The current work incorporates a microscopic study of the effect of fiber orientation on the fiber wetting process and flow of liquid droplets along filter fibers when subjected to airflow and gravity forces. Glass filter fibers in various combinations were oriented at various angles within a plane defined by the airflow direction and were supplied with distilled water in aerosol form. The behavior and flow of the liquid collected by the fibers were observed and measured using a specially developed microscope cell, detailed in the paper. The experimental results were compared to a theoretical model developed to describe the behavior. The theory and experimental results showed good agreement. The developed theory allows an optimum angle to be determined for the internal filter fiber structure in the design of wet filters. A sensitivity analysis of the model was conducted to determine the most important parameters. This will aid design of wet filtration systems such that maximal self-cleaning can be accomplished with minimal water use.

Modification of a selective area of a fluororesin surface was accomplished by using ArF excimer laser radiation and a boron complex with oleophilic or hydrophilic functional groups. The chemical stability of fluororesin is attributed to the presence of C-F bonds. The F atoms were abstracted by B atoms selectively from the area irradiated with excimer laser radiation and were replaced with the desired functional groups. In this modification, B(CH₃)₃ and B(OH)₃ were used: a boron compound with methyl groups to generate an oleophilic surface, and one with hydroxyl groups to generate a hydrophilic surface. As a result, the resin surface exposed to ArF laser radiation becomes oleophilic or hydrophilic. Both samples were bonded to stainless steel plates with an epoxy bonding agent and the tensile shear strength was 1.2 x 10⁷ Pa in both cases.

Polypropylene (PP) surface in water was photochemically modified to render it hydrophilic using ArF excimer laser radiation. The chemical stability of PP is attributed to the CH and CH₃ bonds present. Thus, it is considered that H atoms are selectively pulled out from the area irradiated with ArF excimer laser light and are replaced with OH functional groups in the presence of water. In this treatment, the irradiated sample becomes hydrophilic with enhanced adhesion properties. The experimental conditions for this surface treatment were ArF laser fluence of 12.5 mJ/cm² and a shot number of 10000. The treated PP and stainless steel were bonded with epoxy adhesive and the tensile shear strength was 46 kg/cm².

We examined the possibility of the surface modification of hydrophobic polystyrene (PS) and poly(methyl methacrylate) (PMMA) by ozone aeration, UV irradiation and combination of ozone aeration and UV irradiation (ozone/UV) in distilled water. The surface states of treated films and particles were investigated by means of contact angle, atomic force microscopy (AFM) and FT-IR measurements. According to the contact angle measurements, the values of the contact angle of ultrapure water on treated PS films decreased with an increase in the elapsed time of the treatments. The most remarkable decrease was seen in ozone/UV treatment. On the other hand, the contact angle on treated PMMA films slightly increased to an equal extent after three types of treatments. The film and the particle surfaces of PS with aromatic rings were found to be well modified with hydroxyl (OH) and carbonyl (CO) groups and to give the most remarkable effects in ozone/UV treatments, whereas those of PMMA with no aromatic ring were hardly modified, merely resulting in a slight disorder in their surface roughness. The experimental results on surface modification of PS and PMMA revealed that the ozone/UV treatment in distilled water is usable as one of the useful techniques for the surface modification of polymers with aromatic rings.

In this work we studied the effect of surface treatment of PET films, which are widely used in food packaging, on the adhesion value of ink layers based on polyvinyl chloride. To give high barrier properties to packaging laminates, the films used in their structure are coated with a nanolayer of aluminum oxide (AlOx). However, these films have a disadvantage associated with the low adhesion of adhesive and ink layers to the AlOx nanolayer. To eliminate this disadvantage, aluminium oxide nanolayer is additionally coated with various polymer coatings. In this work we studied the effect of a polyacrylic coating applied on top of an AlOx layer on improving the adhesion of ink layers. For PET films used in food packaging, optical and surface properties are also important. In this regard, additionally we measured surface free energy, coefficient of friction, and optical properties of the studied PET films. We also highlight the relationship of contact angles of wetting and the work of adhesion for the printing ink with the measured adhesion of ink layers.

