Dynamic Contact Angle Analysis Research Articles

Halogen‐free boron‐based hybrid system for enhancing flame retardancy, mechanical and thermal properties of epoxy

AbstractThis study aims to increase the flame retardancy of epoxy‐based composites by using various flame retardants together with colemanite filler (CLM), which is a very mineral‐rich boron type. As a flame retardant, aluminum hydroxide (Al(OH)3) and boron‐containing compounds: borax (BRX) and natural minerals (tincal (TNC) and colemanite (CLM)), as well as barium metaborate (BaMB) synthesized by us were used. Scanning electron microscopy (SEM), x‐ray powder diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), contact angle (CA), and particle size analysis were used to characterize the composites and additives. All boron compounds increased the thermal stability of the composites. Except for the ER/CLM‐BaMB composite, other composites' surface contact angles were over 90°. In terms of both combustion and thermal properties, the best CLM‐BaMB‐Al(OH)3‐TNC ratio was determined as 15:5:15:15. The tensile strength, self‐extinguishing time, estimated and experimental Limited Oxygen Index (LOI) values for this composite were determined as 96 MPa, 65 s, 29.6%, and 25%, respectively. In addition, ANOVA was applied to determine the effect of hybrid filler type and different weight ratios on the mechanical properties of composites.

Effect of sizing agents on tensile properties of carbon fiber filament wound structures

In order to evaluate the effects of sizing agents on the wettability, strength loss, and properties of final filament wound structures during filament winding of carbon fibers, three types of sizing agent based on epoxy, epoxy + polyester, and epoxy + polyurethane were used to treat carbon fibers, the surface properties of carbon fiber samples after treatment were evaluated using SEM, infrared spectroscopy, dynamic contact angle analysis, and interlaminar shear strength (ILSS) test, the strength loss caused by fiber damage during filament winding was quantitatively analyzed, and the strength properties of the filament wound structures were characterized by NOL ring test. The results showed that the sizing agent treatment only slightly improved the surface free energy and ILSS of carbon fibers, but it had obvious influence on the strength loss rate of carbon fiber bundles. Added polyester or polyurethane in epoxy-based sizing may improve its protective effect for carbon fiber, and thus decrease strength loss during winding process, result in better tensile properties of carbon fiber filament wound structures.

Impact of hybrid surfaces on the droplet breakup dynamics in microgravity slug flow: A dynamic contact angle analysis

Microfluidic devices, which enable precise control and manipulation of fluids at the microscale, have revolutionized various fields, including chemical synthesis and space technology. A comprehensive understanding of fluid behavior under diverse conditions, particularly in microgravity, is essential for optimizing the design and performance of these devices. This paper aims to investigate the effects of discontinuous wettability on droplet breakup structures under microgravity conditions using a microchannel wall. The approach we adopt is underpinned by the volume-of-fluid methodology, an efficient technique renowned for its accurate resolution of the fluid interface in a two-phase flow. Furthermore, a modified dynamic contact angle model is employed to precisely predict the shape of the droplet interface at and near the wall. Our comprehensive model considers influential parameters such as slug length and droplet generation frequency, thereby providing crucial insights into their impact on the two-phase interface velocity. Validated against existing literature data, our model explores the impact of various configurations of discontinuous wettability on breakup morphology. Our findings highlight the significance of employing a dynamic contact angle methodology for making accurate predictions of droplet shape, which is influenced by the wall contact angle. Emphasis is placed particularly on the effects of slug length and droplet generation frequency. Notably, we demonstrate that the use of a hybrid surface at the junction section allows for precise control over the shape and size of the daughter droplets, contrasting with the symmetrical division observed on uniformly hydrophilic or superhydrophobic surfaces. This study contributes valuable insights into the complex dynamics of the droplet breakup process, which has profound implications for the design and optimization of microfluidic devices operating under microgravity conditions. Such insights are further poised to augment applications in space exploration, microreactors, and more.

Hydrophobization of Inorganic Oxide Surfaces via Ring-Opening Polymerization of Cyclic Siloxane Vapor.

