Surface Energy Adhesion Research Articles

Novel Glycidyl Carbamate Functional Epoxy Resin Using Hydroxyl-Terminated Polybutadiene

Herein, a novel glycidyl carbamate functional epoxy resin (GCE) is synthesized by the additional reaction of the isocyanate group of tolylene diisocyanate (TDI) with the hydroxyl group of hydroxyl-terminated polybutadiene (HTPB) and glycidol. The successful synthesis of the GCE is confirmed by FT-IR and 1H NMR spectroscopy. Furthermore, a dual-curing adhesive system is developed using acrylic acid and trimethylolpropane triacrylate with varying GCE contents, and its adhesive performance is assessed by testing adhesive strength, pencil hardness, and surface energy. As a result, the dual-cure adhesive containing 0.2 mol of GCE demonstrates an impressive adhesive strength of 11.1 MPa, a pencil hardness of B, and surface energy comparable to that of standard polycarbonate film.

The screening of iron oxides for long-term transformation into vivianite to recover phosphorus from sewage

The reducibility of iron oxides, depending on their properties, influences the kinetics of dissimilatory iron reduction (DIR) during vivianite recovery in sewage. This study elucidated the correlation between properties of iron oxides and kinetics of DIR during the long-term transformation into vivianite, mediated by Geobacter sulfurreducens PCA and sewage. The positive correlation between surface reactivity of iron oxides and reduction rate constant (k) influenced the terminal vivianite recovery efficiency. Akaganeite with the highest adhesion work and surface energy required the lowest reduction energy (Ea), obtained the highest k of 1.36 × 10–2 day-1 and vivianite recovery efficiency of 43 %. The vivianite yield with akaganeite as iron source was 76–164 % higher than goethite, hematite, feroxyhyte, and ferrihydrite in sewage. The distribution of P with akaganeite during DIR in sewage further suggested a more efficient pathway of direct vivianite formation via bio-reduced Fe(II) rather than indirect reduction of ferric phosphate precipitates. Thus, akaganeite was screened out as superior iron source among various iron oxides for vivianite recovery, which provided insights into the fate of iron sources and the cycle of P in sewage.

Effects of liquid lubricants on the surface characteristics of 3D-printed polylactic acid

In this study, 3D-printed Polylactic acid (PLA) specimens were manufactured and polished using various lubricants to assess their surface, friction, and wear characteristics. After polishing, the surface roughness decreased by approximately 80% compared with that before polishing, except when acetone was used as the lubricant. In particular, under deionized (DI) water and acetone lubrication conditions, the friction coefficient decreased by 63% and 70%, respectively, whereas the specific wear rate decreased by 88% and 83%, respectively, compared with the unpolished specimens. In the case of dry polishing, adhesion, friction, and wear increase owing to surface damage. Ethanol and IPA polishing resulted in hydrolysis and increased friction, but slightly decreased wear rates. The surface of the specimen polished with acetone dissolved and became very rough. Only the surface polished with DI water exhibited hydrophobic properties. When acetone and DI water were used as lubricants, the surface adhesion force, adhesion energy, friction coefficient, and wear rate were lowest. The finite element analysis results showed that the polished surface exhibited stable contact pressure and friction force, while the unpolished surface showed large fluctuations in contact pressure and friction force owing to the laminated pattern. These results suggest that the polishing process is crucial for improving the surface characteristics and mechanical performance of 3D-printed PLA parts.

Comparative study on graphene oxide and sulfonated graphene oxide reinforced polyethersulfone-based cation-exchange membrane