We have explored the possibility of acquiring information on the molecular nature of some novel polymer films by following Zisman's approach of determining the critical surface tension γ_C which is considered to reflect the molecular composition of the solid surface. This led us to obtain equilibrium contact angle data, using both a series of pure liquids and various alcohol solutions, not only with the polymer films but also with solid surfaces of polystyrene and polymethylmethacrylate.

Lower values of γ_C were obtained with the solutions than with the pure liquids; these lower values are attributed to the preferential adsorption of the alcohol molecules at both the polymer-liquid and the polymer-vapour interfaces. The value of γ_C depends on the alcohol used, and is relatively independent of the solid : it is inferred that the alcohol is adsorbed with the hydroxyl group towards the polymer surface.

It is concluded that in certain cases, the value of γ_C obtained using solutions cannot be used as being characteristic of the solid (as has been suggested by Zisman), and that changes at the solid-vapour interface cannot be neglected when interpreting contact angle data. Several sets of data reported in the literature are discussed from this viewpoint. The Gibbs adsorption isotherms is applied to the contact angle data and the results add further weight to the conclusions regarding the occurrence of adsorption at both interfaces.

Despite the recognition of several sources of variation of contact angle, both between and within sessile drops on plane substrates, no comment has ever been made on the statistical treatment of observed angles, especially those around single drops. Circumperipheral observations are suggested as essential, and analysis using cos theta in an autocorrelation model is proposed as a general means of handling such data.

The optimization of heat-sealing process parameters, including time, temperature, and pressure, was performed on a monolayer linear low-density polyethylene (LLDPE) film. The seal properties examined for each process condition were: seal initiation temperature (T_si), plateau initiation temperature (T_pi), final plateau temperature (T_pf), plateau seal strength (SS_p), and failure mode. Increasing dwell time enhanced seal strength. However, it was found that the rate of this enhancement is different for each interval of dwell time. A narrow temperature plateau was observed for dwell times lower than 0.4 s and higher than 2 s, while in between a broad temperature window was observed. The pressure shows its influence up to the stage of wetting. And after providing the intimate contact between two film layers, additional increase in pressure does not enhance seal strength significantly. A 3D mapping of process safety zone was introduced for seal strength in the range of heat seal process variables for the very first time. The analysis of this 3D representation revealed that seal strength has a linear correlation with the square root of dwell time. In addition, the interfacial bond strength was shown to be proportional to the fraction of melted crystals. It was found that this fraction is determined by dwell time and temperature. Topography and morphology of surfaces after peeling revealed enlargement of fibrillar morphology to taller failure fracture complex shapes. Extensive roughness analysis on film surfaces after peeling found the much rougher surfaces after breakage of strong bonding.

Polypropylene (PP) film was treated with radio-frequency-induced oxygen plasma, followed by the vacuum deposition of aluminum (Al) thin film, and the peel strength of the Al deposited PP film (Al/PP) was examined. The peel strength of plasma-treated PP film varied widely in the range of 6.7 to 157 N/m depending upon the plasma treatment conditions, whereas that of the untreated PP was 5.2 N/m. The peel strength was minimized at oxygen pressure near 13.3 Pa (0.1 Torr), and decreased with increasing discharge power. The peel strength rapidly increased at the initial stage of plasma treatment (∼ several seconds), decreased at the second stage, and slightly increased again at the third stage. A good agreement was found between the peel strength of Al/PP and the amounts of oxygen introduced onto the PP surface at the initial stage. A short-time treatment was very effective to improve the adhesion of Al/PP. At the end of the second stage, a large amount of carbon was detected by XPS on the Al layer of the peeled interface of Al/PP, which gave a minimum peel strength. Cohesive failure of PP film might have occurred. SEM photograph showed that PP surface was etched by oxygen plasma at the thrid stage. These peel behaviors of Al/PP were explained by the chemical and physical changes of the PP surface caused by oxygen plasma treatment: (1) introduction of O-functional groups onto the PP surface at the initial stage, (2) formation of weak booundary layers resulting from the partial scission of PP molecules at the second stage, and (3) plasma etching of the PP surface at the third stage.