The ability to control the surface chemistry of inorganic oxides has a profound impact on numerous applications, including lubrication, antifouling, and anticorrosion. While often overlooked as potential modifying agents given their lack of traditional functional groups, siloxanes have recently been shown to react readily with and covalently attach to inorganic oxide surfaces. Herein, we examine the reactions of cyclic siloxane vapor with solid interfaces via a ring-opening polymerization (ROP) initiated by the inherent acid/base characteristics of several smooth inorganic oxide surfaces. Surfaces are characterized by ellipsometry, dynamic contact angle analysis, and X-ray photoelectron spectroscopy (XPS). This technique requires no additional solvents and very little reactant to produce nanometer-thick hydrophobic surfaces that exhibit low contact angle hysteresis. Additional studies with particulate surfaces suggest that this method prepares conformal coatings regardless of surface architecture.

Hydroxyapatite/TPU/PLA nanocomposites: Morphological, dynamic-mechanical, and thermal study

Abstract Nanocomposites based on thermoplastic polyurethane (TPU) and poly lactic acid (PLA) with different weight ratios of 10:90 and 30:70 were prepared by solution method. Hydroxyapatite nanoparticles (n-HA) were used to enhance the physical and mechanical properties of the alloys. To prepare the nanocomposites, the percentages of n-HA varied between 1% and 5%. Different tests were used to investigate the properties of these nanocomposites. Scanning electron microscopy (SEM) analysis, which was used to study the morphology of the blends, showed that there were rough morphologies in between materials, and the results of the mapping test showed that the dispersion of nanoparticles in the polymer matrix was almost good. TGA thermal degradation test showed that the presence of TPU to some extent can affect the thermal stability properties, and with the increase in this material, the thermal properties are strengthened. The crystalline behavior of the samples showed that the presence of TPU and n-HA nanoparticles had negative effects on the crystalline properties. The study of viscoelastic behaviors showed that the presence of TPU enhances the viscous behavior in the sample and decreases the glass transition temperature, while the presence of nanoparticles increases the elastic properties and glass transition temperature. Tensile test showed that the presence of n-HA has a greater effect on the mechanical properties. Dynamic contact angle analysis using water and dimethylformamide (DMF) solvent showed that the existing TPU and n-HA led to major changes in the interaction surface of scaffolds. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis showed that increasing the amounts of TPU and HA increases cell viability. SEM cell interactions analysis showed that the surfaces of PLA90TPU10H5 and PLA70TPU30H5 samples are very good for the preparation of bone tissue scaffolds. Our findings indicated that the addition of n-HA into PLA/TPU blends could impart new features to the PLA matrix as a promising candidate for bone, cartilage, and tendon tissue engineering.

Construction of rough and porous surface of hydrophobic PTFE powder-embedded PVDF hollow fiber composite membrane for accelerated water mass transfer of membrane distillation

The construction of rough and porous hydrophobic membrane surface is expected to overcome the obstacles including low permeate water flux and membrane pore wetting which greatly restrict the development of membrane distillation (MD) technology. In this study, a rough and porous polytetrafluoroethylene (PTFE) powder-embedded polyvinylidene fluoride (PVDF) hydrophobic coating layer was compounded on the outer surface of PVDF hollow fiber support membrane by the dilute solution coating-phase inversion method. PVDF hollow fiber support membrane was fabricated by the dry-jet wet-spinning technique. PTFE powder was directly incorporated in PVDF dilute coating solution and embedded in the porous PVDF coating layer after the nonsolvent induced phase separation (NIPS). The variations of membrane morphology, surface chemical compositions, hydrophobicity and wetting resistance were investigated by scanning electron microscope (SEM), Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), dynamic water contact angle (WCA) and liquid entry pressure (LEP) analysis. Membrane separation performance including desalination and ionic dyes removal properties was evaluated by VMD experiment. Compared with PVDF hollow fiber support membrane, both the surface hydrophobicity and the water permeability of the PTFE powder-embedded PVDF hollow fiber composite membrane (HFC) had obvious improvement. The surface WCA and permeate water flux increased from 92.6° and 11.3 kg/m2.h for PVDF support membrane to 133.6° and 26.8 kg/m2.h for the PTFE powder-embedded HFC membrane meanwhile NaCl rejection can be maintained above 99.9% (3.5 wt% NaCl aqueous solution at 50 °C and permeate pressure at 31.3 kPa). The separation performance of HFC membrane can remain stable without obvious pore wetting during the continuous MD operation for 36 h. Different from the desalination, porous hollow fiber membrane would adsorb two different charged dyes, Congo red (CR) and methylene blue (MB) to a certain extent, resulting in the decrease of membrane flux and the change of permeate water quality. Finally, the MD separation mechanism of inorganic salt, anionic dye and cationic dye by PTFE powder-embedded HFC membrane was proposed.

