Polar Component Of Surface Free Energy Research Articles

Evaluation of polyphenylene sulfide by surface thermodynamics approaches: Comparison with common polymers

AbstractPoly(phenylene sulfide) (PPS) is an advanced thermoplastic and widely used in industrial applications requiring high performance. Research on improving the surface properties of PPS is still ongoing and a detailed surface free energy (SFE) knowledge of this polymer is necessary for its applications related to surface wettability. In this study, wettability characteristics of PPS were evaluated by SFE calculations. For this purpose, the apparent contact angles of nine different test liquids having various surface tensions were measured on the PPS surface by the sessile drop method. After that, the dispersive and polar components of SFE were calculated using geometric (Owens and Wendt's method) and harmonic (Wu's method) mean approaches. The Lifshitz‐van der Waals, acidic and basic components of SFE were calculated using van Oss‐Chaudhury‐Good method. Additionally, the surface tension values of PPS were also determined by equation of state, Zisman's critical surface tension and Fowkes' approaches. In the present study, the effects of calculation methods and selected liquid pairs on SFE parameters were systematically investigated. It was found that selected liquid pairs and calculation methods affected the SFE considerably. The reasons for this were examined and the SFE components of PPS was compared with some common polymers for better evaluation.

Surface free energy and wettability properties of transparent conducting oxide-based films with Ag interlayer

ITO, ZTO, AZO and Ag are commonly used in transparent conducting oxide (TCO)/metal/TCO electrodes to form multilayered thin films on a suitable substrate. A detailed surface free energy (SFE) knowledge of these films is critical to design desirable TCO-based sandwich structures. In this study, TCO/Ag/TCO multilayer thin films were coated onto glass substrates using ITO, ZTO, AZO and Ag targets by magnetron sputtering. The wettability properties of TCO, Ag interlayer and TCO/Ag/TCO were evaluated by contact angle measurements of seven different liquids having various surface tension values. The dispersive and polar components of SFE were calculated using geometric and harmonic mean approaches. The acidic and basic components of SFE were calculated using van Oss-Chaudhury-Good method. Following this, the work of adhesion values between TCO films and Ag interlayer were estimated using SFE values of the films. The results show that the SFE components of the surfaces differ depending on the TCO type, the total SFE values of TCO/Ag/TCO films were lower than that of TCO films, and AZO/Ag adhesion is stronger than the other TCO/Ag structures. The reasons behind these differences were discussed by evaluating the SFE, XRD, AFM and SEM analysis simultaneously.

Investigating the impact of zeolite on reducing the effects of changes in runoff acidity and the moisture sensitivity of asphalt mixtures

Most studies evaluating the performance of asphalt mixtures against moisture damage use distilled water or drinking water to create wet conditions. However, the main part of the moisture entering the asphalt layers in the pavement is the rainfall runoff that contains dust, soot, and other pollutants absorbed by the pavement surface, which affect the acidity of rainfall runoff. Accordingly, the impacts of water acidity and Zeolite as an environmental pollutant absorbent, as well as a pH moderator of the water entering the asphalt layers, were investigated on the moisture sensitivity of different asphalt mixtures with mechanical and surface free energy (SFE) tests. The results of the mechanical methods revealed that the change in the runoff acidity increases the moisture damage potential of asphalt mixtures. Asphalt cement modification with Zeolite reduced the drop in the tensile strength ratio (TSR) as a result of changing the pH. The application of Zeolite increased the base component of SFE and reduced the acid component of the asphalt cement. The use of Zeolite caused the formation of amorphous chains in the asphalt cement structure, which increased the nonpolar component of SFE. The polar SFE component of the asphalt cement was slightly improved with the incorporation of Zeolite. The utilization of Zeolite increased the free energy of cohesion, thereby increasing the resistance of the asphalt cement film to cohesive failure. In addition, the debonding energy calculations indicated a decrease in this component due to asphalt cement modification. The results of both mechanical and thermodynamic methods illustrated that asphalt cement modification with Zeolite has a positive effect on decreasing the debonding energy and, thus, reducing moisture damage.

