Water Drop Contact Angle Measurements Research Articles

An effective material for solar steam generation applications: Gradient graphene sponge

The efficient use of solar energy for clean water is a renewable and environmentally-friendly route to solve global water scarcity. For this, we report the preparation of light, mechanically durable, and effective photothermal material. A simple acid impregnation method was applied to graphene sponge material (GSM) possessing hydrophobic character to gain partial hydrophilicity to obtain a gradient structure. The morphological and structural properties of the gradient graphene sponge material (GGSM) were carried out using scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray powder diffraction patterns, Fourier-transformed infrared spectroscopy, and water drop contact angle measurements. GGSM showed fast and effective water vapor conversion performance due to the gradient structure, as well as the high rate of sunlight absorption and photothermal conversion thanks to graphene. With the advantageous feature of gradient structure, GGSM achieved a high water vapor conversion capacity (1.79 kg/m2h) and solar thermal efficiency of 57% compared to GSM (1.58 kg/m2h; 45%). This new material provides a novel approach to solar energy applications.

Functionalization of Plasma Electrolytic Oxidation/Sol–Gel Coatings on AZ31 with Organic Corrosion Inhibitors

In this investigation, the sol–gel method is employed along with a corrosion inhibitor to seal a plasma electrolytic oxidation (PEO) coating, aiming to improve the long-term corrosion resistance of the AZ31 Mg alloy. Following an initial screening of corrosion inhibitors, 8-hydroxyquinoline (8HQ) is incorporated into the hybrid PEO/sol–gel system using two methods: (i) post-treatment of the PEO layer through immersion in an inhibitor-containing solution; (ii) loading the inhibitor into the sol–gel precursor. The characterization includes scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), and water drop contact angle measurements. The rheological properties of the inhibitor-loaded sol–gel precursors are assessed by measuring flow curves. The corrosion processes are evaluated in a saline solution through electrochemical impedance spectroscopy (EIS) and immersion tests with unscratched and scratched specimens, respectively. The results demonstrate the successful incorporation of the inhibitor for both loading strategies. Regardless of the loading approach, systems containing 8HQ exhibit the most favourable long-term corrosion resistance.

Surface modifications of a silicalite film designed for coating orthopaedic implants

The effect of various surface modifications of silicalite-1 film grown on a Ti6Al4V alloy on biocompatibility and cell differentiation has been addressed. The as-synthesized silicalite film was first modified by alkaline etching and by subsequent treatments in oxygen radiofrequency (O2 RF)plasma, by calcination at 500 °C, and by processing the calcinated samples in the O2 RFplasma. The chemical composition, crystallinity, topography and wettability of samples were characterized using angle-resolved X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and sessile water drop contact angle measurements. We have discovered the presence of a non-zeolitic defective SiOx phase (NZP) with coordinated hydrocarbon chains. The NZP can be removed by the exposition to the O2 RF plasma. The metabolic activity tests done on human osteoblast line Saos-2 revealed that the NZP can influence cell proliferation; however, all studied modifications of silicalite film can be considered biocompatible. The osteogenic differentiation was studied on human mesenchymal stem cells under static conditions and under dynamic (pulsatile and shear) stress. The results obtained by the real-time qPCR and immunofluorescence microscopy suggest that etched, plasma-treated and calcinated + plasma-treated samples are the most promising for osteogenic cell differentiation.

Smanjenje sposobnosti upijanja vode papira oslojenih filmovima na bazi nanofibrilisane celuloze

Nanofibrillated films based on TEMPO-oxidized cotton linters were applied to reduce the hydrophilic properties of paper. For this purpose, aqueous dispersions of nanofibrillated cellulose of different composition: 1 and 3% of nanofibrillated cellulose, up to 13% of CaCO3 and/or Al(OH)3, up to 20% of propane-1,2-diol (glycol), and up to 21% of TEMPO-oxidized cotton linters were coated on the model paper, without additional adhesive. The pristine model paper and papers coated with nanofibrillated cellulose-based composite films were characterized in terms of water absorptiveness by COBB method and water drop contact angle measurements. The surface appearance was characterized by scanning electron microscopy (SEM) and surface chemistry by infrared spectroscopy with Fourier transform and attenuated total reflection (ATR-FTIR). Additionally, optical properties, i.e. measurement of reflection curves and CIE degrees of whiteness, were determined according to appropriate standards. For all papers coated with nanofibrillated cellulose-based films, depending on the composition of the dispersions, a decrease in sorption properties was achieved, without changes in optical properties and surface morphology of the paper compared to the pristine paper.