In this research, polyethersulfone/sulfonated graphene oxide (PES/SGO) heterogeneous cation exchange membranes were fabricated by the mold casting method. The sulfonation of GO was carried out using the diazonium salt of sulfanilic acid. The properties of the synthesized GO and SGO were compared in terms of chemical structure, morphology, surface charge, crystallinity, and thermal stability. The variations in surface morphology and roughness, hydrophilicity, dimensional stability, and ionic conductivity of the PES-based membranes as a function of GO and SGO content were investigated. Results revealed that SGO enjoyed a higher level of oxygenated groups contributing to its higher surface charge. SGO also tolerated a higher temperature before being fully decomposed due to the presence of the sulfur-containing groups. A finer nanostructured morphology was observed in the SGO-containing membranes, resulting in a considerably lower surface roughness of these membranes than the corresponding GO-based membranes. The membrane comprising 10 wt% SGO showed the lowest surface roughness of 88 nm, and the highest water uptake of 16.66 %, ion-exchange capacity of 1.12 meq g-1, and the lowest charge transfer resistance of 3.6 Ω and area resistance of 0.9 Ωcm2. This was accompanied with a considerable increment in the permselectivity and cation (Na+) transport number of this membrane to 95.9 % and 97.5 %, respectively, due to the higher surface adhesion energy of 94.57 J m-2 and higher Na+ flux of 4.43×10-7 mol m-2 s-1, which were significantly higher than that obtained for the corresponding PES-based membrane containing 10 wt% GO. Furthermore, a lower weight loss and resistance change were observed for PES/SGO after being exposed to the Fenton reagent for 9 h, indicating the impact of the sulfonated groups on the oxidative stability enhancement of the membrane.

Spider silk-inspired heterogeneous interphase featuring hybrid interaction for simultaneously improving the interfacial strength and fracture toughness between carbon fiber and epoxy by regulating hydrogen bond density

Designing advanced fiber-reinforced polymer composites through biological inspiration proved to be a crucial strategy for overcoming limitations in simultaneously enhancing the strength and toughness of composites. To achieve simultaneous improvement in the interfacial strength and toughness between carbon fiber (CF) and epoxy, a spider silk-inspired interphase featuring hybrid interaction was constructed by introducing hyperbranched polyamide-amine (HPAA) and graphene oxide (GO) onto the surface of CF. The results suggested that manipulating the feed ratio to adjust the branching degree of HPAA allowed for the attainment of various hydrogen bond densities. The fiber surface with high hydrogen bond density provided more hydrogen bond interaction sites to promote the deposition of GO. Benefitting from the ameliorative interfacial adhesion force, surface energy and interface thickness, impressive improvements of 94.5 % and 110.0 % in respective interfacial strength and fracture toughness over those of untreated CF/EP composites were achieved for functionalized CF/EP composites. The enhancement mechanism of interfacial performance was attributed to the formation of a “nano-fishnet” structure, which improved the stress transformation efficiency and consumption of external energy absorbed by hydrogen bonds. The method of regulating the branching degree of hyperbranched polymers and hydrogen bond density has opened an advanced way for surface modification of high-performance fibers.

Effect of Pigment-Acrylic Binder Ratio on the Surface and Physical Properties of Resin Finished Leather

The current study attempts to investigate the surface phenomenon and physical characteristics of leather finished with brown pigment and different types of acrylic binders. Using the contact angle measurements of three different liquids on the above finished leathers and films, the surface energy and work of adhesion were evaluated. The pigment to acrylic binder ratio (PABR) for best adhesion of finish film on the leather surface was optimized using the contact angle goniometer. Different types of acrylic binder films were coated and their surface behaviour was studied. The crust leather was coated with different types of pigment-acrylic binder (Very Soft, Soft and Medium Soft) finish formulations. The contact angle of both the acrylic films and the PABR finished leathers were measured against Water, Dimethyl sulfoxide (DMSO) and Hexadecane (HD). According to the study’s results, the surface properties of finished leather were directly related to the degree of wetting. The PABR was found to be effective at 1:3 for very soft binder, 1:2.5 for soft, 1:2 for medium soft binders due to higher contact angle and lower surface energy values (γsv). At 1:3 and 1:2.5, the contact angle of very soft and soft binder leather was 82.62° and 83.45° and for medium soft binder it was 82.67° at 1:2 ratio. The surface energy values of optimized PABR of very soft binder (1:3) was 28.29 (mN/M), soft binder (1:2.5) was 27.50 (mN/m) and medium soft binder (1:2) was 29.27 (mN/m). The optimized PABR work of adhesion values of very soft binder, soft binder and medium soft binder was 82.15 (mJm-2), 81.11 (mJm-2), 82.09 (mJm-2). In order to correlate the observed surface properties with leather finish properties, finished leathers were tested for finish adhesion, vamp flexing value, water vapour permeability, wet and dry rub fastness. According to the water vapour permeability, soft and medium binder showed good permeation due to the uncovering of nanopores. But the adhesion, grain crack resistance and grain smoothness were higher in the case of the soft binder. Overall leather properties divulges that the pigment to binder ratio and the type of binder plays an important role in surface properties of the finished leather. This study enables us to determine the optimal PABR for effective finish properties to meet the required leather standards for various usage, as well as better utilisation of finishing chemicals.

