Component Of Surface Free Energy Research Articles

Mechanistic Evaluation of the Effect of WMA Additives on Wettability and Moisture Susceptibility Properties of Asphalt Mixes

Abstract This study used a mechanistic framework (i.e., surface free energy) to evaluate the moisture susceptibility of warm mix asphalt (WMA) with three different WMA additives, namely, Sasobit, Advera, and Evotherm. The surface free energy (SFE) components of modified PG64-22 asphalt binder with different percentages of WMA additives and selected aggregates were measured in the laboratory. The wettability, the work of adhesion, the work of debonding, and energy ratios were estimated in order to assess the moisture-induced damage potential of combinations of modified asphalt binders and different aggregates. The results indicate that Sasobit and Advera are able to reduce the moisture susceptibility potential of the mixes, but their use is not recommended with highly acidic aggregates such as granite. Evotherm resulted in the highest increases in wettability, total surface free energy, and increased work of adhesion and a reduction in the work of debonding, resulting in a better possible aggregate coating with asphalt binder and lower moisture susceptibility with all types of tested aggregates relative to those of other WMA additives. Furthermore, tensile strength ratio (TSR) tests were conducted on Advera and Evotherm-modified and neat (unmodified) asphalt mixes, and the results were compared with those from the SFE test. It was found that the SFE approach is a better indicator of moisture susceptibility than the traditional TSR test. The findings of the present study would help the highway engineers and agencies to better understand the moisture damage potential of flexible pavements constructed with WMA technologies.

Comparative Analysis of Energetic Properties of Ti6Al4V Titanium and EN-AW-2017A(PA6) Aluminum Alloy Surface Layers for an Adhesive Bonding Application

The purpose of this article is to present energetic properties of surface Ti6Al4V titanium as well as surface EN-AW-2017A(PA6) aluminum alloy layers. Values of surface free energy after selected mechanical operations and ozonation were compared. In addition, the influence of different values of ozone concentration on surface layer energetic activation was analyzed. Dispersive and polar components of surface free energy were of particular concern. Comparative evaluation of shearing strength of Ti6Al4V titanium and EN-AW-2017A(PA6) aluminum alloy single-lap adhesive bonded joints were presented. Results can be used as pro-ecological methods of titanium and aluminum alloys preparing for applications where adhesive phenomenon is important.

Water repellency enhances the deposition of negatively charged hydrophilic colloids in a water-saturated sand matrix

The effect of grain water repellency on transport and deposition of hydrophilic colloids was studied by analyzing the breakthrough behavior of carboxylate-modified microspheres in water-saturated wettable and hydrophobic sand columns at different ionic strengths. Interaction free energies calculated from zeta (ζ)-potential and contact angle data were used to explain the specific colloid breakthrough behavior. Experimental breakthrough data could be well described with the finite-element code HYDRUS-1D using a one kinetic site model with attachment and detachment kinetics. Higher colloid deposition rates found for the hydrophobic sand could primarily be explained by its small electron-donor component of surface free energy (γs−=1.6×10−2mJm−2, compared to γs−=64.1mJm−2 for the wettable sand), leading to strongly attractive acid–base interactions at separation distances<5nm. Increasing ionic strength reduced the repulsive electrostatic interactions and generally increased colloid deposition with the effect being more pronounced in the hydrophobic sand. It can be concluded that grain water repellency tends to increase the deposition of negatively charged hydrophilic colloids, which can be ascribed to specific acid–base interactions. However, our results further revealed that the calculated interaction free energy profiles should be considered only as an approximation showing general trends because surface chemical heterogeneity as detected by atomic forces microscopy impeded the determination of the actual interaction energy conditions, resulting in an overestimation of electrostatic repulsion.

Spray dried chitosan–EDTA superior microparticles as solid substrate for the oral delivery of amphotericin B

The present investigation was aimed at synthesis of chitosan–EDTA superior microparticles (COECH) bearing high oil adsorbing and oil desorbing properties. These superior particles were prepared by thermal amide conjugation of COO− group of EDTA with NH2 group of chitosan employing spray-drying technique. The synthesis was optimized using 42 full factorial design. The particles showed high oil adsorbing capacity as well as oil desorbing capacity with enhanced dispersive components of surface free energy as compared to Aerosil 200. In addition, these COECH microparticles showed higher amphotericin B loading capacity, enhancement in the in vitro dissolution performance (12-fold) and produces nanoemulsion in the size range of 70–90nm. Further, the results were in consonance with those observed during ex vivo performance. Thus, the findings revealed simple synthesis of COECH microparticles that showed superior properties of solid substrate for the development of amphotericin B nanoemulsion.