Polymeric number average molecular weight in submicron films as a tool for the manipulation of water phenomena in translucent coatings

Absorption and desorption properties of poly(ethylene glycol) diacrylate (PEGDA) have seen to greatly vary depending on the molecular weight of the polymer, suggesting a dependence of the wetting phenomena on its molecular weight. Here, two sets of polymeric submicron films (140 and 190 nm) were fabricated by free radical polymerization using Phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide as the photoinitiator, and PEGDA (Mn 250 or 575). The films were spin coated on glass substrates to study their wetting phenomena by dynamic contact angle analysis. All films were characterized in terms of their thickness and transmittance. PEGDA Mn 250 films (Film-250) decreased the sliding time of water drops when compared to a clean glass substrate because of a decrement in the liquid-solid interface area. Nonetheless, when using PEGDA Mn 575 films (Film-575), an improvement in the adhesion forces between the coating and the drop of water was observed, avoiding the drop to slide down the substrate and leading to its later evaporation. In addition, Film-575 drastically changed their morphology after water exposure, while Film-250 remained the same. These characteristics are of special interest in environments where a response towards small amounts of water is desired, or where water evaporation is craved. Copyright © 2018 VBRI Press.

Comparative Evaluation of the Penetration Depth into Dentinal Tubules of Three Endodontic Irrigants.

This study aimed to examine the penetration depth into dentinal tubules of some chelating agents. The 17% EDTA and two preparations containing surfactants (Smear Clear, Bioakt Endo) were tested. Surface tension and liquid viscosity were measured using a Dynamic Contact Angle Analyzer and a Haake rotational rheometer. To measure the penetration depth inside dentinal tubules, thirty maxillary central incisors were selected from a pool of extracted human permanent teeth and allocated to three experimental groups (10 samples each), as well as were mechanically shaped and cleansed with 5.25% NaOCl, followed by each of the chelators being labeled with 0.1 wt % Rhodamine B according to final irrigation protocol established. The samples were embedded in an epoxy resin, after which 200 μm thick transverse sections were obtained at 2, 5, and 8 mm from the apex with a saw microtome. The specimens were then observed using a confocal laser microscope (CLSM) and the penetration of the labeled solution was measured in every third of each sample. Statistical analysis was performed using ANOVA or Kruskal–Wallis tests according to the distribution of data, evaluated with the Shapiro–Wilk normality test. Viscosity and surface tension tests have shown that BioAKT Endo has the lowest values compared to EDTA and Smear Clear. The medium penetration depth did not significantly differ among the three irrigants, while it increased considerably from the apical to the coronal level in all groups. Additionally, the maximum penetration depth increased significantly from the apical to coronal level, while among groups, BioAKT Endo showed the highest values at the apical and middle level compared to the other irrigants. No significant differences were observed among the three groups in medium and maximum penetration depths when the entire root was considered. New irrigants containing surfactants show reduced surface tension and, in one case (BioAKT Endo), viscosity. The lowering of the surface tension allows for better penetration of liquids into dentinal tubules than EDTA alone, thus improving the cleaning of the root canal system.

Tubular PAN/CNC thin film nanocomposite (TFN) pressure retarded osmosis (PRO) membrane: fabrication and preliminary evaluation in desalination process