Striking a Balance: Exploring Optimal Functionalities and Composition of Highly Adhesive and Dispersing Binders for High‐Nickel Cathodes in Lithium‐Ion Batteries

AbstractNickel‐rich layered oxide, LiNixCoyMnzO2 (NCM, x > 0.8), has emerged as a promising cathode material for lithium‐ion batteries due to its high specific capacity and energy density. However, there remains a challenge regarding NCM degradation during cycling, associated with interfacial side reactions and microcrack formation. Herein, a functional poly(norbornene‐co‐norbornene dicarboxylic acid‐co‐heptafluorobutyl norbornene imide) (PNCI)‐based binder system is introduced, with controlled functionalities and monomer compositions, to preserve the structural integrity of NCM. The PNCI binder system incorporates three different norbornene‐derived monomers with distinct functionalities, allowing for multifunctionality, including electro‐chemo‐mechanical stability, strong adhesion, and dispersibility. By systematically adjusting the molar composition of the PNCI binders, the overall binder characteristics are fine‐tuned, optimizing the adhesion and dispersion of electrode components. The optimized PNCI binder, with desired adhesion strength, surface energy, and polarity, plays a crucial role in facilitating the formation of a uniform electrode structure with a high areal mass loading of NCM, ensuring long‐term cycling stability. This study highlights the significance of striking a balance between functionalities and composition in binder systems to achieve high‐performance NCM cathodes.

Grafted Alkene Chains: Triggers for Defeating Contact Thermal Resistance in Composite Elastomers.

The pursuit of enhancing the heat transfer performance of composite elastomers as the thermal interface materials (TIMs) is a compelling and timely endeavor, given the formidable challenges posed by interfacial thermal transport in the domains of energy science, electronic technology, etc. Despite the efficacy of phase change materials (PCMs) in enhancing composite elastomers' interfacial compatibility, thereby reducing contact thermal resistance for heat transfer improvement, their leakage post-transition has impeded the widespread adoption of this approach. Herein, a strategy is proposed for developing a solid-solid phase change composite elastomer by grafting alkene chains onto the crosslink network to eliminate the possibility of leakage. A series characterization suggest that the resulting material possesses a self-adjusting interfacial compatibility feature to help reduce contact thermal resistance for heat transfer facilitating. The investigations on adhesion strength and surface energy reveal that the presence of amorphous grafted alkane chains at the interface facilitates easier absorption onto the contacting solid surface, enhancing intermolecular interactions at the interface to promote across-boundary heat transfer. By integrating these findings with the thermal performance evaluation of composite elastomers using a real test vehicle, valuable insights are gained for the design of composite elastomers, establishing their suitability as TIMs in relevant fields.

Stiffening of polydimethylsiloxane surface as result of exposure to low‐pressure argon discharge plasma

AbstractPolydimethylsiloxane (PDMS) surface has been exposed to negative glow discharge plasma of a low‐pressure discharge in pure argon for a duration varying from 10 s to 2 min. Shallow atomic force microscopy indentation experiments were performed to investigate the effect of plasma treatment on PDMS surface stiffness and adhesion energy to the silicon nitride indenter surface. The results showed an important increase in Young's modulus and a slight increase of work of adhesion. X‐ray photoelectron spectroscopy investigation of plasma‐treated PDMS surface showed a decrease of atomic content of carbon accompanied by an increase of oxygen content and suggests that the stiffening of PDMS surface can be attributed to generation of new cross‐linking Si–O–Si and Si–CH2–CH2–Si bonds between PDMS molecules.