Ethylenediaminediacetic acid bis(carbido amide chitosan): Synthesis and evaluation as solid carrier to fabricate nanoemulsion

We have optimized the synthesis of spray dried ethylenediaminediacetic acid bis(carbido amide chitosan) (ED-chitosan) microparticles employing 32 full factorial design. The ED-chitosan microparticles were characterized using FTIR-ATR, DSC analysis, oil adsorbing capacity, oil desorbing capacity, surface free energy and dynamic advancing contact angle. The ED-chitosan microparticles were found to have enhanced dispersive component of surface free energy as compared to Aerosil 200. However, they showed lower polar component. This was associated with similar oil adsorbing capacity but higher desorbing capacity. The SEM analysis supported ability of ED-chitosan microparticles to completely spread lipophillic drug over its surface. The reconstituted nanoemulsion generated from ED-chitosan was stable (neutral zeta potential), spherical shaped and 110nm size (TEM analysis). Further, these nanoemulsions when prepared with primaquine were successfully enhanced in vitro dissolution and its ex vivo performance. Thus, the study showed new possibilities of industrial acceptance of ED-chitosan microparticles as a solid carrier for the fabrication of nanoemulsion.

Surface modification of indium tin oxide for direct writing of silver nanoparticulate ink micropatterns

Surface treatment techniques were deployed to alter the surface of indium tin oxide (ITO) samples to attain a favorable interface between printed nano-inks and ITO surface. Surface free energy components of treated ITO substrates were calculated for each treatment using the van Oss–Chaudhury–Good method. The surface treatments of ITO changed the Lifshitz–van der Waals and Lewis acid–base components, and contact angle hysteresis significantly. Among all the surface treatments, air plasma treated samples showed high polar in nature, whereas dodecyltrichlorosilane self-assembled monolayer treated sample showed the lowest. In addition to the polarity and homogeneity, the surface roughness of the ITO was studied with respect to the surface treatment. Silver nanoparticulate ink was printed on treated ITO surfaces using aerosol jet printing system. Printed silver nano-ink line width and morphology strongly depended on the surface treatment of the ITO, ink properties and printing parameters.

Tunable surface free energies of functionalized molecular layers on Si surfaces for microfluidic immunosensor applications

Enhanced antigen–antibody interactions in microfluidic immunosensors can be effected by tailoring the surface free energies of the antibody immobilized surfaces to obtain the appropriate fluid–wall interactions. We report a systematic study to evaluate the surface free energies from contact angle measurements, using the LWAB method, of different antibody (anti-BSA, anti-PSA, and anti-CRP) surfaces, each immobilized separately on to non- and nanotextured Si surfaces via a stack of functionalized layers including aminosilanes of which three different types were used. The apolar surface free energy components were independent of the physical modification in the non-functionalized and the intermediate hydrolyzed surfaces where as they depended on the nature of the surface and the chemical modifications in the subsequent functionalized stages. Surface free energies of the different antibodies immobilized with the shorter chain length aminosilane (APTES) on non- and nanotextured surfaces were in the order of anti-BSA<anti-PSA<anti-CRP. A tunability of the surface free energy up to 9.6mJ/m2 was achieved which is reasonably significant when compared to the surface free energy window (Δγs=40mJ/m2) of biofunctionalized surfaces. This fundamental understanding of the surface energetics of the biofunctionalized surfaces can be utilized in modulating the surface properties to design efficient immunosensors.

Relationship between Surface Free Energy of Underlying Layers and O3-TEOS Chemical Vapor Deposition

In this study, we clarify the relationship between the surface free energy (SFE) of the underlying layers and O3-tetraethylorthosilicate (TEOS) chemical vapor deposition (CVD) film formation. Thermal SiO2, chemical SiO2 or plasma enhanced TEOS (PE-TEOS) SiO2 film is used as the underlying layers. SFE measurement was performed using the Owens-Wendt approach. We found that a direct correlation does not exist; however, the tendency of a proportional relationship could exist between the polar component of SFE and the O3-TEOS CVD rate. The O3-TEOS CVD rate decreased as the polar component of SFE decreased for the surface pretreated with organic solvents.

