Chemical Adhesion Research Articles

Stripping at the Bitumen–Aggregate Interface: A Laboratory Method To Assess the Loss of Chemical Adhesion

Moisture damage, cracking, and deformation are the three chief distresses caused by traffic and climate during the service life of an asphalt pavement. One manifestation of moisture damage is the loss of bond between bitumen and aggregate, resulting in the displacement of the bitumen in a process called stripping. While numerous tests try to evaluate moisture damage in the laboratory, most of them show poor correlation with field performance. A fuller understanding of stripping is still needed to enable paving technologists to predict and prevent the effects of moisture damage. This study aims to develop a new stripping resistance evaluation technique, wherein adhesion is measured exclusively as a function of the chemical interaction between bitumen and aggregate. A key element of the evaluation technique discussed herein uses a time-lapse image analysis method to characterize the dynamic wetting of precisely applied bitumen droplets on the surfaces of polished mineral aggregates during immersion in a the...

Effect of the combined treatment with inorganic and organic agents on the surface hardening and adhesion properties of cement-based materials

In this paper, a stable but highly reactive potassium silanol coupling agent (PSCA) solution for cementitious materials repair was prepared via the cationic complexation method under −20 °C. Furthermore, here we report an innovative magnesium fluorosilicate (MF)- and PSCA-combined treatment for repairing the surface of old cement-based materials. The effect and mechanism of MF and PSCA on the chemical reaction, adhesion properties, durability, and surface morphology of cement-based materials were systematically studied. The results revealed that MF acts to immobilize soluble Ca2+ (with the dissolution rate of Ca2+ decreased by 62.53%), to harden the surface (with an increase from 0.975 GPa to 2.420 GPa), as well as to roughen the surface (with the roughness average increased by 80.61%). Moreover, after spraying the surface with PSCA, MF promotes cross-linking by forming a potassium salt with K+ to form organic-inorganic chemical bonds. Indeed, the adsorption orientation effect formed by MF and PSCA leads to a good coupling effect; therefore, the leaching rate of Ca2+ is reduced by 62.53%. By adopting such a surface-treatment method, the slant-shear strength and the pull-off adhesion strength after the repair are increased by ~12% to 40%, while the water aging resistance is remarkably improved.

Investigation on bond strength between recycled aggregate concrete (RAC) and steel tube in RAC-filled steel tubes

This paper reviews the previous studies on bond behaviour of concrete-filled steel tubes (CFST) and recycled aggregate concrete-filled steel tubes (RAC-FST). The bond behaviour between the steel tube and the recycled aggregate concrete (RAC) of RAC-FST is experimentally investigated then. A series of push-out tests on 56 RAC-FST specimens are conducted with parameters of cross-section type, cross-sectional dimension, strength of RAC, replacement rate of recycled coarse aggregate and interface treatment (i.e. oilin, polishing). Mechanism of the effects of chemical adhesion, micro-interlocking and macro-interlocking on the bond strength is discussed and investigated based on the testing results. The analytical results show that the cross-section type and cross-sectional dimension are two main parameters that influence the bond strength between the steel tube and the RAC core. It can be concluded that, in general, the bond behavior of the RAC-FST is similar to that of the steel-concrete surface in concrete-filled steel tubes (CFST). Finally, empirical formulas are proposed for the calculations of the bond strength between the core concrete and the outer steel tubes.

Efficiency of Hybrid Sintering Technology for Cemented Carbide Diamond-Containing Composites with Impregnation, Including Thermal Diffusion Metallization of Diamonds

For the enhancement of chemical and mechanical adhesion of natural diamond particles with a hard-alloy matrix during the synthesis of diamond-abrasive composites the hybrid technology which combined in one technological process the thermal diffusion metallization of diamond particles and sintering by the developed scheme of the self-dosed impregnation is proposed. This technology does not include a reheating of the metallized coating that causes its destruction and enhances graphitization of diamond thus limiting the application of metallization method for improvement of diamond retention and creation of high-functional composites for diamond tools. Formation and preservation of adhesion-durable metallized coating is confirmed by experiments simulating the conditions of high temperature interaction of diamond with a carbide-forming metal and a hard-alloy matrix during the sintering of special samples using the regimes of developed technological process. The structural and phase state of the transition zone is studied by scanning electron microscopy, X-ray structure analysis and X-ray phase analysis of the partition surfaces of the contact zone between the diamond and the matrix obtained by tensile testing of special samples. Comparative service properties tests of prototype and control samples of diamond dressers confirmed efficiency of the developed hybrid technology for the creation of diamond tools.