Plasma modification of heparinised CNT/PU nanocomposite and measuring of mechanical, calcification and platelet adhesion properties for application in heart valve

ABSTRACT In this study, the calcification and platelet adhesion resistance property of plasma-treated polyurethane/heparinised carbon nano tube (PU/HCNT) nanocomposite thin films as a candidate polymer for polymeric heart valve was investigated. The PU and HCNTs nanocomposite films (PU/HCNT) were prepared using the solvent casting technique. CNTs were heparinised to surpass the dispersal and calcification resistance of CNTs in the PU matrix. Dispersal of CNTs in the matrix of produced films was analysed with (TEM), and HCNTs were observed well distributed in the polymer matrix. Greater storage modulus and better calcification resistance were detected for the nanocomposite. DMTA used for determining nanocomposite properties, which showed that the modulus increased as modified CNTs added to the matrix. The composite films were exposed to oxygen plasma treatment. The modified surface was characterised using ATR-FTIR, SEM, EDXA, and water drop contact angle measurements. The results indicated that the treated PU/HCNT surface was more hydrophilic. Increased surface roughness for modified PU/HCNT surface observed in AFM images. In-vitro calcification test verified reduced calcification for the modified PU/HCNT surface. No cytotoxicity was observed for the modified polymeric films using L929 fibroblast cells. The platelet adhesion test showed that the modified films are more blood compatible than unmodified.

Are Metal Complexes “Organic,” “Inorganic,” “Organometallic,” or “Metal-Organic” Materials? A case Study for the Use of Trinuclear Coinage Metal Complexes as “Metal-Organic Coatings” for Corrosion Suppression on Aluminum Substrates

This article provides a second manifestation of a new tradition by which the editors of Comments on Inorganic Chemistry wish to lead by example, whereby we start publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for “critical discussion of the current literature” of inorganic chemistry. (For the first manifestation, see: Otten, B. M.; Melancon, K. M.; Omary, M. A. “All That Glitters is Not Gold: A Computational Study of Covalent vs Metallophilic Bonding in Bimetallic Complexes of d10 Metal Centers—A Tribute to Al Cotton on the 10th Anniversary of His Passing,” Comments Inorg. Chem. 2018, 38, 1–35.) Thus, herein we show that a trinuclear copper (I) complex {[3,5-(CF3)2Pz]Cu}3 (henceforth referred to as the “Cu trimer”) can act as a “metal-organic coating” for corrosion protection of aluminum, whereas its silver analogue, {[3,5-(CF3)2Pz]Ag}3 (i.e., the “Ag trimer”), could not. The manuscript was initially submitted to journals that usually publish on “organic coatings” but was rejected on the premise that a metal complex cannot be considered “organic” unless it is incorporated into a polymer. This issue is commented upon herein in the broader context of whether to consider metal complexes “organic,” “inorganic,” “organometallic,” or “metal-organic” materials with manifestations of the use of each classification in the literature. We have found that, upon coating the Cu trimer onto an aluminum (AA 3003) surface, potentiodynamic polarization results in 3.5% NaCl show an increase in corrosion potential (Ecorr) by ~ 0.6 V concomitant with a three-order-of-magnitude decrease in corrosion current density (icorr) from 0.025 µA/cm2 for uncoated aluminum to ~ 9.6 × 10–5 µA/cm2 for the Cu trimer-coated surface. With a double coating, the Cu trimer formed a completely insulating surface with no current flow, even at very high potential magnitude and range. Open circuit potential was used to study the stability of the Cu trimer films on the Al surface in the electrolyte solution. Scanning electron microscopy and Fourier-transform infrared spectroscopy techniques were used to characterize the structure of both the Cu trimer powder and Cu trimer film on the aluminum surface before and after the corrosion tests. The hydrophobicity of the Cu trimer coating was determined by using water drop contact angle measurements, which demonstrated an increase from 65° to 137° for the uncoated and coated aluminum, respectively. The thermal stability of the Cu trimer was analyzed using thermogravimetric analysis, giving rise to weight loss resistance up to ~190 °C. The results clearly demonstrate that the Cu trimer layers exhibit superior stability and potential for corrosion protection of aluminum surfaces in corrosive environments. The Ag trimer analogue, meanwhile, failed the “tape test” that the Cu trimer passed to assess the mechanical stability of such “metal-organic” coatings. Density functional theory (DFT) simulations provide insights on this difference upon modeling the interaction of each cyclotrimer molecule (and other analogous ones) with an Al atom on the one hand and contrasting the resulting binding energies with the corresponding dissociation energies of the metallophically-bound crystalline solid form of each trimer. Thus, it was found that Ag trimer models are bound to the Al atom at least as strongly as Cu trimer models are; yet, that bonding is not sufficiently high so as to overcome the argentophilic attraction, whereas it can overcome the cuprophilic attraction. Other explanations are also given to account for trimer interactions with aluminum oxide as well as partial oxidation of only the Cu trimer, which strengthens the interaction with the Al atom.

