Reduction In Contact Angle Research Articles

Improvement in the Microbial Resistance of Resin-Based Dental Sealant by Sulfobetaine Methacrylate Incorporation.

Prevention of dental caries is a key research area, and improvement of the pit and fissure sealants used for caries prevention has been of particular interest. This report describes results of incorporating a zwitterion, sulfobetaine methacrylate (SB), into photo-polymerized resin-based sealants to enhance resistance to cariogenic bacteria and protein adhesion. Varying amounts (1.5–5 wt%) of SB were incorporated into a resin-based sealant, and the flexural strength, wettability, depth of cure, protein adhesion, bacterial viability, and cell cytotoxicity of the resultant sealants were evaluated. The flexural strength decreased with the increasing SB content, but this decrease was statistically significant only for sealants containing ≥3 wt% SB. Incorporating a zwitterion led to a significant reduction in the water contact angle and protein adhesion. The colony-forming unit count showed a significant reduction in the bacterial viability of S. mutans, which was confirmed with microscopic imaging. Moreover, cell cytotoxicity analysis of SB-modified sealants using an L929 fibroblast showed a cytotoxicity comparable to that of an unmodified control, suggesting no adverse effects on the cellular metabolism upon SB introduction. Hence, we conclude that the addition of 1.5–3 wt% SB can significantly enhance the inherent ability of sealants to resist S. mutans adhesion and prevent dental caries.

Preparation, Antimicrobial Properties, and Cytotoxicity of Acrylic Resins Containing Poly(diallyldimethylammonium chloride).

To design and analyze the biologic properties (antibacterial and antifungal, as well as cytotoxicity) of a dental biomaterial based on incorporation of the biocide poly(diallyldimethylammonium chloride) (PDADMAC) into the masses of self- and thermopolymerizable acrylic resins. PDADMAC was diluted into tetrahydrofuran (4 wt%) and incorporated into self- and thermopolymerizable acrylic resins. PDADMAC inclusion was verified by measuring the contact angle with water droplets. Plain resins were used as controls. The antibacterial activity was evaluated against Staphylococcus aureus (ATCC 6538P) and Escherichia coli (ATCC 8739), and the antifungal activity was tested against Candida albicans (ATCC 10231) and Aspergillus niger (ATCC 16404). The cytotoxicity of substances leached from these materials was analyzed in human dental pulp stem cells using MTT reduction assay. Reduction of contact angle confirmed the incorporation of PDADMAC in the resins. Both resins containing PDADMAC were more effective against Gram-positive and Gram-negative bacteria than their controls. The modified resins were also significantly more effective against Candida albicans than controls, but no resin was effective against Aspergillus niger. The cell viability of cultures submitted to substances leached from the PDADMAC resins was similar to that of cells cultured under ideal conditions. The incorporation of PDADMAC into the acrylic resins achieved the desired antibacterial effect, with no changes in the biocompatibility properties of the resins. Moreover, the modified resins were effective against Candida albicans, the most common fungus in the oral cavity. Thus, the incorporation of PDADMAC in biomaterials seems to be promising in dentistry.

On the drying behavior of natural oils used for solid wood finishing

Drying oils provide exquisite bio-based finishes for wood products but their application is restricted by their time-consuming polymerization. Research and industrial development are impeded by a lack of scientific methods to follow the polymerization progress of oils applied on wood. We investigated the drying behavior of linseed oil, tung oil, and their 1:1 mixture both with and without the addition of a drier. Liquid samples revealed faster polymerization of the mainly conjugated and highly unsaturated tung oil than of non-conjugated linseed oil. Recurring water contact angle measurements of oil finishes applied on beech and oak wood showed clear differences in wetting. Tung oil provided hydrophobicity to all wood samples soon after its application, even when used without drier. Linseed oil required longer drying times and was more susceptible to substrate influences but ultimately reached the highest contact angles when equipped with a drier. Further, we observed a relationship between drying time and contact angle stability. As a new and straightforward tool to characterize the drying progress of applied oil-based finishes, we propose the calculation of a contact angle reduction factor, that takes into account both the initial water contact angle as well as its stability over measurement time.