The pressure retarded osmosis (PRO) process requires high performance, high flux, high rejection, and resistant membranes under harsh conditions. Since conventional phase-inversion membranes are insufficient to permit the required water flux, alternative membrane fabrication methods need to be developed. Many studies have recently been carried out to fabricate strong enough nanofiber PRO membranes resistant to higher pressure while providing high flux and high rejection rates. This work aims to fabricate tubular nanofiber PRO membranes by the electrospinning technique. In the study, cellulose nanocrystals (CNCs) were added to polyacrylonitrile (PAN) polymer solution to fabricate nanocomposite nanofiber PRO membranes. According to the scanning electron microscopy (SEM), FT-IR, dynamic mechanical analysis, porometer, and contact angle analysis results, it is concluded that PAN and CNCs provided a complete mixture, and the addition of CNCs increased the mechanical strength in the PAN membranes, which is the crucial phenomena in PRO applications. In this study, the newly fabricated membrane achieves a higher PRO water flux of 405.38 LMH using 1 M NaCl and a DI as feed water. The corresponding salt flux is found as 2.10 gMH, which is higher than our previous study. The selectivity of the reversed flux represented by the ratio of the water flux to the reversed salt flux (Jw/Js) was able to be kept as high as 193.03 L/g for PRO operation. As far as we know, the performance of the work-developed membrane in this study has shown better performance than all PRO membranes reported in the literature previously.Graphic abstract

Wetting mechanism and interfacial bonding performance of bamboo fiber reinforced epoxy resin composites

A polyacrylate-based wetting agent, BYK-358N, was used to improve the interfacial bonding between the bamboo fibers and epoxy matrix. Fourier transform infrared spectrometer and differential scanning calorimetry were used to study the curing process of epoxy resin. The wettability of the treated bamboo fiber, which by the untreated and wetting agent treated epoxy, was studied using the surface tension of epoxy and bamboo fiber. The analysis of dynamic contact angle and interfacial shear stress confirmed that the composite interface was improved. Finally, Vacuum-assisted resin transfer molding was used to prepare bamboo fiber reinforced epoxy resin (BF/EP) composites, and the tensile properties were measured. The results showed that the addition of the wetting agent could effectively improve the interface compatibility of BF/EP composites. The interfacial shear stress of BF/EP composites treated with 1% wetting agent was 24.36 MPa, tensile strength was 111.54 MPa, and Young's modulus was 3.90 GPa, which was 165.7%, 99.7%, and 66.7% higher than that of untreated BF/EP composites.

Preparation and characterisation of graphene oxide-enhanced poly (m-phenylene isophthalamide) ultrafiltration membrane with excellent alkali resistance

Membrane fouling is a challenge for the development of ultrafiltration (UF) membranes. Synergistic alkaline cleaning and membrane material modification is a promising membrane fouling control method. Poly(m-phenylene isophthalamide) (PMIA)/graphene oxide (GO) UF blend membranes with different GO contents were prepared via non-solvent–induced phase separation. The structure, filtration properties, and alkali resistance performance of the PMIA/GO membranes were different from those of PMIA membranes because GO contains several polar oxygen-containing functional groups. Scanning electronic microscopy (SEM) images revealed that the prepared PMIA/GO membranes presented large and tunnel-like microvoids which conferred excellent water permeability. X-ray photoelectron spectroscopy (XPS) analysis indicated that GO was successfully incorporated in the membranes and remained in the membranes after cleaning. The dynamic contact angle (DCA) analysis results demonstrated that the PMIA/GO membranes possessed remarkable hydrophilicity. Moreover, the separation performance of all membranes for bovine serum albumin (BSA) exceeded 93.50%, and the PMIA/GO-2 membrane with a GO content of 0.1 wt% presented the best reversible and irreversible anti-fouling capability of all prepared membranes. The as-prepared UF membranes can be used for protein contamination treatment, particularly for ovalbumin (OVA) separation, and can be used under alkaline conditions. Moreover, the membranes could be reused. The alkali resistance of the membranes was systematically evaluated and its mechanism was analysed in detail, and PMIA was confirmed as a promising UF membrane material.

