Liquid Adhesion Research Articles

Dielectric barrier discharge (DBD) plasma pretreatment of lignocellulosic materials in air at atmospheric pressure for their improved wettability: a literature review

AbstractThe treatment of wood surfaces with gas discharges is one of the methods to achieve better surface adhesion properties. Good penetration, spreading and wettability of the applied liquid adhesives and coatings is a crucial factor for their adequate mechanical properties. Plasmas are the result of electrical discharge and can be created in different ways. The plasma treatment (PT) is frequently executed prior to material bonding or coating via the so-called dielectric barrier discharges (DBD) at atmospheric pressure. This literature review summarizes the essential aspects of DBD PTs aiming at a better wettability and surface adhesion. After introduction of the principle of DBD, the individual effects of internal and external parameters of the process will be discussed, which influence the final properties of treated materials.

Effect of nanoparticles concentration on the characteristics of nanofluid sprays for cooling applications

This study addresses the effect of nanofluid synthesis on the rheological properties of the resulting fluid and their consequent effect on the characteristics (size and velocity distribution of droplets, spray cone angle, etc.) of the sprayed nanofluids. The results are discussed in the light of how the spray characteristics affect the use of the resulting nanofluid spray for cooling purposes. Nanoparticles of alumina (Al2O3) and zinc oxide (ZnO) are mixed in water-based solutions, for concentrations varying between 0.5% and 2 mass% for alumina and between 0.01% and 0.1 mass% for the zinc oxide particles. FeCl2·4H2O (0.1 mass%) was also used to infer on the effect of the nature (material) of the particles in the physicochemical properties of the resulting solutions. Among the various surfactants tested, citric acid (0.15%) was chosen for the final working mixtures, as it assured a stable behaviour of the solutions prepared during the entire study. The nanoparticles were characterized in detail, and the physicochemical properties of the fluid were measured before and after atomization, to evaluate any possible particle loss in the liquid feeding system or retention in the atomizer. The nanofluids were sprayed using a pressure-swirl atomizer at 0.5 MPa injection pressure. Droplet size and velocity in the spray were probed using phase Doppler anemometry. For the range of experimental conditions covered here, the results show that liquid viscosity is an important parameter in predetermining the spray characteristics of nanofluids, as it affects the primary liquid breakup. Despite this, only a mild increase is observed in the nanofluids viscosity, mainly for higher concentrations of alumina, which was not sufficient to significantly affect the spray characteristics, except for a small decrease in the spray cone angle and the size of the atomized droplets. Hence, for cooling purposes, the atomization mechanisms are not compromised by the addition of the nanoparticles and their using is beneficial, as they enhance the thermal properties without a significant deterioration of other fluid properties such as viscosity and spray characteristics. Present spray characteristics promote liquid adhesion to the cooling surfaces and droplet size and velocity are kept within a range that is appropriate for spray cooling, following the literature recommendations and our analysis.

Verification of bleeding points in carotid blowout syndrome using guidewire manipulation.

Carotid blowout syndrome (CBS) is a catastrophic complication of aggressive treatment of head and neck cancer. Early detection of bleeding points with embolization is a life-saving procedure; however, some bleeding points may be difficult to identify. Our aim was to determine whether guidewire manipulation (GWM) could be used to verify bleeding point locations in patients with CBS. Of the 92 patients with CBS referred for embolization in a 5-year period, 14 men and one woman (mean age 58years) had bleeding points at locations that could not be definitely determined. We used GWM to verify the presence of these bleeding points. We assessed the anatomy of the ruptured arteries, technical details of GWM, and the angiographic and clinical outcomes. Bleeding points were difficult to detect because of the presence of small arterial pouches (n = 6) or multiple small arterial pouches (n = 9) in the unilateral or bilateral carotid arteries. Bleeding point locations were accurately identified using GWM in the internal carotid artery (n = 7), carotid bulb (n = 4), or common carotid artery (n = 4). Balloon-assisted GWM was applied in one patient. Fiber coils (n = 15) and/or liquid adhesives (n = 2) were used to occlude the affected artery. Endovascular management was technically successful in all patients and resulted in immediate cessation of hemorrhage without recurrence in a mean 22-month clinical follow-up. GWM is a simple and effective method for verifying bleeding points in ruptured arteries and preventing erroneous occlusion by embolization.