The effect of magnetic field on stability of conventional and pickering water-in-crude oil emulsions stabilized with fumed silica and iron oxide nanoparticles

The injection of solid stabilized water-in-crude oil emulsion to displace heavy crude oil is a new EOR method. Although high emulsion stability, which is essential for achieving the maximum process efficiency, can be obtained using nanoparticles, developing an inexpensive and environmentally friendly technique that improves emulsion stability is highly beneficial to this method. Magnetic field and magnetized water technologies have such capabilities. Contact angle reduction on solid surfaces is among the modifications that occur in the properties of water due to the magnetization. Although studies show that using these technologies might be amenable for enhanced oil recovery, there has been no investigation into their use to alter conventional and solid stabilized water-in-crude oil emulsion stability. In this study, the magnetized water, prepared with distilled water, is used in the process of emulsion preparation and the resulting emulsion stability is compared to that prepared with normal water. Our findings show that using magnetized water improves the stability of solid stabilized emulsion made with fumed silica and iron oxide nanoparticles, while it does not impact the stability of conventional emulsions. Lower three-phase contact angle in case of using magnetized water compared to that of normal water implies that the hydrophobic nanoparticles more rigidly stick to the oil-water interface and more energy is required in order to detach them from the interface. This results in more stable solid stabilized emulsion. Results indicate that applying the magnetic field to a prepared conventional emulsion makes it a bit less stable. The reorientation of asphaltene molecules and resulting disturbance of the interface layer, along with the oil viscosity reduction, which accelerates the coalescence of dispersed water droplets, results in less stable emulsions. Although applying the magnetic field to the solid stabilized emulsion, prepared with fumed silica nanoparticles, has no effect on its stability, it significantly reduces the stability of the iron oxide nanoparticle stabilized emulsion. The magnetic force that exists between the magnets and the iron oxide nanoparticles, forcibly separates them from the interface and leads to emulsion breakage. The findings of this study could help in better understanding of the mechanisms involved in the stability of solid stabilized emulsions. Besides, a new field, in which the magnetized water can be successfully applied, is introduced.

The effect of selective mineralization of PLLA in simulated body fluid induced by ArF excimer laser irradiation: Tailored composites with potential in bone tissue engineering

In this paper we exposed samples of poly(l-lactide) (PLLA) extruded foil to ArF excimer laser (193 nm) radiation near the ablation threshold. The modified foil was immersed in the Simulated Body Fluid (SBF) at 37 °C for both short and long time (short term: up to 24 h, long term: up to four weeks). We described the physicochemical changes in PLLA before and after incubation in SBF. The laser irradiated PLLA incubated in SBF revealed turbidity on the irradiated surface. UV–Vis spectroscopy showed a remarkable decrease in transmittance for the irradiated PLLA incubated in SBF as compared to the non-irradiated PLLA incubated in SBF. Scanning electron microscopy proved the presence of minerals on the surface of PLLA in the laser irradiated area. The mineralization occurred only on the irradiated surface indicating that the process is selective. In the mineralized area a reduction of water contact angle was observed, suggesting a higher hydrophilicity of the surface. Moreover, a reduction in molecular weight was recorded in the long term incubation experiment for irradiated PLLA as compared to the unmodified sample. The samples were also investigated in terms of supramolecular changes in the material (DSC) and in terms of their thermal properties (TGA).