Surface free energy analysis of ITO/Au/ITO multilayer thin films on polycarbonate substrate by apparent contact angle measurements

A detailed surface free energy (SFE) knowledge of transparent conducting oxide (TCO)/metal/TCO electrodes is necessary for their applications related to surface wettability. However, SFE analysis of these surfaces has not been performed systematically previously. In this study, ITO and ITO/Au/ITO multilayer thin films were coated onto O2 plasma treated polycarbonate (PC) substrates by magnetron sputtering. The wettability characteristics of untreated PC, O2 plasma treated PC, ITO, Au interlayer, and ITO/Au/ITO multilayer thin films were evaluated by apparent contact angle measurements of nine different test liquids having various surface tensions. Following this, Lifshitz-van der Waals, acidic, basic, dispersive, and polar components of SFE were calculated using acid-base, geometric and harmonic mean approaches. In the present study, in which the significance of calculation methods and selected liquid pairs on SFE parameters were investigated, the effect of Au interlayer presence on SFE parameters were also evaluated simultaneously. The results showed that the total SFE values of ITO/Au/ITO multilayer thin films were found to be higher than that of ITO surface. The reasons behind this difference were discussed in terms of SFE components obtained using various liquid pairs by different methods. The results were also supported with XRD, XPS, AFM, and TEM analysis.

An investigation into the influence of aging and rejuvenation on surface free energy components and chemical composition of bitumen

The present work aims to study the influence of Waste Vegetable Oil (WVO) as a rejuvenator on the properties (physical, chemical and surface free energy (SFE)) of aged bitumen and assess the interaction between rejuvenator and aged bitumen in such blends. The study also investigated the relation between SFE components and SARA (acronym for Saturates, Aromatics, Resins and Asphaltenes) fractions in aged and rejuvenated bitumen. The SARA analysis was carried out by employing Thin-layer chromatography with flame ionisation detection (TLC-FID) technique. The SFE components of the bitumen for both aged and rejuvenated bitumen were determined by measuring the contact angles with different probe liquids using a sessile drop device.The test results on bitumen aged to different construction and in-service conditions suggested that the non-polar component of SFE (γLW) decreases with aging, which is due to a decrease in non-polar saturates and aromatics as demonstrated by TLC-FID analysis. However, the increase of the polar asphaltenes was not reflected in the trend for the polar component of SFE (γ+−) which was attributed to the aggregation of the asphaltenes into clusters in extremely aged bitumen. The findings from the study also suggested that γLW correlates, inversely, well with asphaltenes concentration rather than total SFE (γTotal) (or) γ+−.

Effect of natural ageing on surface of silver loaded TPE and its influence in antimicrobial efficacy

The aim of this study is to characterize the modifications in silver loaded TPE surfaces exposed to weathering and their relation to susceptibility to microbial attack. Silver loaded TPE materials were exposed to natural ageing for nine months and modifications in antimicrobial properties and surface characteristics were evaluated. Chemical changes were investigated by using the infrared spectra. The average surface roughness and topography were determined by atomic force microscopy. Contact angle was measured to verify wettability conditions and surface free energy (SFE). After nine months of exposure, a decrease in the antimicrobial properties of loaded TPE compounds was observed. A reduction in surface roughness and improvement in wettability and high values of polar component of SFE were verified. The best antibacterial action was noticed in the sample with high Lewis acid force, lower roughness and lower carbonyl index.