Surface structures of poly(ethylene terephthalate) films produced by stretching after Ar plasma-treatment were analyzed by X-ray photoelectron spectroscopy, combined with a gas chemical modification technique, secondary ion mass spectrometry, and transmission electron microscopy. The formation of ultra-fine protrusions that produce good slip and a smooth film surface after the stretching procedure was confirmed. The height of the protrusions was almost the same as the thickness of the osmic acid-dyeable layer. The thickness of the modified layer was found to change according to the Ar pressure of the plasmatreatment. Carboxylic and hydroxyl groups produced by the plasma-treatment were quantified. The formation of these functional groups can explain good adhesion of the film.

Gas phase chemical modification (GCM) is found to be more preferable as a pretreatment for the XPS surface analysis of polymer materials than the conventional liquid phase treatment because it can circumvent problems such as solvent contamination and swelling. We have tried the quantification of the surface composition successfully by estimating the yield of the reaction from model samples. GCM was then applied to correlate the surface composition of NH₃ plasma-treated polystyrene films with their cell-affinity. The amount of primary-amine and that of carboxylic acid were directly determined by GCM. Although the amount of primary-amine, 15–20% of total nitrogen, did not depend on the treatment intensity, the total amine content for the treated samples increased with the plasma treatment intensity. The quantity of carboxylic acid generated was found to be very small. All treated samples had better cell-affinity than the control. The sample N2 (of medium treatment) showed the best cell-affinity. The most strongly treated sample N3, with larger amine content than N2, showed worse cell-affinity because of the interference by the sputtered SiO₂ on the surface.

The effects of 1, 2, 3, 4-tetrahydronaphthalene (tetralin) solvent and ammonia plasma treatments on surface characteristics and adhesion of ultra-high-strength polyethylene (UHSPE) fiнbers to epoxy resin were studied. Spectra™ 1000 (UHSPE) fibers were treated with either tetralin solvent or in combination with ammonia plasma, under various conditions. The changes in the fiber surface topography were characterized using scanning electron microscopy (SEM). Dynamic wetнtability measurements were made using the Wilhelmy technique. The fiber/epoxy resin interfacial shear strength (IFSS) was evaluated by the single fiber pull-out test. The fiber surfaces after the pull-out test were characterized by SEM. The SEM photomicrographs and wettability data showed that the surface roughness of the fibers increased after the tetralin solvent treatment and the fiber surface became more polar after the ammonia plasma treatment. The IFSS results indicated that combined tetralin and ammonia plasma treatments resulted in significant improvement in the adheнsion strength of UHSPE fibers with epoxy resin. This is attributed to the chemical, mechanical and topographical changes of the fibers resulting from the treatments.

Recently, much attention has been paid to gas discharges producing nonthermal plasma because of many potential benefits in industrial applications. Historically, past work focused on Dielectric Barrier (silent) Discharges (DBD) and pulse-periodical corona discharges. Recently, a number of new different discharge techniques succeeded in producing stable gas discharge at atmospheric pressure. Among these are repetitively pulsed glow discharge; continuous glow discharge in a gas flow; hollow-cathode atmospheric pressure discharge; RF and microwave (MW) discharges. Several new variants of the DBD have been demonstrated over a rather wide range of frequencies. All these forms of gas discharge are characterized by a strong nonequilibrium plasma state. We attempt to classify these discharges with respect to their properties, and an overview of possible applications is made. Conditions for the existence of homogenous and filamentary forms of each of the discharge types are discussed.

Polyolefins are well-known and the most commonly used polymers worldwide. Advantages like outstanding mechanical properties, chemical resistance, low cost, and processability are neighboring with some drawbacks like relatively high gas and vapor permeability, low surface energy. This chapter introduces surface plasma modification as an environmentally friendly, fast, and versatile technique. Details regarding different plasma reactor designs, generation methods, working parameters suitable for treating polyolefins are presented. Furthermore, plasma activation, grafting, and etching are described as the most commonly used techniques for surface energy modification to enhance polyolefins' biocompatibility, printability, adhesion to materials, and other parameters. For instance, plasma activation cross-linking of the polymer chains can be achieved, which leads to gas and vapor permeability improvement. Choice of working conditions allows controlling the degree of cross-linking, the type, and the concentration of the incorporated functional groups on the surface. Plasma polymerization is introduced as a technique for coating deposition with different properties and functionality depending on the operating parameters and monomer selection. Improvement of barrier layer performance and modification of the surface energy are the main applications of plasma polymerization of polyolefins.