Application of Atmospheric Pressure Argon Plasma Jet (APAPJ) in Biomedical Science and Engineering

In this paper, we demonstrated the application of atmospheric pressure argon plasma jet (APAPJ) in biomedical science such as cancer therapy and biomedical engineering such as surface modification of polystyrene Petri dishes for animal cell culture. We observed that APAPJ, when exposed to breast cancer cell line (MDA-MB-231) for 60 seconds at a distance of ~ 2.5 cm, reduced the cancer cells by 57%. This reduction in cancer cell concentration demonstrated the cancer-killing property of APAPJ. Further optimization of APAPJ's various operational parameters and in-depth biochemical study is required to figure out the mechanism responsible for killing cancer cells. Also, we investigated cell adhesion and proliferation due to APAPJ treatment by Crystal Violet (CV) staining and MTT Assay. We observed that APAPJ treatment of polystyrene Petri dishes for 60 - 240 s at a distance of ~ 3.5 cm exhibited enhancement in adhesion of breast cancer cell line (MDA-MB-231). We also demonstrated the increase in hydrophilicity by a reduction in contact angle to 30.3°±3 after 240 seconds of APAPJ treatment of polystyrene samples. The hydrophilicity of the substrate has proven to enhance cell adhesion. Consequently, APAPJ could be employed as a simple, inexpensive and environmentally friendly method for surface modification of polystyrene plates for animal cell culture.

Experimental investigation of Alfalfa natural surfactant and synergistic effects of Ca2+, Mg2+, and SO42− ions for EOR applications: Interfacial tension optimization, wettability alteration and imbibition studies

Fractured moderate oil-wet carbonate reservoirs are the main productive formations in the Middle East. The change in wettability state toward water wetness beside interfacial tension (IFT) reduction is one of the potential scenarios for more oil recovery process. Smart water and natural surfactant injection into the porous media will alter the rock wettability and reduce IFT which consequently results in more oil sweep from untouched pores. In this paper, a novel natural surfactant (Alfalfa species) is introduced for EOR applications. IFT and contact angle tests were carried out between the oil phase, rock surface, Alfalfa natural surfactant, and surfactant—ion hybrid aqueous solutions. The results of Alfalfa natural surfactant showed a 29.29 mN/m reduction of IFT (63.39% IFT optimization) at the concentration of 4 wt% as the critical micelle concentration (CMC). Also, after addition of Alfalfa the wettability of rock tends to be more water-wet from the initial oil-wet state by application of Alfalfa because of 86.84° reduction of contact angle (49.91% wettability alteration). Solutions of calcium, magnesium, and sulfate ions were prepared as modified synthetic seawater at CMC of Alfalfa natural surfactant to investigate their synergistic influences on intensifying the optimizations of IFT and wettability alteration as hybrid solutions. IFT measurements of the hybrids demonstrated that among mentioned ions calcium brings the best results as it showed good synergistic effects with mentioned non-ionic natural surfactant in advancing the optimization of IFT reduction from 63.39 (surfactant solution) to 71.0 (surfactant—ion hybrid solution) percent. Also, contact angle measurements of the hybrids demonstrated that calcium ions gain the best results and advance the contact angle optimization from 49.91 (surfactant solution) to 61.8 (surfactant—ion hybrid solution) percent. Therefore, the solution of 3 times Ca concentrated seawater + CMC of surfactant selected to conduct imbibition tests as a displacement experiment based on the hybrid results and the candidate solution caused a 19.2% increase in oil recovery factor regarding seawater flooding and a total oil recovery factor of 62%.

Delignified bamboo as skeleton matrix for shape-stable phase change heat storage material with excellent reversible thermochromic response property

Abstract In this study, the porous bamboo material (DB) was obtained by removing the intercalated substance between the fibers through a simple delignification process, and was used as support matrix by impregnating a reversible thermochromic compound (BP: BPA: TD) to prepare a shape-stable bamboo-based composite reversible thermochromic phase change material (TBB-DB). Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis of bamboo and DB showed that lignin was removed from bamboo by the delignification process. The open porous structure founded in scanning electron microscopy micrographs allows the rapid impregnation of TBB to achieve reversible thermochromic and phase change storage properties. The reduction in surface roughness and contact angle leads to an increase in the hydrophilicity of the DB for the subsequent impregnation of the TBB into the porous structure of DB. DB also showed good mechanical properties and thermodynamic stability. The effects of different proportions of the color developer and the solvent in the compound TBB on the reversible thermochromic and phase change energy storage properties of TBB-DB were investigated. TBB-DB1:4:50 showed a better reversible thermochromic properties and energy storage properties (the highest latent heat, favorable melting and crystallization temperatures). As for TBB-DB1:4:50, the FTIR, XRD, thermal stability analysis showed that there is no chemical reaction occurred during the entire impregnation process, which is conductive to the reversible thermochromic phase change energy storage characteristics of TBB-DB1:4:50. The color of TBB-DB1:4:50 changed from rose red to white as the temperature increased. Compared with DB, TBB-DB1:4:50 showed endothermic and exothermic peaks, and its ΔHm and ΔHL+S were 113.5 J g−1 and 109.8 J g−1, respectively, indicating that TBB1:4:50 was well impregnated into DB to form a composite phase change material. TBB-DB1:4:50 also has good durability, making it able to withstand long-term recycling and maintain the original excellent performance.