Vapor-Phase Plotting of Organosilane Chemical Gradients.

Vapor-phase plotting of organosilane-based self-assembled monolayer (SAM) gradients is demonstrated for the first time. Patterned SAMs are formed by delivering gas-phase organotrichlorosilane precursors to a reactive silica surface using a heated glass capillary. The capillary is attached via a short flexible tube to a reservoir containing the precursor dissolved in toluene. The proximal end of the capillary is positioned at an experimentally optimized distance of 30 μm above the substrate during film deposition. The capillary is mounted to a stepper-motor-driven X, Y plotter for raster scanning above the surface. Two different organotrichlorosilane precursors are employed in this initial demonstration: n-octyltrichlorosilane and 3-cyanopropyltrichlorosilane. The dependence of SAM deposition on ambient relative humidity, capillary-substrate separation, raster-scanning speed, and solvent viscosity and volatility is explored and optimum deposition conditions are identified. The optimized procedures are used to plot uniformly modified square "pads" and gradients of the silanes. Film formation is verified and the gradient profiles are obtained by sessile drop water contact angle measurements, spectroscopic ellipsometry measurements of film thickness, and X-ray photoelectron spectroscopy mapping. The resolution of the plotting process is currently in the millimeter range and depends on capillary diameter and distance from the substrate surface. Vapor-phase plotting affords a unique direct-write method for producing patterned and chemically graded SAMS that may find applications in microfluidic devices, planar chromatography, and optical and electronic devices.

Single Molecule Catch and Release: Potential-Dependent Plasmid DNA Adsorption along Chemically Graded Electrode Surfaces.

Single molecule detection methods were employed to study the potential dependent adsorption and desorption of dye labeled plasmid DNA along chemical gradients prepared on indium tin oxide (ITO) electrodes. Gradients were formed over silica-base-layer-coated ITO surfaces by exposing them in a directional fashion to aminopropyltrimethoxysilane from the vapor phase. Sessile drop water contact angle measurements, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy were used to verify that a gradient was formed and to characterize its wettability, thickness, and composition as a function of position. The gradient-coated ITO electrode served as both the working electrode and a window into the electrochemical cell used to manipulate DNA adsorption. For single molecule studies, the electrochemical cell was filled with buffer solution containing YOYO-1-labeled plasmid DNA. Fluorescence videos acquired along the gradients depicted clear position-, potential-, and pH-dependent variations in DNA adsorption and desorption. The results demonstrate that DNA adsorption was largely independent of applied potential and irreversible at high amine coverage (i.e., multilayers), under pH ∼ 6 buffer. DNA adsorption became more reversible as the amine coverage decreased and the solution pH increased. Potential dependent control over DNA adsorption and desorption was best achieved at monolayer-to-submonolayer aminosilane coverage under pH ∼ 8 buffer. The knowledge gained in these studies will aid in the development of electrochemical methods for the capture and release of DNA and other polyelectrolytes at electrode surfaces.