Major influence of the hydrophobic chain length in the formation of poly(3,4-propylenedioxypyrrole) (PProDOP) nanofibers with special wetting properties

Several species in nature have special wetting properties such as Lotus leaves or rose petals. Both the surface morphology and surface energy play a fundamental role. In particular, nanofibers were found to be exceptional surface structures due to a possible control in both water hydrophobicity and water adhesion as a function of their length, diameter, their orientation to the substrate or the spacing between them. Here, in the aim to prepare nanofibers with high liquid-repellent properties using conducting polymers, we have synthesized 3,4-propylenedioxypyrrole (ProDOP) derivatives with hydrocarbon and fluorocarbon chains in the 3-position, keeping the NH group free (important condition to lead to nanofibers thanks to hydrogen bonds). Different hydrocarbon and fluorocarbon chain lengths are studied. We obtain, for example, nanofibers of different size with octyl, decyl and C4F9 chains (intermediate hydrophobicity) with different liquid-repellent properties and liquid adhesion properties. More precisely, PProDOP-H8 is close to superhydrophobic properties (low water adhesion) while PProDOP-H10 is parahydrophobic (high water adhesion). This works could find many potential applications in the nanotechnology field as water harvesting surfaces, liquid separation membrane, and in anti-bioadhesion. Due to the presence of free NH groups, these materials could also be used as pH-sensitive materials while the nitrogen could also be easily functionalized.

Supercooled water droplet impact on superhydrophobic surfaces with various roughness and temperature

This paper investigates the impact behaviors between supercooled droplets and various superhydrophobic surfaces. We analyze the thermodynamic reason of the liquid adhesion at low temperature and discuss the influence of the substrate roughness, temperature and wetting property on the impact dynamics of supercooled droplets both experimentally and theoretically. The liquid adhesion results from the ice nucleation rather than the enhanced viscous effect induced by the low temperature. The dramatic increase of the liquid–solid contact area induced by the high-speed collisions between droplets and textured surfaces leads to a larger nucleation rate and a lower critical adhesion temperature. The analytical argument of the liquid–solid contact area fraction at different impact speed throws light on the understanding of the controversy if hierarchical superhydrophobic surfaces are icephobic at low temperature. Valuable suggestions are given that smooth superhydrophobic surfaces with nanoscale roughness near the critical nucleus radius perform better water-repellency against high-speed supercooled droplets.

Single-Droplet Multiplex Bioassay on a Robust and Stretchable Extreme Wetting Substrate through Vacuum-Based Droplet Manipulation.

Herein, a droplet manipulation system with a superamphiphobic (SPO)-superamphiphilic (SPI) patterned polydimethylsiloxane (PDMS) substrate is developed for a multiplex bioassay from single-droplet samples. The SPO substrate is fabricated by sequential spraying of adhesive and fluorinated silica nanoparticles onto a PDMS substrate. It is subsequently subjected to oxygen plasma with a patterned mask to form SPI patterns. The SPO layer exhibits extreme liquid repellency with a high contact angle (>150°) toward low surface tension and viscous biofluidic droplets (e.g., ethylene glycol, blood, dimethyl sulfoxide, and alginate hydrogel). In contrast, the SPI exhibits liquid adhesion with a near zero contact angle. Using the droplet manipulation system, various liquid droplets can be precisely manipulated and dispensed onto the predefined SPI patterns on the SPO PDMS substrate. This system enables a multiplex colorimetric bioassay, capable of detecting multiple analytes, including glucose, uric acid, and lactate, from a single sample droplet. In addition, the detection of glucose concentrations in a plasma droplet of diabetic and healthy mice are performed to demonstrate the feasibility of the proposed system for efficient clinical diagnostic applications.

Silica coating for interphase bond enhancement of carbon and AR-glass Textile Reinforced Mortar (TRM)

Abstract In this paper, we investigate the effect of silica nano-coating for interphase bond enhancement on the mechanical performance of Textile Reinforced Mortar (TRM) composite materials aimed at structural rehabilitation and strengthening. Alkali-resistant glass (ARG) and carbon fabric reinforcements are preliminarily treated via sol-gel deposition of SiO2 coating to promote bond formation capability with the mortar matrix. Optical and electron microscopy provide evidence of interphase bond enhancement. Mechanical performance is assessed both in traction, through uni-axial elongation of prismatic coupons, and in flexure, by three-point bending of laminated masonry bricks. Results are given in terms of mean strength curves, ultimate and design strength and strain values, cracked and uncracked moduli, mean crack spacing, mean crack width and energy dissipation. It is shown that mean absolute performance of silica coating offers a significant improvement over uncoated fabric, yet it is inferior to that of specimens which have been treated with a liquid partially-organic adhesion promoter (polymer coating). However, when design values are considered which incorporate the dispersion of experimental data, silica coating proves superior or at least equivalent to polymer coating, respectively for carbon and ARG fabric. These promising results describe the first application of silica nano-coating to fabric reinforced composite materials.