Salinity-dependent alterations of static and dynamic contact angles in oil/brine/calcite systems: A molecular dynamics simulation study

In this study, classic Molecular Dynamics (MD) simulations with established force fields were first performed to investigate the salinity effects on the static contact angle of a n-decane droplet immersing in water atmosphere within a calcite nanochannel to advance our microscopic understanding on low salinity flooding. By applying an external body force, dynamic contact angle of n-decane in water phase was also studied in the presence of various salt concentrations based on Non-Equilibrium MD simulation. The predicted n-decane static contact angles are around 59.68° ± 0.26°, which agree well with experimental results in previous studies. A reduction of the static contact angle of the nanodrop is observed with the increase of salinity, which implies an enhancement of surface hydrophilicity. Under flow conditions, the deformation of nanodrop, as evidenced by the centre of mass analysis, becomes faster by increasing the salt concentration. The recovery/mobility of the n-decane nanodrop is, however, still significantly restricted by the adsorption interaction between the substrate and n-decane phase, which may lead to droplet snapping off and/or breaking up into small droplets.

Synergic Impacts of Two Non-ionic Natural Surfactants and Low Salinity Water on Interfacial Tension Reduction, Wettability Alteration and Oil Recovery: Experimental Study on Oil Wet Carbonate Core Samples

Low salinity water (LSW) flooding alters rock surface wettability toward more water wetness, and consequently, oil recovery will be increased from a carbonate oil reservoir. Surfactant flooding and polymer flooding enhance oil recovery by oil–water interfacial tension (IFT) reduction and water–oil mobility ratio change, respectively. In this study, a combination of LSW and two non-ionic natural surfactants for enhanced oil recovery was evaluated. Four types of salts (CaCl2, MgCl2, Na2SO4, and MgSO4) at different concentrations in distilled water were used to find optimal LSW based on contact angle (CA) reduction. Two non-ionic natural surfactants (a new natural surfactant from Gemini surfactants (GS) family and Tribulus terrestris surfactant) were applied to obtain their optimum concentration based on IFT reduction. The minimum IFT was achieved in 2000 ppm of GS (4.06 mN/m) and 3000 ppm of TTS (6.21 mN/m). Experimental results showed that the presence of GS in low salinity surfactant solution (1000 ppm of MgSO4 and 2000 ppm GS) is capable to reduce IFT (to 1.02 mN/m) and CA (to 31.25°). Therefore, GS showed good results in IFT improvement and wettability alteration. Finally, the optimal LSS was combined with different concentrations of PHPA polymer and injected into cores. Core flooding results demonstrated 69.7% oil recovery for LSW injection, 82.2% for low salinity GS injection (an increase of 12.5%) and 87.9% for low salinity GS-polymer injection (an increase of 5.7%).