Interaction of human osteoblast-like Saos-2 cells with stainless steel coated by silicalite-1 films

This paper investigates the interaction of human osteoblast-like Saos-2 cells with stainless steel covered by a film of densely inter-grown silicalite-1 crystals with defined outer and inner surfaces. The chemical composition of this film, labeled as SF(RT), was tuned by heat treatment at 300°C and 500°C (labeled as SF(300) and SF(500), respectively) and characterized by X-ray photoelectron spectroscopy (XPS), water drop contact angle (WCA) measurements and scanning electron microscopy (SEM). The number, the spreading area and the activity of alkaline phosphatase of human osteoblast-like Saos-2 cells in cultures on the silicalite-1 film were affected by the chemical composition of its outer surface and by its micro-porous structure. The number and the spreading area of the adhered osteoblast-like cells on day 1 was highest on the surface of SF(RT) relative to their adhesion and spreading on a glass cover slip due to the SF(RT) topology. However, SF(300) markedly supported cell growth during days 3 and 7 after seeding.

Fine Tuning Surface Energy of Poly(3-hexylthiophene) by Heteroatom Modification of the Alkyl Side Chains.

Recent work has pointed to polymer miscibility and surface energy as key figures of merit in the formation of organic alloys and synergistic behavior between components in ternary blend solar cells. Here, we present a simple model system and first report of poly(3-hexylthiophene)-based random copolymers featuring either a semifluoroalkyl (P3HT-co-FHT) or oligoether (P3HT-co-MET) side chain, prepared via Stille polycondensation. Water drop contact angle measurements demonstrated that P3HT-co-FHT polymers reached a minimum surface energy of 14.2 mN/m at 50% composition of comonomers, while in contrast, P3HT-co-MET polymers increased as high as 27.0 mN/m at 50% composition, compared to P3HT at 19.9 mN/m. Importantly, the surface energy of the copolymers was found to vary regularly with comonomer composition and exhibited fine-tuning. Optical and electronic properties of the polymers are found to be composition independent as determined by UV-vis and CV measurements; HOMO energy levels ranged from 5.25 to 5.30 eV; and optical band gaps all measured 1.9 eV. Following this model, surface energy modification of state-of-the-art polymers, without altering desirable electronic and optical properties, is proposed as a useful tool in identifying and exploiting more alloying polymer pairs for ternary blend solar cells.

Electrochemical Insights on the Hydrophobicity of Cellulose Substrates Imparted by Enzymatically Oxidized Gallates with Increasing Alkyl Chain Length.

In this work, we studied the influence of the alkyl chain length in enzymatically oxidized gallates on the development of hydrophobicity on paper-based materials, and further correlated the obtained effect to the redox mechanism of the enzymatic treatment. Laccase (Lac) enzyme was used to oxidize various members of the gallate homologous series in the presence or not of lignosulfonates (SL) to produce several functionalization solutions (FS), which were subsequently applied to cellulosic substrates. The hydrophobicity of the substrates was then assessed by means of water drop test (WDT) and contact angle (WCA) measurements. Hydrophobicity peaked reaching WDT and WCA values around 5000 s and 130°, respectively, and then decreased with increasing length of the hydrocarbon chain of gallate. Cyclic voltrammetry (CV) was used to study the effect of SL on the redox reactions of several gallates. The intensity of the anodic peak in their voltammograms decreased increasing the chain length of the gallate. The electrochemical behavior of lauryl gallate (LG) differed from that of other gallates. The fact that the voltammetric curves for SL and LG intersected at a potential of 478 mV indicates an enhancing effect of SL on LG oxidation at high potentials (above 478 mV).