Comparative studies of nitrogen plasma and argon plasma treatment on the strength of PBO fibre reinforced high-temperature resistant thermoplastic composite

The study involves the processing of a novel poly [1, 4-phenylene-cis-benzobisoxazole] (PBO) fibre reinforced high-temperature thermoplastic composite with polyaryletherketone (PAEK) as the matrix. The PBO fibre and the PAEK film surface was modified using the method of argon and nitrogen plasma treatment. The investigation primarily focuses on evaluating the tensile properties of the fabricated laminates and correlating it with the effect of plasma treatment, surface characteristics, and its fracture surface. A 5% decrease in tensile strength was observed post argon plasma treatment while a 27% increase in strength was observed post nitrogen plasma treatment. The morphology of the failure surface was investigated by scanning electron microscopy and an interfacial failure was observed. Furthermore, the effect of plasma on the wettability of PBO fibres and PAEK film surface was confirmed by the Dynamic Contact Angle analysis and sessile drop method respectively. FTIR spectral analysis was done to investigate the effect of plasma treatment on the chemical structure on the surface. The results of the wettability study showed that the argon plasma treatment of the fibre surface increased its hydrophobicity while nitrogen plasma treatment resulted in the reduction of contact angle.

Influence of surface modification of carbon fiber based on magnetron sputtering technology on mechanical properties of carbon fiber composites

To improve the interfacial performance of carbon fiber (CF) and epoxy resin, the surface of CF was modified using magnetron sputtering technology, and a CF epoxy resin (CFER) composite was prepared using injection molding technology. The influence of magnetron sputtering technology on the surface properties of CF was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamic contact angle analysis (DCAA). The influence of the surface modification of the CFs by magnetron sputtering on the mechanical and interfacial properties of CF composites was analyzed by testing the tensile and bending properties of the CFER composites. The results indicated that the surface morphology of CF can be modified by magnetron sputtering, and a nano sized carbon film was deposited on the surface of the CFs. The morphology of the carbon film on the surface of the CFs was different from that on the silicon pellet. The surface roughness of the CF increased after it was modified by magnetron sputtering. The surface wettability of the CFs may be improved by increasing the surface free energy of the fiber owing to the deposition of the carbon film. Tests of the tensile and bending properties of the CFER composites showed that the surface modification of CFs by magnetron sputtering can effectively improve the mechanical properties of the CFER composites, which not only improves the tensile strength and bending strength, but also increases the tensile modulus and bending modulus. The SEM images showed that the interfacial adhesion between the modified CF and the epoxy resin was significantly improved. The stress–strain curves showed that the failure mode of the CFER composite modified by magnetron sputtering CF surface changed, and a stress yield phenomenon was observed.

Nano-Hydroxyapatite Airborne-Particle Abrasion System as an Alternative Surface Treatment Method on Intraorally Contaminated Titanium Discs.

The aim of this study was to test the nano-hydroxyapatite powder decontamination method on intraorally contaminated titanium discs and to compare this method with current decontamination methods in the treatment of peri-implantitis. Contaminated discs were assigned to six treatment groups (n = 10 each): titanium hand curette; ultrasonic scaler with a plastic tip (appropriate for titanium); ultrasonic scaler with a plastic tip (appropriate for titanium) + H2O2; short-term airflow system (nano-hydroxyapatite airborne-particle abrasion for 30 seconds); long-term airflow system (nano-hydroxyapatite airborne-particle abrasion for 120 seconds); Er:YAG laser (120 mJ/pulse at 10 Hz). There were also two control groups (n = 10 each): contaminated disc (negative control) and sterile disc (positive control). Scanning electron microscopy, energy-dispersive x-ray spectroscopy, and dynamic contact angle analysis were used to determine the most effective surface-treatment method. The highest percentage of carbon (C) atoms was observed in the negative control group, and the lowest percentage of C atoms was found in the long-term airflow group, followed by the short-term airflow, laser, ultrasonic + H2O2, ultrasonic, and mechanical groups. When the groups were examined for wettability, the lowest contact angle degree was observed in the long-term airflow, short-term airflow, and laser groups. Nano-hydroxyapatite and laser treatments for detoxifying and improving infected titanium surfaces may show the most suitable results for reosseointegration.