Synthesis and characterization of water-soluble polyvinyl alcohol/pomegranate peel powder films

Biodegradable plastics had gained much attention among the researchers due to the arising of sustainability and environmental issues caused by petrochemical-based plastics. In this study, PVA films incorporated with pomegranate peel powder (PPP) were synthesized by using solution casting method. The effect of PPP on the surface morphology, physical properties, barrier properties and antibacterial activity of PVA based films were studied through FE-SEM, water solubility test, water contact angle test and Kirby-Bauer test. The incorporation of PPP had significantly enhanced the water solubility and surface energy of PVA-PPP films with the increasing of PPP content that caused reduction in water contact angle of the films. However, the films do not show a significant effect on the antibacterial efficacy against E.coli. In conclusion, PVA-PPP films have great potential to be used as green packaging materials for cosmetics products provided that further study on antibacterial efficacy against gram positive bacteria should be conducted.

Plasma Treatment Reduced the Discoloration of an Acrylic Coating on Hot-Oil Modified Wood Exposed to Natural Weathering

We test the hypothesis that plasma-treatment will remove oil from the surface of hot-oil modified blue-stained pine wood, and improve the adhesion and outdoor performance of a white acrylic coating on the modified wood. Modified wood was treated with water-vapour plasma, and microstructural changes at wood surfaces were examined. Plasma treatment removed oil from the surface of modified wood and etched bordered pits. The contact angle of water droplets on modified wood was 91.8°, but plasma-treatment for only 33 s reduced contact angle to less than that of the unmodified control (48.6°). The adhesion of the acrylic paint to modified wood was unaffected by plasma-treatment, but the adhesion rating of coated samples tested wet was slightly lower (3.1) than that of the coating on samples tested dry (3.5). The lightness value (CIE-L) of the acrylic coating on hot-oil modified wood samples exposed outdoors for 18 months was significantly lower (darker, 65.5) than that of the coating on similarly modified and exposed samples pre-treated with plasma (75.8). We conclude that plasma-treatment shows promise as a way of removing oil from the surface of hot-oil modified wood and reducing the discolouration of an acrylic coating on modified wood exposed to natural weathering.

Atomistic Molecular Dynamics Simulations of Surfactant-Induced Wettability Alteration in Crevices of Calcite Nanopores

Wettability alteration is an important mechanism in surfactant-facilitated enhanced oil recovery (EOR) in oil-wet carbonate reservoirs. An in-depth understanding of how surfactants influence the wettability of calcite surfaces is of crucial importance. In this study, atomistic molecular dynamics simulations were used to elucidate how the nonionic and anionic surfactants influence the wettability at the corners of angular calcite pores. A multicomponent oil model was constructed based on a chemical analysis of an unconventional reservoir crude oil. It was found that the inclusion of the calcite surface water layer caused a significant decrease in the attraction between the surface and the surfactant molecules from hundreds of kJ/mol to essentially zero. The surface water layer is therefore critical for an accurate description of calcite wettability. Simulated flooding of the oil-filled calcite pore with both types of surfactants was compared to that with blank brine. It was found that the tested surfactants alter the wettability of the calcite surface mainly by hydrophobic interactions with the adsorbed polar oil components and by weakening the interactions between polar and nonpolar oil components. The wettability alteration resulted in a 20–30° reduction in contact angles, while the ratio of the polar-to-nonpolar oil components within the pore decreased by approximately 50% by the surfactants as compared to just brine. The results presented in this work can provide guidance for selection of the most effective surfactants for oilfield applications.

Rapid degradation characteristics of an air‐cooled PEMFC stack

Durability is one of the obstacles to the large-scale commercialization of proton exchange membrane fuel cell (PEMFC) stacks. Understanding its decay behavior is a prerequisite for improving durability. In this study, rapid degradation characteristics of an air-cooled PEMFC stack are investigated. Due to the simultaneous presence of various degradation sources, the maximum power of the PEMFC stack has been reduced by 39.6% after just 74.6 h of operations. Performance degradation characteristics are sought by analyzing the cell voltage, temperature distribution, ion chromatography, and surface morphology of the gas diffusion layer. The result shows that abnormal cell voltage and temperature distribution can reflect the problematic location. The fluoride ion emission rate is 0.111 mg/day, which proves that the membrane has been seriously degraded. Contact angle reduction and impurities attached to the surface of the gas diffusion layer lead to the water management failure. It is also found that the main factor for performance degradation could be different under different current conditions. And more information can be found under higher current conditions during monitoring the decay of PEMFCs. This study helps to deepen the understanding of performance degradation characteristics.