The origin and reversible nature of poultry litter biochar hydrophobicity.

Transient changes in wettability complicate the prediction of biochar's hydrologic effects. Biochar wetting properties were characterized from poultry litter biochar (PLBC) produced from slow pyrolysis at temperatures between 300 and 600°C with water drop penetration time (persistence of hydrophobicity) and contact angle (CA; severity of hydrophobicity) measurements. Hydrophobicity was associated with semivolatile organic compounds coating PLBC surfaces, which resulted in 24.4 carbon layers and CAs of 101.1 ± 2.9° at a pyrolysis temperature of 300°C but only 0.4 layers of surface coverage and CAs of 20.6 ± 1.3° when pyrolyzed at 600°C. Mixing PLBC with water removed organic coatings, and storage in water for 72 h decreased CA as much as 81° for the most hydrophobic PLBCs. When mixed with quartz sand of the same particle size, CAs of PLBC-sand mixtures increased from 6.6 ± 1.4° at 0% PLBC mass fraction to 48.3 ± 2.0° at 15% mass fraction. Hydrophobic and hydrophilic PLBCs increased CA by nearly identical amounts at 2 and 5% mass fractions, which was explained by the influence of PLBC particle topology on macroscopic surface roughness of PLBC-sand mixtures. For environmentally relevant situations, PLBC-sand mixtures at mass fractions ≤15% remained water wetting. However, all PLBC additions increased CA, which may alter infiltration rates and induce preferential water flow.

Wet Chemical Functionalization of GaP(111)B through a Williamson Ether-Type Reaction

Functionalization of crystalline gallium phosphide (GaP) (111)B interfaces has been performed through the formation of P–O–R surface bonds. The approach described herein parallels classical Williamson ether synthesis, where hydroxyl groups on etched GaP(111)B surfaces were reacted with halogenated reactants. Grazing angle total internal reflectance infrared spectra showed increased intensities for −CH2– and −CH3 asymmetric and symmetric stretches after reaction with long alkyl halides. Changes in the X-ray photoelectron spectra collected before and after reaction separately corroborated surface attachment to GaP(111)B. Static sessile drop water contact angle measurements for GaP(111)B separately showed increased hydrophobicity following surface modification with long alkyl chains. The surface functionalization reaction rate was increased by the addition of non-nucleophilic bases, consistent with surface deprotonation as the rate-limiting step. Separately, photoelectrochemical measurements conducted before and after reaction with alkyl halides at long wavelengths (λ > 545 nm) showed surface attachment decreased sub-band-gap photocurrents, implying lowered activity of surface traps. Conversely, photoelectrochemical measurements performed after functionalization of p-GaP(111)B with Coomassie Blue sulfonyl chloride showed evidence of persistent sensitized hole injection from the dye into p-GaP.

Single-Molecule Spectroscopic Imaging Studies of Polarity Gradients Prepared by Infusion-Withdrawal Dip-Coating

Sol–gel-derived thin films incorporating a one-dimensional polarity gradient are prepared by infusion-withdrawal dip-coating (IWDC) and characterized by single-molecule spectroscopic (SMS) imaging. Nonpolar phenyltrimethoxysilane (PTMOS) and polar tetramethoxysilane (TMOS) are used as precursor silanes during IWDC. Sessile drop water contact angle measurements demonstrate the presence of a wettability gradient in the resulting films, on macroscopic length scales. Raman maps of the phenyl C–H stretch at 3059 cm–1 confirm gradient formation. Material polarity is assessed by SMS imaging, using Nile Red as a polarity-sensitive probe. Polarity data are obtained by recording fluorescence videos of single-molecule emission simultaneously in two spectral bands (590 ± 20 and 640 ± 20 nm). The pairs of fluorescence spots produced by each molecule are identified and analyzed using automated spot-tracking software. The local film polarity is quantified via the Clausius–Mossotti factors calculated from the single-mole...