Dewatering of 2,2,3,3-tetrafluoropropan-1-ol by hydrophilic pervaporation with poly(vinyl alcohol) based Pervap™ membranes

Pervap™ 2200, 2201, 2216, 2255, and 2510 hydrophilic, PVA membranes were investigated in pervaporation of water-tetrafluoropropanol mixtures. Physicochemical properties of membranes were characterized by determining the contact angle (CA) of water and glycerol and the surface free energy (SFE). The separation and transport properties of membranes were determined during vacuum pervaporation in contact with water-TFP mixtures containing up to 22 wt.% water. It was found that all membranes were hydrophilic (CA < 90°) and the polar component of SFE was much higher than the dispersive one. The apparent activation energy for water transport was very high (Eapp = 81.3 kJ/mol), indicated that water transport is activated thermally. Pervap™ membranes were very selective during the dehydration process of TFP. In contact with the Pervap™ 2200, 2201, and 2216 permeate contained practically pure water, regardless the feed composition. The process separation index (PSI) for Pervap™ 2200 and 2216 was close to 5000 kg m−2 h−1, suggesting that both membranes can be efficiently applied in the batch pervaporation process for TFP dehydration.

The influence of “small molecules” on properties of TiO2 films prepared by sol–gel method

The sol–gel method was used for preparation of TiO2 sols without and with the addition of “small molecules” — acetylacetone and acetic acid. The TiO2 films were made by dip-coating method in different time intervals after preparation of sols. Properties of film surface, such as morphology, rms-roughness and adhesion force were studied using atomic force microscopy (AFM). The contact angle of water and diiodomethane was measured for identification of polar and dispersion component of the surface free energy (SFE). From the obtained results, it can be seen that “small molecules” influence the morphology of films. During the first days after the sol preparation, there is the increase of roughness of films prepared from sols with “small molecules” but with the increasing time, the roughness decreases. There is no crystallization of films with acetylacetone. For films prepared from sols with acetylacetone, the polar component of SFE is lower than in the case of films prepared from sols without “small molecules” and with acetic acid. The “small molecules” decrease the stiffness and adhesion force mainly for films prepared several days after sol preparation. This influence is the result of complex effect of “small molecules” on processes occurring during preparation of films, from hydrolysis reaction over process of particle growth to thermal treatment.

Effect of functionalized lignin on the properties of lignin–isocyanate prepolymer blends and composites

Functionalization of lignin was carried out with 4,4′-diphenyl methane diisocyante (MDI) at 90°C for 60min. Formation of the resulting reaction products was confirmed with the help of FTIR, FESEM–EDAX and DSC. Polymer blends were prepared using an isocyanate prepolymer (NCO/OH: 3.5) and functionalized lignin (up to 15wt%) and evaluated their phase miscibility, wettability, rheology and mechanical properties. Under DMA run, the maximum storage and loss moduli of blends were observed at 5wt% lignin content. Wettability results indicated that as the lignin content increased in the blends, the contact angle of probe liquids on the substrate increased while polar component of surface-free energy decreased affecting their wettability. FTIR spectra of the blends showed disappearance of –NCO peak at 2270cm−1 supported its consumption in the network formation. Rheological test revealed that lignin-prepolymer blends needed more stress to flow and also had more viscosity recovery compared with the parent system. The single-lap joint shear strength of blends was higher with the aluminium substrate than the wood. The pull-off adhesive strength of blend at 5wt% lignin content was ∼19% more than the parent prepolymer. The composites made with isocyanate blend and pine needles exhibited acceptable properties as specified in the standard (EN 312).

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.

Surface Free Energy and 7075 Aluminium Bonded Joint Strength Following Degreasing Only and Without Any Prior Treatment

Adhesion is a surface phenomenon occurring in many processes, e.g., bonding, painting or varnishing. Knowing the adhesion properties is critical for evaluating the usability or behaviour of materials during these processes. Good adhesion properties favour the processes of bonding, resulting in high strength of adhesive joints. Adhesive bonded joints are used in many industries, and the subject of this study was 7075 aluminium alloy sheet bonded joints as typically used in the aviation or construction industry. Surface free energy (SFE) can be used to determine the adhesion properties of the materials. The SFE of the tested sheets was determined with the Owens–Wendt method, which consists in determining the dispersion and polar components of SFE. The purpose of this work was to correlate the bonded joint strength of selected aluminium alloy sheets to the surface free energy of the sheets that had been subjected to degreasing only and no other prior treatment was used. Single-lap bonded joints of 7075 aluminium alloy sheets were tested. Higher joint strength was measured for the thinner sheets, while the lowest strength was measured for the thickest sheets. This suggests that the thickness of the joined parts is an important factor in the strength of bonded joints. The comparison of adhesion properties to the strength of adhesive joints of tested materials shows that there is no direct relation between good adhesion properties (i.e., high SFE) and joint strength. As for degreasing, the highest joint strength was observed for aluminium alloy sheets with the lowest SFE; the sheets which were not degreased gave the highest SFE and highest joint strength.