Whey protein films added with galactooligosaccharide and xylooligosaccharide

This study aimed to evaluate the effect of addition of xylooligosaccharide (XOS) and galactooligosaccharide (GOS) to whey protein (WP) films produced by casting technique and using glycerol as a plasticizer. The films were evaluated for thickness, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties, water vapor permeability (WVP) and contact angle. No effect of the addition of prebiotic components on thickness of the films was observed (0.13–0.14 mm, p > 0.05). XOS and GOS addition resulted in similar cross-sectional SEM images, presenting smaller and retracted laminated structures, with lower tensile strength and higher elongation at break (3.8–1.7 MPa and 144–208%, respectively, p < 0.05); In addition, the XOS and GOS addition reduced the WVP (1.09–0.63 g.mm.h−1.m−2.kPa−1, p < 0.05), despite the higher hydrophobicity evidenced by contact angle reduction (56.61–46.69°, p < 0.05). Finally, thermal analysis indicated that the increased XOS and GOS concentration resulted in films with lower melting points (169.6–135.65 °C, p < 0.05). The possibility of using XOS and GOS to manufacture WP-films formulation provided interesting changes, creating new forms to combine and add value to biopolymers, considering technological and functional aspects.

Selective ozone treatment of PDMS printing stamps for selective Ag metallization: A new approach to improving resolution in patterned flexible/stretchable electronics

HypothesisSelective ozone treatment of Polydimethylsiloxane (PDMS) print-stamps may facilitate local de-wetting of Krytox®1506 oil; the resulting printed pattern can be used as a masking liquid during roll-to-roll vacuum-metallization, exemplified with Ag. This novel method may exploit high-throughput manufacture without chemical etchants or elevated temperatures for thin-film electronics. ExperimentsThe mechanism for selective wetting arose from O3 treatment of PDMS through a shadow-mask to vary surface-energy due to formation of polar silanol (Si-OH) replacing surface methyl groups leading to contact angle reduction from 40°-9° for oil on PDMS. Oiled PDMS was (1) metalized itself and (2) used as a stamp to print onto polyethylene-terephthalate, consisting of oil pick-up/de-wetting/transfer-to-substrate/metallization. FindingsAg (520–568 nm) thick was deposited outside oiled regions, surpassing ~20 μm resolution of commercial printing. On metalized PDMS, minimum line widths were 2.6 μm (with 10 μm edge-grading from centrifugal oil spreading) or widths of 24 μm (no Ag grading) following spin-coating/roll-coating oil respectively. The progressive effect of thinning oil via five successive stamp-to-substrate impressions, produced line widths of 14 μm (with graded edge of 7.6 μm via spreading from stamp-substrate compression). Developments may reduce reliance on laser engraving/photocuring, and could enhance micro-contact printing through liquid dynamics vs. topographical relief structures.

Time-dependent wettability changes on plasma-treated surfaces of unmodified and thermally modified European beech wood

The wettability of a freshly cut wood surface will change over time, which is denoted as natural ageing. Water contact angle measurements indicated that the thermal modification of European beech reduces its wettability, but does not affect the rate at which the contact angle increases within a 4-week period. A plasma treatment of fresh wood surfaces enhanced the wettability and equaled the wettability properties of unmodified and thermally modified wood surfaces. The contact angle on plasma-treated wood surfaces increased faster than on unmodified wood surfaces, but a reduction in contact angle by the plasma treatment was still evident after ageing for 4 weeks.