Interfacial Properties and Mechanisms Dominating Gas Hydrate Cohesion and Adhesion in Liquid and Vapor Hydrocarbon Phases.

The interfacial properties and mechanisms of gas hydrate systems play a major role in controlling their interparticle and surface interactions, which is desirable for nearly all energy applications of clathrate hydrates. In particular, preventing gas hydrate interparticle agglomeration and/or particle-surface deposition is critical to the prevention of gas hydrate blockages during the exploration and transportation of oil and gas subsea flow lines. These agglomeration and deposition processes are dominated by particle-particle cohesive forces and particle-surface adhesive force. In this study, we present the first direct measurements on the cohesive and adhesive forces studies of the CH4/C2H6 gas hydrate in a liquid hydrocarbon-dominated system utilizing a high-pressure micromechanical force (HP-MMF) apparatus. A CH4/C2H6 gas mixture was used as the gas hydrate former in the model liquid hydrocarbon phase. For the cohesive force baseline test, it was found that the addition of liquid hydrocarbon changed the interfacial tension and contact angle of water in the liquid hydrocarbon compared to water in the gas phase, resulting in a force of 23.5 ± 2.5 mN m-1 at 3.45 MPa and 274 K for a 2 h annealing time period in which hydrate shell growth occurs. It was observed that the cohesive force was inversely proportional to the annealing time, whereas the force increased with increasing contact time. For a longer contact time (>12 h), the force could not be measured because the two hydrate particles adhered permanently to form one large particle. The particle-surface adhesive force in the model liquid hydrocarbon was measured to be 5.3 ± 1.1 mN m-1 under the same experimental condition. Finally, with a 1 h contact time, the hydrate particle and the carbon steel (CS) surface were sintered together and the force was higher than what could be measured by the current apparatus. A possible mechanism is presented in this article to describe the effect of contact time on the particle-particle cohesive force based on the capillary liquid bridge model. A model adapted from the capillary liquid bridge equation has been used to predict the particle-particle cohesive force as a function of contact time, showing close agreement with the experimental data. By comparing the cohesive forces results from gas hydrates for both gas and liquid bulk phases, the surface free energy of a hydrate particle was calculated and found to dominate the changes in the interaction forces with different continuous bulk phases.

Thermoresponsive Mobile Interfaces with Switchable Wettability, Optical Properties, and Penetrability.

Liquid-based mobile interfaces, in which liquids are being utilized as structural long-term components, have shown their multifunctionality in materials science, such as the hydration layer of polyelectrolyte brushes used for artificial implants, stabilized lubricants for antibiofouling, anti-icing, self-cleaning, optical control, and so forth. However, these currently available systems do not usually show a response to environmental stimuli. Here, we describe a strategy for preparing thermoresponsive mobile interfaces made from novel silicone-based lubricants that display lower critical solution temperature and demonstrate their capabilities on controlling in situ water wetting and dewetting, thermo-gating penetration, and optical properties. These properties allow the mobile films to form a kind of erasable recording platforms. We foresee diverse applications in liquid transport, wetting and adhesion control, and transport switching.

Effect of gamma radiation on the surface and bulk properties of poly(tetrafluoroethylene)

The effect of gamma radiation on the contact angle θ, the work of adhesion γ SL for polar and nonpolar liquids, disperse and polar components of the surface energy γ S , the magnitude of bulk dielectric polarization P 0, and the dielectric increment Δe for sintered and non-sintered poly(tetrafluoroethylene) (PTFE) of suspension polymerization are studied. Sintered PTFE exhibits anomalously high growth of the studied parameters with an absorbed dose up to 500 kGy: Δe by more than four orders of magnitude, the work of adhesion of the polar liquid $$\gamma _{SL}^{{H_2}O}$$ by a factor of 1.5, the polar component of the surface energy γpol S by 20 times. The observed changes are found to be considerably larger than those expected from the viewpoint of the amplification of dipole–dipole and donor–acceptor molecular interactions with the participation of polar groups formed in poly(tetrafluoroethylene) upon irradiation. The similar behavior of Δe, $$\gamma _{SL}^{{H_2}O}$$ , and γpol S parameters depending on the exposed dose and subsequent annealing of the samples at 150°C is revealed. A unified mechanism for changes in the bulk polarization and surface properties caused by the formation in poly(tetrafluoroethylene) of long-lived electron–hole pairs is suggested.