Calculation of Intraocular Lens Surface Free Energy and its Components from Contact Angle Measurements

One of the most important biomaterial characteristics involved in bacterial adhesion on intraocular lenses (IOLs) is hydrophobicity. We calculated the hydrophobicity parameters of IOLs made of 6 different materials (polymethylmethacrylate, PMMA, heparin surface-modified PMMA, HSM-PMMA, silicone, hydrophilic and hydrophobic acrylics and collamer). Values of IOL surface free energy components were determined from contact angle measurements, using the Fowkes, Owens-Wendt and Good-van Oss calculations. Contact angles were higher for silicone and hydrophobic acrylic materials and lower for collamer and hydrophilic acrylic materials. The values of IOL surface free energy components obtained with the 3 different calculations were homogenous. According to the Owens-Wendt calculation, the IOLs could be separated into dispersive implants (hydrophobic acrylic, silicone and PMMA) and polar implants (collamer, hydrophilic acrylic and HSM-PMMA).

Biocompatibility of poly(lactic acid) with incorporated graphene-based materials

The incorporation of graphene-based materials has been shown to improve mechanical properties of poly(lactic acid) (PLA). In this work, PLA films and composite PLA films incorporating two graphene-based materials – graphene oxide (GO) and graphene nanoplatelets (GNP) – were prepared and characterized regarding not only biocompatibility, but also surface topography, chemistry and wettability. The presence of both fillers changed the films surface topography, increasing the roughness, and modified the wettability – the polar component of surface free energy increased 59% with GO and decreased 56% with GNP. Mouse embryo fibroblasts incubated with both fillers exceeded the IC50 in both cases with a concentration of 10μgmL−1. No variations in cell proliferation at the surface of the composite films were observed, except for those containing GO after 24h incubation, which presented higher cell proliferation than pristine PLA films. Platelet adhesion to PLA and PLA/GNP films was lower in the presence of plasma proteins than when no proteins were present. Furthermore, incorporation of GNP into PLA reduced platelet activation in the presence of plasma proteins.The results indicated that low concentrations of GO and GNP may be incorporated safely in PLA to improve aspects relevant for biomedical applications, such as mechanical properties.

Contact angle analysis of corona treated polypropylene films

In this work, the effect of the surface modification of polypropylene films via corona treatment was investigated. Polypropylene films were treated with negative and positive corona discharge, at atmospheric pressure, for 5 minutes, at two different temperatures – 25 °C and 90 °C. The changes in the surface free energy were investigated by means of contact angle measurements. The Bickerman's method was applied to determine the polar and dispersion components of the polymer surface free energy, on the basis of the theory of Owens, Wendt, Kaelble and Uy. Atomic force microscopy was used to analyze the polymer surface morphology changes of the films with temperature. According to the findings, in all cases the corona treatment increases the surface free energy of polypropylene films and its polar part, in comparison with the untreated samples. The effects of negative and positive corona polarities display some specific features which could be associated with different charged group introduced onto the film surface during the corona treatment. The total final effect depends on the simultaneous action of the two competing factors – temperature and corona polarity. The most pronounced effect was observed for high temperature negative corona treatment.

Effects of liquid viscosity, surface wettability and channel geometry on capillary flow in SU8 based microfluidic devices

The capillary flow in SU8 based microfluidic devices fabricated in SF-100 by lithographic technique has been recorded and analysed in this report. Leakage free microfluidic flow is achieved by indirect bonding between polymethyl methacrylate (PMMA) coated glass lid surface and SU8 channel substrate during hard baking. The working liquids are dyed ethylene glycol, dyed ethanol, dyed isopropyl alcohol (IPA) and dyed liquid mixture (water and IPA). The capillary flow of dyed ethylene glycol is found to be slower in each device due to higher viscosity and lower surface wettability as compared to other working liquids. Square SU8 micropillar arrays (80μm and 120μm of side lengths) are fabricated on the glass bottom wall surface of SU8 based microchannel. The capillary flow of any particular working liquid is observed to be faster through the square micropillars of smaller side length due to their lower surface area to volume ratio in the device. Also, the capillary flow of polar liquids is found to be faster on the microchannel surface of higher polar component of surface free energy. The above results are highly significant to control the speed of capillary flow in lab-on-a-chip systems.