The Application of Grey System Theory to Correlate Chemical Composition and Surface Free Energy of Asphalt Binders

Grey correlation analyses were carried out to determine which chemical components and chemical elements of asphalt binders are most related to surface free energy (SFE) measurements of asphalt binders. The total, dispersive, and polar SFE values were calculated for 23 Strategic Highway Research Program (SHRP) asphalt binders based on contact angle measurements by the sessile drop method and the chemical composition data of the 23 binders was obtained from previously published information. During the Grey correlation analysis, it was found that polar aromatics content has the largest effect on the total SFE and dispersion component of SFE, whereas saturates made the largest contribution to the polar component of SFE. Carbon (C) and hydrogen (H) made the largest contribution to the total, dispersion, and polar SFE; vanadium (V) content has the smallest effect on the total surface free energy, including its dispersion and polar parts.

A modification of superficial properties of materials by means of application of multiple coatings for their use in orthopaedics

The article analyses studies of surface parameters of different multiple coatings, such as: TiN, CrN, (Ti,Cr)N, TiN/TiC10N90, TiN/TiC20N80, which are applied by the arc method (Arc-PVD) on stainless steel samples (1H18N9), and the same coatings with an additional oxide layer Al2O3, which are deposited by the method of reactive magnetron sputtering (RMS method). A comparative analysis of the thickness, roughness and structural characteristics of surfaces was carried on. Other parameters, such as surface wettability (water receptivity / water repellency), surface free energy (SFE) and fractional polarity, were determined by methods of Wu, Owens-Wendt-Rabel-Kaelble, Van Oss and Fowkes. In order to make a further conclusion about an effect of the above factors on biological objects, in vitro experiments were carried out for studying relationships between cell structures and the material in fibroblast cultures. The results show some correlation between the surface properties of the materials and adhesion and proliferation of the cell cultures. Better biological parameters of the response (the total number of cells, proliferation, morphology of cells) were received in case of coatings with higher values of the polar components of SFE and fractional polarity.

Effects in Surface Free Energy of Sputter-Deposited TaNx Films

TaNx thin films have attracted much attention for semiconductor integrated circuit (IC) packaging molding dies and forming tools due to their excellent hardness and thermal stability. Tantalum nitride (TaNx) thin films with TaN, TaN, TaN, TaN, and TaN were prepared using radio frequency (RF) sputter. The experimental results showed that the contact angle at 20 C go up with raising content to 119.2 at beginning, corresponding to TaN, and then drop off. In addition, the contact angle components decreased with increasing surface temperature. Because increasing surface temperature disrupts the hydrogen bonds between water and the films and water vaporize gradually. The total surface free energy (SFE) at 20 C decrease with content to raise to 39.6 mN/m(TaN) at the start, and then increase. A larger contact angle means a weaker hydrogen bonding, resulting in a lower SFE. The polar SFE component has same trend with total SFE, but the dispersive SFE component is on the contrary exactly. The polar SFE component is also lower than the dispersive SFE component. This results from hydrogen bonding being polar. The total SFE, dispersive SFE, and polar SFE of TaNx films decreased with increasing surface temperature. This is because water evaporation on the surface, disrupted hydrogen bonds, and surface entropy increase with increasing temperature. The film roughness has an obvious effect on the SFE and there is a tendency for the SFE to increase with increasing film surface roughness. SFE and surface roughness can be expressed as a function in direct ratio.