Coating a polystyrene well-plate surface with synthetic hematite, goethite and aluminium hydroxide for cell mineral adhesion studies in a controlled environment

Iron and aluminium oxides are available in many climatic regions and play a vital role in many environmental processes, including the interactions of microorganisms in contaminated soils and groundwater with their ambient environment. Indigenous microorganisms in contaminated environments often have the ability to degrade or transform those contaminants, a concept that supports an in situ remediation approach and uses natural microbial populations in order to bio-remediate polluted sites. These metal oxides have a relatively high pH-dependent surface charge, which makes them good candidates for studying mineral–bacterial adhesion. Given the importance of understanding the reactions that occur at metal oxide and bacterial cell interfaces and to investigate this phenomenon further under well-characterized conditions, some of the most common iron and aluminium oxides; hematite, goethite and aluminium hydroxide, were synthesized and characterized and a coating method was developed to coat polystyrene well-plates as a surface exposable to bacterial adhesion with these minerals (non-treated polystyrene-12 well-plates which are used for cell cultures). The coating process was designed in a way that resembles naturally coated surfaces in aquifers. Hematite, Fe2O3, was synthesized from acidic FeCl3 solution, while goethite, FeOOH, and aluminium hydroxide, Al(OH)3, were prepared from an alkaline solution of Fe(NO3)3 and Al(NO3)3. They were further characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), potentiometric titration and contact angle measurements. Characterization results show that the pure phases of hematite, goethite and aluminium hydroxides are formed with a point of zero charge (PZC) of 7.5, 8.5 and 8.9, respectively. The coating process was based on the direct deposition of mineral particles from an aqueous suspension by evaporation. Then, altered polystyrene surface properties were analyzed using X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared (ATR-IR), water drop contact angle measurements and vertical scanning interferometry (VSI). The surface analysis tests prove that the coated polystyrene surface has physicochemical properties that are similar to the reference synthetic hematite, goethite and aluminium hydroxide minerals. These prepared and well-characterized mineral well-plates are similar to naturally occurring surfaces in aquifers and enable us to study the different steps of bacterial adhesion and biofilm formation on these metal oxides under laboratory-controlled conditions.

Surface Modification of Castor Oil‐Based Polyurethane by Polyacrylic Acid Graft using a Two‐Step Plasma Treatment for Biomedical Applications

ABSTRACTThe aim of this study is design and prepare medical grade polyurethane (PU) film based on castor oil without any additives. Acrylic acid (AAc) was grafted onto the surface of PU films using a two‐step oxygen plasma treatment. The first step of this method includes oxygen plasma pretreatment of the PU films, immersion in AAc monomeric solution, removal from the solution, and drying. The second step was carried out by plasma polymerization of preadsorbed reactive monomers on the surfaces of dried pretreated films. The effects of pretreatment time length and monomer concentration were studied on AAc graft amount. The surface of the modified PU films were characterized using attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy, scanning electron microscopy (SEM), and water drop contact angle measurements. The ATR‐FTIR results proved that the carbonyl (CO) and hydroxyl groups (OH) of AAc give rise to an absorption peak at 1698 cm–1, which was observed in the spectra of the modified PU. The SEM micrographs showed that poly(acrylic Acid) (PAAc)–grafted PU films have a different pattern compared with nonmodified PU films. Moreover, it was found that a decrease in contact angle indicated to a higher grafting amount of polymer. Finally, L929 fibroblast cell culture was done onto the PAAc–PU films. It was observed that cells are spherical and not uniformly distributed on the modified polymer surface.

Immobilization of [60]fullerene on silicon surfaces through a calix[8]arene layer

In this work, we report the functionalization of flat Si(100) surfaces with a calix[8]arene derivative through a thermal hydrosilylation process, followed by docking with [60]fullerene. Chemical grafting of calix[8]arene on silicon substrates was evaluated by X-ray photoelectron spectroscopy, whereas host-guest immobilization of fullerene was demonstrated by atomic force microscopy and sessile drop water contact angle measurements. Surface topographical variations, modelled on the basis of calix[8]arene and [60]fullerene geometrical parameters, are consistent with the observed morphological features relative to surface functionalization and to non-covalent immobilization of [60]fullerene.