Development of high-permeable PSf/PANI-PAMPSA composite membranes with superior rejection performance

Polysulfone is the most popular polymeric matrix material for fabrication of ultrafiltration membrane but suffers from its hydrophobic nature that caused low flux and fouling problems that limits its development and industrial applications. The blending PSf with hydrophilic polymers is an attractive and effective technique to improve the hydrophilicity of membrane. Here poly(2-acrylamido-2-methyl-1-propane sulfonic acid doped polyaniline was synthesized and used as a hydrophilic additive in polysulfone to obtain ultrafiltration range membranes with higher flux. Infrared results supported the increased hydrophilicity of the membranes with PANI-PAMPSA additive which is confirmed by dynamic contact angle analysis results as well. The cross-sectional SEM images revealed that the pristine and blend membranes were asymmetric structured and had dense skin layer, finger-like pores on the top and sponge-like pores underneath the porous support layer. Also, the skin layer of the membrane became thinner and denser with the addition of 0.1 and 0.25 % and thicker with the addition of 0.5 additive ratio. The initial contact angles of P0, P1, P2 and P3 measured as 85, 81, 79 and 72°, respectively. Pure water permeability of the P0, P1, P2 and P3 membranes calculated as 14.0, 17.2, 23.4 and 21.3 L.m−2. h−1. bar−1, respectively. The rejection ratios of the prepared membranes increased from 90.1 (P0) to 95.8 and 98.4 % for P1 and P2 membranes then decreased to 95.2 % for P3 membrane. The rejection results indicated that the prepared membranes can be classified as ultrafiltration membranes with molecular weight cut-offs (MWCOs) lower than 66 kDa g mol−1.

Effect of wettability on the water entry problem of aluminum spheres

We investigated the hydrodynamics of water entry by aluminum spheres varying in wettability, assisted by nano/microscaled surface morphology. A wide range of contact angle (C.A.: 0° ≤ θ0 < 170°) on the test spheres was prepared via inexpensive single-step anodization method. The water entry events: Splash and cavity formation, were visualized by a high-speed camera to understand the fast transient features affected by the surface wettability. In terms of hydrodynamics, cavity formation and air entrainment during the water entry were analyzed via dynamic wetting of liquid film flow along the sphere surface. It was confirmed that wettability was a determinant factor of both splash shape and cavity formation, especially in hydrophobic condition (90° ≤ θ0). Furthermore, the analysis of dynamic contact angle of liquid film front in this study was able to classify the water entry events more detail than previous literature. In addition, we also recorded audio signals to evaluate acoustic pressures produced by the impact between spheres and water pool. The audio signals, which are expected to be proportional to acoustic pressures, differed when hydrophilic and hydrophobic spheres entered water.

Root dentin surface activation to improve bioceramic bonding: Ascanning electron microscopic study

Background. Bioceramics need to interact chemically with dentin to exhibit adequate bioactivity. Proper bonding of bioceramics with dentin is of considerable importance. This study aimed to evaluate the wettability and marginal adaptation of bioceramics after the use of surface-active agents on dentin: %0.5 cetrimide and %1 alkylbenzene sulfonate. Methods. Of ninety maxillary central incisors, 45 teeth were sectioned longitudinally with 45 root halves randomly assigned to three groups (n=15): group I: no pre-treatment; group II: %0.5 cetrimide; group III: %1 alkylbenzene sulfonate. Then, the samples were subdivided into three subgroups (n=5): subgroup I: MTA; subgroup II: Biodentine, and subgroup III: BioRoot. A controlled-volume droplet of bioceramic material was placed on each root half, which was positioned in a dynamic contact angle analyzer to record the static contact angle for wettability. The remaining 45 samples were decoronated; the root canals were prepared and randomly categorized, as mentioned above. The root canal surfaces were treated, filled with the bioceramic material, transversely sectioned, and then each middle section was analyzed microscopically for marginal adaptation. Statistical tests used included post hoc Tukey tests and one-way ANOVA. The level of statistical significance set at %95 (P<0.05). Results. The contact angle values and interfacial gap width values after surface pre-treatment were significantly lower when compared to no pre-treatment group (P<0.05). The values were significant for %0.5 cetrimide in the case of Biodentine and %1 alkylbenzene sulfonate in the case of BioRoot (P<0.05). Conclusion. The two surfactants yielded promising results for enhancing the wettability and marginal adaptation of materials to the root dentin, which is required for obtaining an adequate seal, penetration, and bond strength of bioceramics.

Chlorination Treatment of Meta-Aramid Fibrids and Its Effects on Mechanical Properties of Polytetramethylene Ether Glycol/Toluene Diisocyanate (PTMEG/TDI)-Based Polyurethane Composites.