Effects in Surface Free Energy of Sputter-Deposited MoNx Films

MoNx thin films have attracted much attention for semiconductor IC packaging molding dies and forming tools due to their excellent hardness, thermal stability. MoNx thin films with MoN0.57, MoN0.96, MoN1.48, MoN2.07, MoN2.44 were prepared using radio frequency (RF) sputter. The experimental results showed that the contact angle at 20 °C go up with raising N2 content to 106.4° at beginning, corresponding to MoN2.07, and then drop off. In addition, the contact angle components decreased with increasing surface temperature. Because increasing surface temperature disrupts the hydrogen bonds between water and the films and water vaporize gradually. The total surface free energy (SFE) at 20 °C decreases with N2 content to raise to 33.8 mN/m (MoN2.07) at the start, and then increases. Because a larger contact angle means that a weaker hydrogen bonding, resulting in a lower SFE. The polar SFE component has same trend with total SFE, but the dispersive SFE component is on the contrary exactly. The polar SFE component is also lower than the dispersive SFE component. This is resulting from hydrogen bonding being polar. The total SFE, dispersive SFE, and polar SFE of MoNx films decreased with increasing surface temperature. This is because water evaporation on the surface, disrupted hydrogen bonds and surface entropy increasing with increasing temperature.

Relationship between surface properties (roughness, wettability) of titanium and titanium alloys and cell behaviour

Cell attachment and spreading to titanium-based alloy surfaces is a major parameter in implant technology. In this paper, substratum surface hydrophobicity, surface free energy, interfacial free energy and surface roughness were investigated to ascertain which of these parameters is predominant in human fibroblast spreading. Two methods for contact angle measurement were compared: the sessile drop method and the captive bubble two-probe method. The relationship between surface roughness and the sessile drop contact angles of various engineered titanium surfaces such as commercial pure titanium (cp-Ti), titanium–aluminium–vanadium alloy (Ti–6Al–4V), and titanium–nickel (NiTi), was shown. Surface free energy (SFE) calculations were performed from contact angles obtained on smooth samples based on the same alloys in order to eliminate the roughness effect. SFE of the surfaces have been calculated using the Owens–Wendt (OW) and Van Oss (VO) approaches with the sessile drop method. The OW calculations are used to obtain the dispersive ( γ d) and polar ( γ p) component of SFE, and the VO approach allows to reach the apolar ( γ LW) and the polar acid–base component ( γ ab) of the surface. From captive bubble contact angle experiments (air or octane bubble under water), the interfacial free energy of the different surfaces in water was obtained. A relationship between cell spreading and the polar component of SFE was found. Interfacial free energy values were low for all the investigated surfaces indicating good biocompatibility for such alloys.

Surface free energy characterization of vernix caseosa. Potential role in waterproofing the newborn infant.

Vernix caseosa is a proteolipid biofilm synthesized by the human fetus, which progressively covers the fetal skin surface during the last trimester of pregnancy. The exact physiological functions of vernix are unclear. Hypothetically, it serves a role in "waterproofing" the fetus during the critical period of epidermal barrier development before birth. Vernix may also play a role in adaptation of the fetal skin surface to the dry, cool extrauterine environment after birth. Given the strategic position of vernix on the fetal skin surface and the rapidly changing environment encountered by the skin at birth, we proposed that investigation of vernix surface characteristics would facilitate understanding its putative physiological roles. In this paper, we focused on the determination of the surface free energy (SFE) of vernix caseosa. Different approaches were used to calculate the SFE of vernix from contact angle (theta) measurements between vernix and various liquids (benzyl alcohol, diiodomethane, glycerol, and water). The critical surface tension (CST) of vernix was calculated using Zisman plots. The dispersive and the polar components of vernix SFE were calculated using the Owens-Wendt geometric mean method. Vernix was contrasted with petrolatum, a commonly used skin protectant. CST of fresh vernix was 40.5 dyne/cm while that of petrolatum was 35.8 dyne/cm. Fresh vernix polar SFE was 1.5 dyne/cm while petrolatum had almost no polar SFE component (0.03 dyne/cm). For all liquids (except the nonpolar diiodomethane) there was a significant decrease in contact angle with time. The CST and the total SFE values suggest that vernix has very low surface energy and is highly unwettable. These findings are significant insofar as the main component in vernix is water, which is highly energetic. Although vernix has a very high water content, the major part of its SFE is hydrophobic (dispersive). The limited interaction between vernix and hydrophilic liquids supports the hypothesis that vernix acts as a natural protectant cream to "waterproof" the fetus in utero while submerged in the amniotic fluid.