Chitosan/heparin surface modified polyacrylic acid grafted polyurethane film by two step plasma treatment

The aim of this study is to design an artificial skin dress. A multilayer skin dressing included synthesised castor oil based polyurethane (PU) as the outer layer and two biopolymeric layers of heparin and chitosan as the inner layers were prepared. The surface of PU film was activated using two steps oxygen radio frequency plasma treatment. The surface of the modified PU films characterised by attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy and water drop contact angle measurements. Scanning electron microscopy observations confirmed the presence of grafted poly acrylic acid on the surface of PU films. Also, heparin and chitosan were immobilised on PU films. In vitro cell culture showed that the samples have an excellent biocompatibility with L929 fibroblast cells. Cell adhesion and proliferation of cells on the chitosan/heparin immobilised surfaces showed better behaviours compared with poly (acrylic acid) grafted PU film.

A comparison of reactive plasma pre-treatments on PET substrates by Cu and Ti pulsed-DC and HIPIMS discharges

PET web samples have been treated by magnetically enhanced glow discharges powered using either medium frequency pulse direct current (p-DC) or low frequency high power pulse (HIPIMS) sources. The plasma pre-treatment processes were carried out in an Ar–O 2 atmosphere using either Cu or Ti sputter targets. XPS, AFM and sessile drop water contact angle measurements have been employed to examine changes in surface chemistry and morphology for different pre-treatment process parameters. Deposition of metal oxide onto the PET surface is observed as a result of the sputter magnetron-based glow discharge web treatment. Using the Cu target, both the p-DC and HIPIMS processes result in the formation of a thin CuO layer (with a thickness between 1 and 11 nm) being deposited onto the PET surface. Employing the Ti target, both p-DC and HIPIMS processes give rise to a much lower concentration of Ti (< 5 at.%), in the form of TiO 2 on the PET treated surface. The TiO 2 is probably distributed as an island-like distribution covering the PET surface. Presence of Cu and Ti oxide constituents on the treated PET is beneficial in aiding the adhesion but alone (i.e. without oxygen plasma activation) is not enough to provide very high levels of hydrophilicity as is clear from sessile drop water contact angle measurements on aged samples. Exposure to the plasma treatments leads to a small amount of roughening of the substrate surface, but the average surface roughness in all cases is below 2.5 nm. The PET structure at the interface with a coating is mostly or wholly preserved. The oxygen plasma treatment, metal oxide deposition and surface roughening resulting from the HIPIMS and p-DC treatments will promote adhesion to any subsequent thin film that is deposited immediately following the plasma treatment.

Mechanical and Surface Properties of E-beam Irradiated Polytetrafluoroethylene-Silicone Rubber Composites

Compounding electron beam irradiated polytetrafluoroethylene (PTFE or Teflon) powder with silicone rubber produced silicone rubber/PTFE composites with desired physical properties. PTFE powder was exposed to electron beam irradiation at various doses and characterized by FTIR, DSC and contact angle measurements. Irradiation of PTFE with high energy electron beam induced chain scission reactions. Irradiated PTFE showed higher degree of crystallization and lower melting point with increasing absorbed dose. Number average molecular weight of irradiated PTFE was reduced significantly at higher absorbed doses. Formation of polar groups on the surface of irradiated PTFE powder was detected by FTIR spectroscopy. The latter was also verified by measurements of water-drop contact angle, which decreased with increasing absorbed dose. Mechanical and surface properties of the composites of silicone rubber and PTFE were characterized by tensile strength, abrasion resistance and water drop contact angle measurements. All the composites containing 5–15 phr PTFE showed higher tensile strength compared to the silicone rubber. Irradiation of PTFE powder had a significant effect on improving the abrasion resistance of the silicone rubber upon addition of only 5 phr irradiated PTFE. Similar abrasion resistance was obtained with the addition of higher amounts of non-irradiated PTFE (15 phr). Water drop contact angle of the composites decreased slightly with increasing the absorbed dose of PTFE.