The peel characteristics of sealed low-density polyethylene/isotactic polybutene-1 (PE-LD/iPB-1) films, with different contents of iPB-1 up to 20 m.-% (mass percentage), were evaluated and simulated in dependence on the iPB-1 content, and in dependence on the peel rate. Sealing involves close contact and localized melting of two films for a few seconds. The required force, to separate the local adhered films, is the peel force, which is influenced, among others, by the content of iPB-1. The peel force decreases exponentially with increasing iPB-1 content. Transmission electron microscopy studies reveal a favorable dispersion of the iPB-1 particles within the seal area, for iPB-1 concentrations ≥6 m.-%. Here, the iPB-1 particles form continuous belt-like structures, which lead to a stable and reproducible peel process. The investigation of the peel rate-dependency on the peel characteristics is of important interest for practical applications. The peel force increases with increasing peel rate by an exponential law. A numerical simulation of the present material system proves to be useful to comprehend the peel process, and to understand the peel behavior in further detail. Peel tests of different peel samples were simulated, using a two-dimensional finite element model, including cohesive zone elements. The established finite element model of the peel process was used to simulate the influence of the modulus of elasticity on the peel behavior. The peel force is independent of the modulus of elasticity, however, the peel initiation value increases with increasing modulus of elasticity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 https://onlinelibrary.wiley.com/doi/10.1002/app.28999

The interaction between a low-pressure gas plasma and organic materials has mechanical (surface cleaning and dry micro-etching) and electrostatic (cross-linking and surface activation) effects. Corrosion of a fluorinated ethylenepropylene (FEP) sample was studied for different conditions. The corrosion rate of FEP depends on the gas and on the gas pressure and has the highest value for oxygen. The modifications of the sample surface were studied by contact-angle measurements for water and formamide and by the thermally stimulated discharge current method. The optimum parameters for a continuum vacuum metallization process of FEP are presented.

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.

Ultra-high strength polyethylene fibers were treated with excimer laser and high power ion beams (HPIB) to enhance their adhesion to epoxy resins. Laser treatments were carried out in air, argon, and helium environments and HPIB treatments were carried in vacuum. The effects of these treatments on the surface topography and chemistry were characterized using several techniques. It can be seen from the results that both laser and HPIB treatments increased the fiber surface roughness as well as the surface polarity. HPIB treated fibers had a characteristic bumpy surface while the laser treated fibers had deeper striations or a rougher surface. Although the total surface energy did not change after the treatments, the acid-base component increased significantly and the dispersive component decreased by almost the same amount. After the treatments the fiber-epoxy interfacial shear strength (IFSS) increased between 200 to 300%. This enhancement is attributed to the increased roughness of the fiber surface and increased specific interface area, increased polar nature and wettability, as well as improvement in the acid-base component of the surface energy.

An equation of state is developed which allows the surface tension of a low-energy solid to be determined from a single contact angle formed by a liquid which is chemically inert with respect to the solid and whose liquid surface tension is known. The equation of state is obtained using two independent methods. In the first one, similar arguments to those in previous papers are used; however, the qualitative argument, based on the general appearance of plots, is replaced by computer curve fitting and statistical analysis. The second method, which has not been employed heretofore, treats the solid surface tension as an adjustable parameter. Molecular arguments in conjunction with the interaction parameter Φ are used to eliminate poor choices of the solid surface tension. The results are in excellent agreement with the first method.

The range of validity of the equation of state and practical points in its application are discussed.

A technique is described for performing temperature scanning measurements of the surface tension of polymer solutions. Measurements on solutions of a high molecular weight and a low molecular weight monodisperse polystyrene in tetralin, decalin, and n-hexadecane are reported. Whereas previous investigations of other physical properties of polystyrene solutions had revealed only one anomaly, at about 50°C in some cases and at about 70–80°C in others, the curves presented here show two anomalies, near 45°C and 70°C, respectively. These anomalies are tentatively attributed to conformational changes of the polymer chains.