Studies on adsorptive interaction between natural fiber and coupling agents

Efficacy evaluation of various coupling-agent-treated sisal fibers was made by contact angle measurements and Fourier transform infrared spectroscopy. It was found that high contact angle and reduced hydroxyl groups on titanate-treated fibers favor its better hydrophobicity over the other treatments. The presence of adsorbed layer of coupling agent on the fiber surface was ascertained by appearance, shifting, and decreased intensity of absorption bands. The lowest polar component of surface-free energy for N-substituted methacrylamide-treated fiber indicates the formation of ordered layers of its organofunctionality at the surface. The reason for enhanced interaction between sisal fiber and N-substituted methacrylamide is suggested by the formation of hydrogen bond, besides extracting a surface-active proton from the fiber surface by alkoxy group to form a covalent bond. An optimum treating condition of fiber for effective adsorptive interaction has been reported. The deposition of compound in the form of an aggregate on the fiber surface was also observed under scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1847–1858, 1998

Studies on adsorptive interaction between natural fiber and coupling agents

Efficacy evaluation of various coupling-agent-treated sisal fibers was made by contact angle measurements and Fourier transform infrared spectroscopy. It was found that high contact angle and reduced hydroxyl groups on titanate-treated fibers favor its better hydrophobicity over the other treatments. The presence of adsorbed layer of coupling agent on the fiber surface was ascertained by appearance, shifting, and decreased intensity of absorption bands. The lowest polar component of surface-free energy for N-substituted methacrylamide-treated fiber indicates the formation of ordered layers of its organofunctionality at the surface. The reason for enhanced interaction between sisal fiber and N-substituted methacrylamide is suggested by the formation of hydrogen bond, besides extracting a surface-active proton from the fiber surface by alkoxy group to form a covalent bond. An optimum treating condition of fiber for effective adsorptive interaction has been reported. The deposition of compound in the form of an aggregate on the fiber surface was also observed under scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1847–1858, 1998

Adhesion Mechanisms of Polyurethanes to Glass Surfaces. III. Investigation of Possible Physico-Chemical Interactions at the Interphase

Abstract Surface free energies of polyurethanes made from toluene diisocyanate and 1, 4 butanediol-based hard segments and caprolactone polyol-based soft segments were calculated using additive functions. Good agreement was found between the calculated values based on additive functions and the calculated values based on contact angle measurements. The phase-separated polyurethanes were found to have a higher polar surface free energy component (γP). This was linked to the preferential segregation of butanediol/butanediol-derived moieties to the polyurethane surfaces due to phase separation. The adhesion values of these polyurethanes to soda-lime glass were correlated with their respective γP values and a linear relationship was found. It was also shown that the adhesion values of the low γP polyurethanes improved substantially when the glass surfaces were coated with a thin layer of butanediol prior to the bonding. The modulus of the interphase region rich in butanediol was evaluated. Although a modulus increase was found at the interface, this increase was found to play a secondary role in the adhesion. The chemical interactions at the polyurethane/glass interphase were investigated by pre-treating the glass surfaces with methyl-trimethoxysilane and trimethylchlorosilane prior to adhesion testing. The adhesion data showed no significant difference between the uncoated and the silane-treated glass substrates. Based on this experimental evidence, the possibility of any covalent or ionic bonding at the polyurethane/glass interphase was assumed negligible. It was determined that the mechanism of adhesion between the polyurethanes and the glass surface could be through the formation of an interphase region in which hydrogen bonding between the butanediol-rich interphase region and the hydroxylated glass surface plays a key role.