Meta-aramid fibrids (MAF) have attracted much attention. However, it is difficult for this high mechanical performance fiber to form sufficient interface adhesion between the MAF and polyurethane (PU) matrix due to the chemical inertness of its surface. Thus, the surface activity of MAF should be improved to obtain a high-performance MAF/PU composite. A novel methodology to modify the surface of MAF with a sodium dichloroisocyanurate solution (DCCNa) was developed to obtain chlorinated MAF (MAFC) in this study. A series of MAFC/PU composites was prepared by in situ polymerization processes. The results of Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) demonstrated that the chlorine-contained chemical groups were introduced onto the MAF surfaces after chlorination. Dynamic contact angle analysis (DCAA) revealed that the surface wettability and the surface free energy of the MAFC were significantly improved, which allowed for strong chemical bonding to PU. Scanning electron microscopy (SEM) showed a uniform distribution of MAFC and good interfacing bonding between the MAFC and PU. With the incorporation of 1.5 wt% MAFC into the polyurethane matrix, the tensile and tear strength values of MAFC/PU were 36.4 MPa and 80.1 kN·m−1 respectively, corresponding to improvements of approximately 43.3% and 21.1%, as compared to those of virgin PU as 25.4 MPa and 66.1 kN·m−1, respectively.

Compare numerical modeling and improved understanding of dynamic sessile drop contact angle analysis in Liquid-Solid-Gas system

Dynamic contact angle measurement; as a standard method for surface wettability analysis, is usually conducted through the analysis of sessile drops formed following the low rate injection of fluid from beneath through a drilled hole via an injection needle. However, understanding/characterizing the changes of drop contact angle from the point where the flat solid surface begins is not well discussed yet. Moreover, during the evaluation of size-dependent behavior of contact angle of millimeter-scale drops, the effect of the drilled hole is ignored. In this regard, in the current study, the experimental and thermodynamic characterizations of the sessile drop advancing contact angle measurements for a liquid-solid-air system are presented. To do this, a set of dynamic contact angle experiments for a water-calcite-air system with different devised hole diameters and roughness is conducted, and Gibbs free energy analysis is then utilized to propose a modeling scheme. Experimental results revealed a transient region from zero infinite contact angle at the hole to infinite contact angle of the solid surface, which was equal to 74.61° and 69.05° for nanoscale, and microscale surface roughness. In addition, it was shown that with a decrease in the hole diameter, the transient region met a lower value of contact angle at different dimensionless volumes. The result of higher advancing contact angle measured for the system with smaller drilled hole diameter was attributed to higher contact-line velocity. However, the assumption of low rate advancing contact angle was not violated for the hole diameter larger than 1.4 mm. Numerical studies demonstrated that in the case of zero line tension, two straight lines with positive slop could be fitted to the data; attributed to drilled hole effect. Besides, it was concluded that this behavior should not be interpreted as a negative line tension effect. The obtained values of line tension and equilibrium advancing contact angle, as matching parameters, were in agreement with those reported in the previous studies. Results of this work could help for better analyzing the size-dependent behavior of millimeter-scale drop through a suggested size-dependent model.

Investigation on electrical tuneable separation properties for phase inversion polyaniline membranes doped in various acids

Electrically tuneable polyaniline (PANI) membranes were fabricated via phase inversion and were doped primarily in various acids namely anthraquinone sulfonic acid (ASA), dodecylbenzene sulfonic acid (DBSA), maleic acid (MA) and poly(methyl vinyl ether-alt-maleic acid) (PMVEA) in comparison with secondarily HCl-doped PANI membrane as the pristine ones. It was found that the addition of different dopants in the PANI matrix changed the thickness of the membrane skin structure. From the dynamic contact angle (DCA) analysis, the PANI-ASA and pristine PANI membranes had the greatest permeation tuneability with a faster permeation rate under electric potential. For the effect of tuneable filtration, by using a modified cross-flow membrane filtration system, ASA showed the highest flux tuneability with a tuneable MWCO in the low UF range at an applied voltage of 7 V rather than at 0 V. Accordingly, the electrical tuneability assessment of the membranes has successfully demonstrated the proof of concept that the fabricated PANI membranes doped at various acids could have a different tuneable MWCO, selectivity and/or flux in a pressure filtration system.