Anti-frosting performance of sprayable superhydrophobic coating suitable for outdoor coil of air source heat pump

Spraying method to prepare superhydrophobic surface is more efficient than the wet chemical etching used before, and is more suitable for outdoor coil of air source heat pump. However, durability in frosting/defrosting cycles and anti-frosting performance should be clarified before applying the sprayable superhydrophobic coating to solve the frosting problem. Superhydrophobic surface was prepared in this paper, by spraying SiO2 coating on aluminum surface. Frosting and defrosting tests were carried out to verify its durability and anti-frosting performance. The self-jumping of condensate droplets were focused on at early stage of frosting. Moreover, a theoretical model was developed to analyze the influence of the superhydrophobic surface characteristics on self-jumping of condensate droplets. The durability of the sprayable surface was greatly improved compared with the etched surface. Continuous self-jumping of condensate droplets was achieved at early stage of frosting, and theoretical analysis indicated that reducing contact angle hysteresis was the key to achieve self-jumping. Compared with the surface having equal contact angle but larger angle hysteresis, self-jumping reduced the surface coverage of droplets on the sprayable surface, as a result, decreasing the frost layer thickness by 33% after frosting for 60 min, which indicated that the sprayable surface had excellent anti-frosting performance.

Wettability alteration and oil recovery by spontaneous imbibition of smart water and surfactants into carbonates

Naturally fractured carbonate reservoirs have very low oil recovery efficiency owing to their wettability and tightness of matrix. However, smart water can enhance oil recovery by changing the wettability of the carbonate rock surface from oil-wet to water-wet, and the addition of surfactants can also change surface wettability. In the present study, the effects of a solution of modified seawater with some surfactants, namely C12TAB, SDS, and TritonX-100 (TX-100), on the wettability of carbonate rock were investigated through contact angle measurements. Oil recovery was studied using spontaneous imbibition tests at 25, 70, and 90 °C, followed by thermal gravity analysis to measure the amount of adsorbed material on the carbonate surface. The results indicated that Ca2+, Mg2+, and SO42− ions may alter the carbonate rock wettability from oil-wet to water-wet, with further water wettability obtained at higher concentrations of the ions in modified seawater. Removal of NaCl from the imbibing fluid resulted in a reduced contact angle and significantly enhanced oil recovery. Low oil recoveries were obtained with modified seawater at 25 and 70 °C, but once the temperature was increased to 90 °C, the oil recovery in the spontaneous imbibition experiment increased dramatically. Application of smart water with C12TAB surfactant at 0.1 wt% changed the contact angle from 161° to 52° and enhanced oil recovery to 72%, while the presence of the anionic surfactant SDS at 0.1 wt% in the smart water increased oil recovery to 64.5%. The TGA analysis results indicated that the adsorbed materials on the carbonate surface were minimal for the solution containing seawater with C12TAB at 0.1 wt% (SW + CTAB (0.1 wt%)). Based on the experimental results, a mechanism was proposed for wettability alteration of carbonate rocks using smart water with SDS and C12TAB surfactants.

Morphology and Physicochemical Properties of Branched Polyurethane/Biopolymer Blends.

The aim of this study is the analyze the structure of branched polyurethanes based on synthetic poly([R,S]-3-hydroxybutyrate) and their blends with biopolymers and montmorillonite. The properties which would predict the potential susceptibility of these materials to degradation are also estimated. Fourier-transform infrared spectroscopy with attenuated total reflection analysis shows that poly([d,l]-lactide) is on the surfaces of polyurethanes, whereas chitosan and starch are included inside the blend network. Atomic force microscopy images have shown that the surfaces of investigated samples are heterogenous with the formation of spherulites in case of pure polyurethanes. The presence of biopolymers in the blend reduced the crystallinity of polyurethanes. Thermal stability of blends of polyurethanes with poly([d,l]-lactide) and polysaccharides decreased in comparison to pure polyurethanes. Although the tensile strength is reduced after the blending of polyurethanes with biopolymers, the elongation at break increased, especially in the case of polyurethane/poly([d,l]-lactide) blends. The presence of polysaccharides in the obtained blends caused the significant reduction of contact angle after one minute from water drop immersion. This hydrophilizing effect is the highest when montmorillonite has been incorporated into the chitosan blend. The estimated properties of the obtained materials suggest their potential sensitivity on environmental conditions.