Investigation of the surface properties of POSS-modified polyacrylate by inverse gas chromatography

AbstractThe surface properties of poly(methyl methacryl-ate-co-n-butyl methacrylate-co-cyclopentyl methacryloxy propyl-polyhedral oligomeric silsesquioxane) (poly(MMA-co -BMA-co-POSSMA)) were studied by means of inverse gas chromatography (IGC) using 10 non-polar and polar solvents as the probes. Thermodynamic parameters of adsorption, such as the dispersive component of the surface energy, the specific interaction contribution to the free energy of adsorption and the acid/base constants of polymer surface were determined. It was found that incorporation of POSSMA into polymer resulted in increasing interactions between polymers and solvents, dispersive component of surface free energy of polymer and acidity of the surfaces of the polymers. The more the POSSMA were embedded, the larger the dispersive component of the surface free energy was, and the acidic character of the polymer surface was more obvious.

Effect of physical adhesion on mechanical behaviour of bamboo fibre reinforced thermoplastic composites

Systematic experimental results describing the dynamic wetting properties of bamboo fibres were analysed by applying the molecular-kinetic theory of wetting. Results suggest that the bamboo fibre surface represents a well-defined system for wetting analysis. The surface free energy components were calculated according to the acid–base theory. These values were then used to calculate the theoretical work of adhesion, spreading coefficient, wetting tension, and interfacial energy. The wetting behaviour of various thermoplastic matrices (polypropylene, maleic anhydride-grafted polypropylene, polyvinylidene-fluoride, and polyethylene-terephthalate) was characterized. Surface chemical components were identified using XPS. Additionally, transverse 3-point bending tests and single fibre pull-out tests were performed. This integrated physical–chemical–mechanical approach was used to study the effect of adhesion on the mechanical strength of thermoplastic composites reinforced with bamboo, showing that increase in physical adhesion can explain the improved interfacial and longitudinal strength in bamboo polyvinylidene-fluoride (PVDF) composites compared to the other thermoplastic matrices used in this study. Surface energy components of bamboo fibres and PVDF were matched, resulting in an improvement of the physical adhesion.

Biodegradacja poli(estrouretanow) w symulowanych warunkach kompostowania

Polyurethanes synthesized in a two-step polyaddition process of trimethylhexamethylene diisocyanate (TMDI), poly(e-caprolactone) diols with different molecular weights (PCL 750, PCL 1250) and glycerol (GLI) were biodegraded under simulated composting conditions with the use of vermiculite as an inert solid medium. Biodegradation process was carried out over a period of 42—106 days. The degree of biodegradation was determined on the basis of weight loss of the samples as well as the changes in the roughness parameters and surface free energy components (SEP). The mechanical properties of the samples before and after degradation were also determined. Additionally, changes in the surface appearance of the samples after composting at simulated conditions were documented using both optical and confocal microscopy. It was found that even after six weeks of biodegradation a significant deterioration of the samples took place.

Wetting of carbon fibers by coal-tar pitch melts

The wettability of carbon fibers from different manufacturers with finish, rinsed of finish, and heat treated at 2000°C by the model liquids water and octane was studied comprehensively. The polar and dispersion components of the carbon-fiber surface free energy were calculated. It was shown that finished fiber had a polar nature whereas removal of the finish could increase or decrease the surface polarity. This could be related to the fiber preparation method. The surface tension of pitch melts was measured and factored into its components. It was shown that the contribution of the polar component to the pitch surface tension was always at least 50% for the studied pitches. The surface tension correlated well with the pitch viscosity but was not related to the softening temperature. Edge wetting angles of the carbon fibers by pitch were calculated based on the experimental results. Fibers for which the contribution of the surface-energy polar component was greater demonstrated better wettability.