Refinements Introduced in the Oddy Test Methodology

ABSTRACTThe ‘Oddy test’ is an accelerated corrosion test introduced in the 1970s at the British Museum to identify materials likely to emit volatile substances that could harm museum artefacts. It is carried out in many museums all around the world, but not always using the same methodology, which makes it difficult to compare and share test results between institutions. Refinements to the Oddy test methodology have been implemented at the British Museum over the last decade and the aim of this paper is to present these and promote consistency across institutions. The modifications introduced concern the method used to wash the glassware, the preparation of the metal coupons, and standard methods for preparing samples of liquid coatings, adhesives, and adhesive tapes. Finally, conducting Oddy tests is time consuming and measures employed at the British Museum to reduce the number of materials to be tested and streamline testing are described.

Experimental investigation of bubble and particle motion behaviors in a gas-solid fluidized bed with side wall liquid spray

Bubble and particle motion behaviors are investigated experimentally in a gas solid fluidized bed with liquid spray on the side wall. The particles used in the experiment are classified as Geldart B particles. The results reveal that when the fluid drag force is less than the liquid bridge force between particles, liquid distribute all over the bed. Bubble size increases as the increase of inter-particle force, then decreases owing to the increase of particle weight with increasing liquid flow rate. When the fluid drag force is greater than the liquid bridge force, liquid mainly distribute in the upper part of the bed. And it is difficult for the wet particles to form agglomerates. Bubble size decreases with increasing liquid flow rate due to the increasing of minimum fluidization velocity. Besides, the acoustic emission (AE) measurements illustrate that the liquid adhesion and evaporation on particles could enhance the particles motion intensity. Consequently, the bubble and particle behaviors change due to the variation in fluidized gas velocity and liquid flow rate should be seriously considered when attempting to successfully design and operate the side wall liquid spray gas solid fluidized bed.

容器口に刻んだ溝による液だれ防止の効果

容器口に刻んだ溝による液だれ防止の効果

Evaluation of adhesion of asphalt binders using wicking experiments

The objective of this study was to develop a methodology to evaluate the adhesion of liquids to porous by solids using wetting/wicking experiments. The surface area of porous materials significantly increases compared with that of their solid analogs. Hence, pores play an important role in the adhesion of resins and binders to solids. The authors developed an experimental protocol allowing one to evaluate the work of adhesion, a characteristic thermodynamic parameter of the liquid/porous solid pair. It is shown that for the determination of the work of adhesion, one needs to know the pore size distribution, the wicking constant of the wetting liquid and the surface tension of the liquid. Asphalt binders and different rocks were studied to illustrate the methodology.

A novel approach for dry powder coating of pellets with Ethylcellulose. Part I: Evaluation of film formulation and process set up

An innovative dry powder coating technology was developed in a high-shear granulator using ethylcellulose (E10) as polymer. Several solid plasticizers were investigated with the aim of decreasing the polymer Tg at least to the highest possible working temperature (80°C). DSC analysis of physical mixtures of E10 and plasticizers evidenced that lauric acid (LA) was the most effective plasticizer. In order to reach the target temperature a liquid plasticizer, oleic acid (OA), was introduced in the coating formulation. Free films were then prepared and the target minimum film forming temperature (MFFT) was established in the range 70–80°C. Depending on the LA:OA weight ratio, Kollidon VA64 was included to decrease the LA recrystallization, while talc served as anti-sticking agent. Curing at the MFFT ensured the formation of homogeneous and stable films with good stability on storage. The dry powder coating process of placebo pellets was then developed, consisting of a combination of liquid assisted and thermal adhesion methods. The best coating formulations in terms of yields, coating efficiency (expressed as Relative Standard Deviation of the weight applied) and low pellets aggregation were based on E10:LA:OA in a weight ratio of 65:20:15 and 60:20:20. Moreover pellets remained stable after 1year of storage (25°C/60% R.H.).

Paper‐Based Hydrophobic/Lipophobic Surface for Sensing Applications Involving Aggressive Liquids

A paper‐based hydrophobic/lipophobic surface with high liquid drop adhesion capable of carrying out sensitive biochemical assays directly is reported. Hydrophobic sol‐gel derived fluoroalkyl‐silica is used to develop the hydrophobic/lipophobic surface, which demonstrates superior confining abilities. The reported hydrophobic/lipophobic surface could retain aggressive liquids such as organic solvents and surfactant solutions whereas the methyl‐silica based surface fails to function. Because of the superior confining abilities, this paper‐based hydrophobic/lipophobic surface is competent for sensitive heavy metal ions detection and bacteria assay where aggressive liquids are necessarily used. The condensing‐enrichment effect on the hydrophobic/lipophobic surface renders this paper‐based analytical device (PAD) high sensitivity, and the high adhesion of the surface offers the PAD robustness. Facile fabrication of such surface and ease of operation for subsequent sensing promise a great potential for the PAD.