Investigations on wetting and structural behavior using CaF2-SiO2-CaO-22.5%TiO2 SMAW electrode coating for AUSC applications

This study investigates the structural behavior and high-temperature wettability of a CaF2-SiO2-CaO-22.5%TiO2 shielded metal arc welding electrode coating for advanced ultra-supercritical power plant applications. The wettability parameters were measured, including contact angle, spread area, adhesion energy, and surface tension. Extreme vertices mixture design approaches were used to develop 13 different electrode coatings. To determine the contact angle at solid/liquid interface, circular pellets were made from powder samples and heated inside the furnace at 1125°C at a constant heating rate. Young's and Boni's equations are used to calculate the surface tension value for 13 coated samples using the calculated contact angle. Adhesion energy for 13 coated samples is calculated using Dupre's equation. Phases and structural behavior of coating samples were measured by Fourier transform infrared spectroscopy and X-ray diffraction. The developed regression model estimates the impact of primary ingredients and their interaction on the calculated wettability characteristics. CaF2.SiO2, CaO.SiO2, and CaO.CaF2 binary mixture is the more favorable and substantially impacts contact angle, whereas ternary interactions of CaO.SiO2.CaF2 shows an opposite effect on contact angle. Coating numbers 2 and 10 give better wetting behavior and spread area due to the low value of contact angles. Individual ingredient shows an increasing effect on surface tension and adhesion energy. Ternary component of CaO.CaF2.SiO2 is favorable and shows an increasing impact on adhesion energy.

Effect of roughness small scales on the adhesion of randomly rough surfaces with high fractal dimension

Surface roughness affects several tribological phenomena like adhesion. In this work, JKR-like experimental tests were performed between Polydimethylsiloxane (PDMS) spherical samples and flat glass substrates with different surface roughness properties. Data were interpreted in the light of classical JKR theory. We find that adhesion is destroyed by roughness in agreement with the most common and well-known results in the literature. However, from the analysis of the Power Spectral Density (PSD) of the surfaces, it emerges that the smaller scales of roughness have a greater influence on the surface adhesion energy in the range of the high fractal dimensions (D > 2.5). In this range, for surfaces with the same root mean square (RMS) roughness amplitude hrms , which is mainly affected by large scale roughness, the pull-off force (i.e., the maximum tensile force reached during the retracting phase) is observed reducing by increasing the RMS slope of the surface roughness , that is by changing the roughness content at the small scales. This result agrees with recent theoretical findings and has never been shown experimentally in the literature to the best of our knowledge.

Effective friction in adhesive mixtures intended for inhalation: Simulation of oblique impact of adhesive units

Oblique impact between adhesive units was studied using the Discrete Element Method (DEM) as a means to assess the effective friction coefficient and its dependence on particle shape, surface coverage ratio (SCR; 0.5, 0.75 and 1) and impact angle ( 1 5 ∘ − 7 5 ∘ ) in a low handling velocity regime (0.6 – 1.6 m/s). Adhesive units were created in silico from a spherical carrier particle (100 μm diameter) and monodisperse fine (drug) particles (3 μm large) of a spherical, triangular bipyramidal or tetrahedral shape. The particle interaction was modeled using the Hertz-Mindlin contact model with JKR adhesion (surface energy 0.03 J/m 2 ). A total of over 300 simulations were performed and the effective friction coefficient was extracted from the normal and tangential forces experienced by the carrier particles. The adhered fines resulted in a significantly reduced friction coefficient in comparison to the bare carriers but no additional reduction was observed with increasing SCR, suggesting a saturation already at an SCR of 0.5. The effective friction coefficient was independent of the impact velocity for relative velocities over 1 m/s. The impact angle had a significant effect on the friction coefficient, with head-on type collisions (15°) resulting in the lowest and grazing-type collisions (75°) the highest values. This was especially pronounced for the spherical fines whereas the triangular bipyramidal and especially the tetrahedral fines resulted in a more modest dependence on impact angle but overall considerably higher friction coefficients. These results could be used to better understand and formulate adhesive mixtures. • Adhesive units with different fine shapes were formed in-silico. • Binary collisions with different impact angle to study effective friction. • Effective friction is signifcantly lower compared to bare carrier particles. • Tetrahedral shape with angles towards grazing impact showed highest friction.