A method for determining surface free energy of bamboo fiber materials by applying Fowkes theory and using computer aided machine vision based measurement technique

The purpose of this study is to develop a standard methodology for measuring the surface free energy (SFE), and its component parts of bamboo fiber materials. The current methods was reviewed to determine the surface tension of natural fibers and the disadvantages of techniques used were discussed. Although numerous techniques have been employed to characterize surface tension of natural fibers, it seems that the credibility of results obtained may often be dubious. In this paper, critical surface tension estimates were obtained from computer aided machine vision based measurement. Data were then analyzed by the least squares method to estimate the components of SFE. SFE was estimated by least squares analysis and also by Schultz’ method. By using the Fowkes method the polar and disperse fractions of the surface free energy of bamboo fiber materials can be obtained. Strictly speaking, this method is based on a combination of the knowledge of Fowkes theory. SFE is desirable when adhesion is required, and it avoids some of the limitations of existing studies which has been proposed. The calculation steps described in this research are only intended to explain the methods. The results show that the method that only determines SFE as a single parameter may be unable to differentiate adequately between bamboo fiber materials, but it is feasible and very efficient. In order to obtain the maximum performance from the computer aided machine vision based measurement instruments, this measurement should be recommended and kept available for reference.

Inversion gas chromatography in studies of adsorption properties of carbon materials. Specific component of the surface free energy

Inversion gas chromatography was used to determine at extremely low surface coverages the specific component Isp of the surface free energy for various types of carbon blacks. It was demonstrated that the Rohrschneider-McReynolds model can be used to evaluate the capacity of carbon adsorbents for various kinds of intermolecular interactions.

Use of Surface Free Energy Method to Evaluate Effect of Hydrate Lime on Moisture Damage in Hot-Mix Asphalt

One of the convenient approaches to decreasing moisture sensitivity in hot-mix asphalt (HMA) is coating the aggregate surface with a suitable agent. Hydrate lime (HL) is the most common antistrip additive used to treat aggregate properties in hot-mix asphalt. In this study, the effect of HL-treated aggregate on moisture sensitivity of HMA was evaluated by applying thermodynamic concepts and surface free energy (SFE) method. The SFE components of aggregates and asphalt binders were evaluated by using a universal sorption device (USD) and dynamic Wilhelmy plate method (DWPM), respectively. The results showed that the use of HL reduced the acid SFE and increased the base SFE of the two types of aggregates used in this study. These changes promote adhesion between asphalt binder and aggregate with and without water, particularly in the mixtures containing acidic aggregates prone to moisture damage. Covering the aggregate with HL decreased the total SFE of aggregate, leading to the increase in wetability of asphalt binder over the aggregate. Moreover, HL decreased the difference between surface free energies of asphalt-aggregate and water-aggregate, decreasing the detachment tendency of asphalt binder over the aggregates. Finally, the treatment of aggregate surface with HL reduced the difference between the free energy of adhesion of aggregate-asphalt binder in dry and wet conditions, decreasing the rate of moisture damage.

Mechanism of enhanced wettability of nanocrystalline diamond films by plasma treatment

The mechanism of wetting behavior of nanocrystalline diamond films is examined in terms of surface free energy, morphology, and bonding characteristics. The films are prepared by microwave plasma-enhanced chemical vapor deposition using Ar-rich/N2/CH4 and Ar-rich/H2/CH4 mixtures, followed by microwave hydrogen and oxygen plasma exposures separately. Contact angle measurement with water, ethylene glycol, and formamide reveals that both the as-deposited and hydrogen plasma treated films are hydrophobic, while the oxygen plasma treated film is extremely hydrophilic such that the contact angle is reduced down to almost zero degree. Fourier transform infrared spectroscopy reveals that the hydrogen atoms are dominantly bonded to diamond and amorphous sp3-bonded carbon, and they are removed by the oxygen plasma treatment. For the oxygen plasma treated film, the mean value of oxygen concentration for the top surface to bulk (~1μm) measured by energy-dispersive X-ray spectroscopy is ~10at.%, while that for the top several monolayers surface measured by X-ray photoelectron spectroscopy is much higher at ~37at.%, indicating a higher degree of oxidation toward the surface. The carbon bonding state in the oxidized layer is disordered by incorporation of a large amount of oxygen in form of polar CO bonds, which is accountable for a greater polar component of the apparent surface free energy and stronger dipole–dipole interactions.