhering subsequent layers such as metal films, paints, glues, etc. on DBD pretreated polymers.

Micromechanical characterisation of plasma treated polymer surfaces

It has been recently demonstrated that a physically thick (about 50 nm) interfacial region (‘interphase’) is formed between a plasma deposited film and the underlying plasma treated or untreated polymer substrate. This can have an important effect on the performance of optical coatings, protective coatings, barrier films for packaging, and others. In the present work we study the effect of N2 and He plasma treatment of polycarbonate on the surface and near-surface (composite) mechanical properties. Multi-technique mechanical testing (scratching and depth-sensing indentation) has been performed using a broad range of applied loads (1 mN–10 N). We demonstrate that low-load scratching provides a more surface-specific information on the hardness and scratch resistance than do other methods. We also point out the advantage of constant-load, multipass scratching compared to the progressive-load approach.

Improvement of the Switching Parameters of Addressable Bistable Type PDLC Displays with Dual Frequency Driven Liquid Crystal

AbstractImprovement of switching parameters is reported of bistable polymer dispersed liquid crystal (PDLC) with dual frequency driven liquid crystal in an acrylate polymer matrix. Low frequency voltage pulses result in the transparent state while high frequency pulses return to the opaque state; which is a time useful for practical applications, e.g. still pictures. Both states are maintained even when removing the applied voltage. Repeatedly applying of high frequency voltage pulses recover the device to the initial scattering state with high reproducibility. Polymer content and surface treatment of substrates drastically affect the PDLC droplet formation and also bistability as a result.

Investigating Radio Frequency Plasmas Used for the Modification of Polymer Surfaces

By use of Langmuir probes and energy-resolved mass spectrometry, the properties of a cold plasma suitable for the surface treatment of polymers are investigated. The 13.56 MHz radio frequency (rf) excitation is provided by an external coil, and we demonstrate that a plasma of Ar gas is capacitively coupled to the source coil. The spatial distributions of plasma and floating (self-bias) potentials, electron temperature Te, and plasma density ne have been investigated for a range of input powers (1−50 W) and gas pressures (10-3−10-1 Torr) using compensated Langmuir probes. Estimates of the rf potential amplitudes are also given. The energy distribution of plasma ions at plasma boundaries has also been measured, and the effect of the perturbation to the plasma parameters due to the presence of the polymer sample and the spectrometer has been quantified. A feature of these plasmas is the presence of large rf potentials (up to about 25Te) and high self-bias potentials (up to 80 V). We show that the presence of a mass spectrometer changes the plasma potential and alters the level of rf fluctuation in the plasma and thereby affects the ion energy distribution function at the sample surface. Estimates of ion and photon energy fluxes are made, and the relative importance of these two fluxes in terms of polymer modification at a pressure of 10-2 Torr is discussed.

低温プラズマ処理による輸液用プラスチック容器への薬剤吸着抑制効果

Plastics has been widely used at the hospitals and dominates the field of the manufacture of infusion bag sets and packaging materials as a disposable product. Recently, it has been reported, however, that expected drug effects could not be obtained owing mainly to the drug adsorption to the surface of plastic bags observed when several injection drugs such as nitroglycerin, isosorbide dinitrate, diazepam, and insulin were injected mixedly into a certain plastic intravenous bags. And there is a possibility of the occurrence of chemical reactions between the added drugs and the surface of plastic bags. We also can not deny the possibility of the dissolution of softener from the plastic bags. On the other hand, we have been working on the nature of plasma treatment of polymer surfaces by irradiation of low temperature plasma and its pharmaceutical application studies. In this study, we obtained the data concerning the effect of plasma treatment on the reduction of adsorption of insulin to the surface of ethylene-vinylacetate (EVA) bag.

Ion beam and plasma technology development for surface modification at Los Alamos National Laboratory

We are developing two high-throughput technologies for materials modification. The first is a repetitive intense ion beam source for materials modification through rapid surface melt and resolidification (up to 10 10 K s −1 cooling rates) and for ablative deposition of coatings. The short range of the ions (typically 0.1 to 10 μm) allows vaporization or melting at moderate beam energy density (typically 1–50 J cm −2). A new repetitive intense ion beam accelerator called CHAMP is under development at Los Alamos. The design beam parameters are: E = 200–250 keV, I = 15 kA, τ = 1 μs, and 1 Hz. This accelerator will enable applications such as film deposition, alloying and mixing, cleaning and polishing, corrosion and wear resistance, polymer surface treatments, and nanophase powder synthesis. The second technology is plasma source ion implantation (PSII) using plasmas generated from both gas phase (using radio frequency excitation) and solid phase (using a cathodic arc) sources. We have used PSII to directly implant ions for surface modification and as a method for generating graded interfaces to enhance the adhesion of surface coatings. Surfaces with areas of up to 16 m 2 and weighing more than a thousand kilograms have been treated in the Los Alamos PSII chamber. In addition, PSII in combination with cathodic source deposition has been used to form highly adherent, thick Er 2O 3 coatings on steel for reactive metal containment in casting. These coatings resist delamination under extreme mechanical and thermal stress.

Study of the surface properties and stability of polymer films treated by NH3 plasma and its mixtures.

This paper deals with the plasma surface treatment of polymers in a low frequency bell jar reactor with non-symmetrical configuration of electrodes. This special configuration of electrodes simulates the industrial surface treatment of polymers i.e. very short treatment times (milliseconds to a few seconds). The physicochemical properties of different polymers modified in such a reactor using ammonia and its mixtures have been investigated. The industrial aim of such treatments were for adhesion improvement in applications such as metallization and immobilization of proteins for the fabrication of immunosensors. The last part of this paper was devoted to the study of the stability of the plasma modified polymers which is an important issue for the industrial development of plasma processes. A pretreatment in a noble gas such as helium was proposed in order to stabilize the extreme surface layer via crosslinking before the functionalization treatment in ammonia plasma. In order to carry out the crosslinking and functionalization process in a one step process, mixtures of He+NH3 plasmas were studied.

Vacuum ultraviolet to visible emission of some pure gases and their mixtures used for plasma processing

The vacuum ultraviolet (VUV) to near infrared emissions (112⩽λ⩽880 nm) from molecular gases (H2 and O2) and molecular gas–noble gas mixtures (H2–Ar and O2–Ar) have been investigated with two separate spectrophotometric instruments. We report the influence of plasma parameters such as gas composition, pressure, and microwave power upon the plasma emission. In the case of mixtures with noble gases, we selected a range of plasma parameters so as to obtain very intense VUV emissions, which can be useful for the photochemical treatment of polymer surfaces. Some kinetics mechanisms involved are discussed.