Preparation and performance of an asphalt pavement sealant with waterborne epoxy resin

• The design content of WER in SBS modified emulsified sealant was identified. • Effect of WER on the adhesive strength of WER-SBS-EA was investigated. • Ultraviolet aging characteristics of WER-SBS-EA were studied at different radiation times. At present, crack sealing is a widely accepted routine preventative maintenance practice of asphalt pavements. Successful crack sealing is perceived to be of the primary importance by maintenance engineer because if not properly exercised, excessive aging, extended cracking, and high temperature flow deformation of pavements will be resulted. In this study, the waterborne epoxy resin (WER) and styrene butadiene styrene (SBS) composite modified emulsified asphalt sealant (WER-SBS-EA), was prepared. The optimum contents design of modified emulsified asphalt (SBS-EA) was identified by the shear strength test. Then, the properties of the WER-SBS-EA were investigated by contact angle, pull-off, and indoor accelerated ultraviolet (UV) aging tests. The results showed that the shear strength of the WER-SBS-EA was increased by WER, and the optimum proportioning of the WER: SBS-EA was 2:3. The WER-SBS-EA, with a contact angle greater than 90°, i.e. was hydrophobic. The surface energy and work of adhesion of the WER-SBS-EA were higher than those of the SBS-EA, which means that the WER-SBS-EA has good bonding strength. As the temperature and immersion time increased, the bonding strength of the WER-SBS-EA was decreased but still higher than that of the original SBS-EA. In addition, the shear strength of the WER-SBS-EA after aging for 16 days is still 44.4 % higher than that of the unaged SBS-EA; hereby the presence of WER in the asphalt sealant can help counteract the stiffening effect resulting from oxidative hardening. Therefore, the WER-SBS-EA can be used for preventive maintenance and is of great significance for extending the service life of the asphalt pavement.

Investigation on TaC (1 1 1)/TiC (1 1 1) interface for coating with high-performancse corrosion resistance: First-Principle calculations and experiments

In this study, first-principle calculation is used to investigate the TiC (111)/TaC (111) interface in terms of surface energy, work function, adhesion energy, and electronic structure. Compared with TaC (111), the TiC (111) surface shows a higher surface energy and a lower electronic work function. The surface passivation of TiC can be achieved by covering the TaC layer. Besides, the interface bonding configuration of TiC (111)/TaC (111) that relates to corrosion resistance is studied in detail. In experimental verification, a set of TiC-based coatings are investigated by potentiodynamic polarization, potentiostatic polarization, and impedance. Compared with pure TiC and TiC/C coatings, the TaC/TiC/TaC/C structure exhibits the lowest corrosion current density of 0.28 μA cm−2 and the lowest corrosion tendency. SEM observation also reveals its minimal morphological damage after potentiostatic polarization. The modified multilayer coating presented in this work is successfully used as the protecting structure of stainless-steel bipolar plate, which may be of great significance to the light weight metallic bipolar plate in proton exchange membrane fuel cells.

Vibration-induced detachment of droplets on superhydrophobic surfaces

Vibration is a robust and efficient method for droplet removal from superhydrophobic surfaces. In the present work, we experimentally investigated the dynamics of droplets on vibrating superhydrophobic surfaces, and established a mass-spring-damper theoretical model, to clarify the underlying physics of vibration-induced droplet detachment. Different droplet oscillation patterns were experimentally observed, namely, the droplet motion is in the same/opposite direction with the substrate when the vibration frequency is less/higher than the resonance frequency, respectively, and the transition occurs at the resonant frequency. The motion of the droplet is found to be composed of a transient response by the droplet free oscillation and a steady-state response by vibrating substrates. The critical condition for droplet detachment was identified to be the droplet energy (sum of the surface energy and kinetic energy) exceeds the surface adhesion energy. At the resonance frequency, the vibrational energy of the substrate is progressively accumulated in the droplet with the highest energy maintenance efficiency, and a small amplitude of vibration could therefore yield droplet detachment. The separation time shortens with the vibration amplitude and minimizes at the resonance frequency at a given amplitude. Our findings are helpful for the utilization of vibrating superhydrophobic surfaces for droplet removal.