Design and Fabrication of a Tip‐Like ZnO Nanotube Array Structure with Condensate Microdrop Self‐Propelling Function

AbstractHere, we present a type of tip‐like nanotube array with condensate microdrop self‐propelling (CMDSP) function. Based on the basic principle that condensate microdrops can self‐remove via coalescence‐released weak surface energy as long as interface adhesion induced energy dissipation is sufficiently low, we design tip‐like nanotubes with extremely low solid–liquid interface adhesion. To verify the feasibility of this idea, we propose a strategy of preferential etching of six corners and the interior of ZnO nanopencils to achieve tip‐like nanotubes. Our studies demonstrate that this nanostructure can be achieved by immersing ZnO nanopencils in 0.006 m HCl aqueous solution at 80 °C for 3 h. After silane modification, the resulting nanostructure shows CMDSP function. This work offers a new avenue for developing CMDSP functional films, which can find a variety of technological applications such as moisture self‐cleaning, antifrosting and enhancing heat transfer.

Tailoring rheological properties of uncrosslinked water-borne pressure-sensitive adhesives by means of polymer maximum volume fraction

Pressure-sensitive adhesives (PSAs) based on butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), methyl methacrylate (MMA), vinyl acetate (VAc), and acrylic acid (AA) were prepared via semicontinuous emulsion polymerization, the obtained latexes having nanometer particles, narrow monomodal particle size distribution, and concentrations close to maximum packing fraction. The rheological behavior of liquid adhesives was described using the generalized Maxwell model and the observed differences are a consequence of different particle surface polarity. As the copolymers polarity increases by incorporation of VAc, the amount of surfactant deposited onto the particles decreases, which leads to lower viscosities and higher values for critical volume fraction of polymer. The viscoelastic properties of solid adhesives were investigated by Dynamic Mechanical Analysis. Copolymers of MMA have higher glass transition temperatures than what would be expected theoretically, indicating a higher cohesive strength for these copolymers. Moreover, MMA copolymers have lower molecular masses between entanglements than those containing VAc. All these viscoelastic characteristics are in very good agreement with the adhesive performance characteristics observed.

Liquid Crystalline Polymers Compatibilization and Adhesion Enhancement by Reactive Blending in Post-Consumers PET’s

A method for PET mechanical properties enhancement by reactive blending with HBA/HNA Liquid Crystalline Polymers for in situ highly fibrillar composites preparation is presented. LCP/PET blends were reactive extruded in presence of Pyromellitic Di-Anhydride (PMDA) and then characterized by Differential Scanning Calorimetry, Thermally Stimulated Currents and tensile mechanical properties. The formation of specific macromolecular structures, where the PET, the LCP and the reactive additive are involved, has been hypothesized in the reactively extruded blends from TSC analysis evidences. The use of a reactive additive improved the matrix LCP compatibilization and adhesion as indicated by the SEM analysis and mechanical testing. Moderate amounts of LCP in the PET (0.5 and 5%) and small amounts of thermo-active and reactive compatibilizer in the blend (0.3%) were found to significantly improve LCP melt dispersion, melts shear transfer and LCP fibril formation and adhesion. Blends of PET and LCP containing the compatibilizer favored the formation of a well dispersed and homogeneous fibrillar phase whose particle size distribution did not show great coarsening and coalescence leading to significant elastic properties improvements from 0.8 for not compatibilized to 3.1 GPa for compatibilized 0.5% LCP loaded PET blends that was even higher than those expected from ordinary theoretical calculation. This unexpected improvement was probably due to the presence of two distinct phases' supra-molecular structures involving PET-LCP and PMDA.

Zwitterionic Nanofibers of Super-Glue for Transparent and Biocompatible Multi-Purpose Coatings.

Here we show that macrozwitterions of poly(ethyl 2-cyanoacrylate), commonly called Super Glue, can easily assemble into long and well defined fibers by electrospinning. The resulting fibrous networks are thermally treated on glass in order to create transparent coatings whose superficial morphology recalls the organization of the initial electrospun mats. These textured coatings are characterized by low liquid adhesion and anti-staining performance. Furthermore, the low friction coefficient and excellent scratch resistance make them attractive as solid lubricants. The inherent texture of the coatings positively affects their biocompatibility. In fact, they are able to promote the proliferation and differentiation of myoblast stem cells. Optically-transparent and biocompatible coatings that simultaneously possess characteristics of low water contact angle hysteresis, low friction and mechanical robustness can find application in a wide range of technological sectors, from the construction and automotive industries to electronic and biomedical devices.