Ameliorating properties of castor oil based polyurethane hybrid nanocomposites via synergistic addition of graphene and cellulose nanofibers

Castor oil based polyurethanes were reinforced with cellulose nanofibers derived from hemp and graphene nanosheets to yield hybrid nanocomposites using ultrasonication coupled with high shear homogenization. Morphology of nanocomposites assessed using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) elucidated 3D network of CNFs and GNS in polyurethane matrix. The paramount properties were obtained with equal amounts of CNFs and GNS attributed to higher degree of crystallinity. Thermal stability was evaluated using Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC), which exhibited a substantial increase in peak degradation temperature by 24 °C and glass transition temperature by 36 °C, with mere addition of 1% CNFs and GNS each. The mechanical properties improved by more than 400% attributed to the presence of interconnecting network of GNS and CNFs, initiating enhanced interactions amongst polymer and nanofillers, established by X-Ray photoelectron spectroscopy (XPS). Strong intermolecular bonding between the fillers and the polymer matrix reduced the phase separation, facilitating migration of soft segments to the surface increasing the water contact angle by 32°. The decrease in surface energy and work of adhesion contributed to hydrophobicity of nanocomposites. The improved properties of hybrid nanocomposites ascertain their potential applications in protective coatings and automobile parts..

Growing twisted bilayer graphene at small angles

Growing twisted bilayer graphene at small angles

Calibration of DEM for Cohesive Particles in the SLS Powder Spreading Process

In this paper, a new DEM calibration procedure based on two different types of procedures to compare simulation with experiments is proposed. The aim is to find the values of the interfacial adhesive surface energy and the coefficient of rolling friction between the particles to be used in the simulation. The approach adopted is the so-called Bulk Calibration method. The experimental values of the angle of repose and unconfined yield strength, found with a static testing method and by shear testing, respectively, are compared, respectively, with the angle of repose, found in a simulation reproducing the experimental procedure, and the unconfined yield strength, obtained from an idealized uniaxial testing procedure. The simulated DEM particles are spheres equipped with the Hertz Mindlin with JKR contact model. The results suggest that a bulk calibration approach is not able to provide results that are consistent with two simple bulk property evaluations and, therefore, direct ways to estimate the surface energy based on the evaluation of interparticle forces, for example, should preferably be adopted.

Frank-van der Merwe growth in bilayer graphene

Frank-van der Merwe growth in bilayer graphene

Effect on hydrophobicity and antimicrobial behavior of epoxy resin due to silane functionalized TiO2 as nanofillers

4-Aminobutyltriethoxysilane functionalized TiO2 nanoparticles (TiO2-ABTES) dispersed diglycidyl ethers of bisphenol-A (DGEBA-GY260) were studied for antimicrobial applications. Epoxy nano-hybrid coatings of four different concentrations (1, 3, 5 and 7 wt %) were developed using TiO2-ABTES as the dispersed phase and a commercially available DGEBA as the matrix phase. Triethylenetetramine (TETA) used to cure the nanocomposites films. The structural characteristics of these materials were investigated by Fourier transform infrared spectral studies, Scanning electron microscopy and atomic force microscope analysis. The surface characteristics of the samples were estimated from contact angle measurements and calculated surface free energy and adhesion energy. The bacteriological tests were done using the agar diffusion method with different concentrations of TiO2-ABTES. The antimicrobial activity test noted that the antimicrobial activity of 7 wt% TiO2-ABTES nanoparticles loaded epoxy nanocomposite film has a better inhibition zone against all pathogens under study.