Structural-Phase State of the Diamond-Matrix Transition Zone in Hard-Alloy Diamond-Containing Composites with Diffusion Metallization of Diamonds during Sintering with Impregnation

The conducted study belongs to a field of fundamental and application-oriented issues of interphase interaction and formation of interfacial layers between a filler and matrix during the synthesis of composite systems. The factors determining the strength of the diamonds retention in a hard-alloy matrix of abrasive composites obtained by the hybrid synthesis technology with thermal diffusion metallization of diamond particles and sintering by a scheme of the self-metering impregnation were studied. Chemical composition, morphology and distribution of the reaction products, the nature of the resulting carbon phases in the contact zone between the diamond and matrix were investigated using scanning electron microscopy, X-ray phase analysis, Raman spectroscopy and atomic force microscopy. It was found that the increase of physical and chemical adhesion of diamond with the matrix during the synthesis of composites by the developed technology occurs due to the formation of high nano- and submicronic roughness of the diamond surface, formation of island-type metallized coating, dense filling of gaps by nanoscale layers of metal-infiltrate. Free carbon (graphite) was found in small quantities in the form of micron dimension separate inclusions. The revealed multilevel hierarchy of the high-structured morphological forms of the elements of the transitional layers has provided the solidity and strength of the joint between diamond and matrix.

Investigation of Bonding Behavior of FRP and Steel Bars in Self-Compacting Concrete Structures Using Acoustic Emission Method.

To extend understanding of the bonding behavior of fiber reinforced polymer (FRP) and steel bars in self-compacting concrete (SCC), an experimental series consisting of 36 direct pull-out tests monitored by acoustic emission (AE) were performed in this paper. The test variables involved rebar type, bar diameter, embedded length, and polypropylene (PP) fiber volume content. For each test, the pull-out force and free end slip were continuously measured and compared with the corresponding AE signals. It was found that the proposed AE method was effective in detecting the debonding process between the FRP/steel bars and the hosting concrete. The AE signal strength exhibited a good correlation with the actual bond stress-slip relationship measured in each specimen. Based on the AE location technique, the invisible non-uniform distribution of bonding stress along the bar was further revealed, the initial location of damage and the debonding process were captured. Additionally, the contribution of bar-to-concrete load-bearing mechanism (chemical adhesion, friction, and mechanical interlocking) to sustain the pull-out force was effectively clarified by studying the collected signals in the frequency domain of AE methods. The experimental results demonstrate that the proposed AE method has potential to detect the debonding damage of FRP/steel bar reinforced SCC structures accurately.

A critical evaluation of tribological interaction for restorative materials in dentistry

Dental bio-tribology is a developing and promptly expending research field that develops an understanding for designing of dental implants and better selection of artificial dental material. Importance of tribology in modern restorative dentistry is significantly reviewed including synthetic teeth and dental implants. The wear characteristic is one of the extremely important parameters in demonstrating the clinical success of dental composite restoratives. Superior wear resistance of denture teeth conserves a good relationship of functional stability and harmonious occlusion. The usage of resin based dental composites has increased considerably in recent years. These composites have numerous advantages i.e. good esthetics, significant mechanical properties, potential to cohere to the tooth structure etc. Despite of these benefits tribological aspect of the restorative resin composites are still needing to be focused i.e. low wear resistance of material, especially for posterior teeth and increased wear rate of opposite teeth. The most common wear of dental composite consists of distinct phenomenon such as chemical degradation, abrasion, adhesion, attrition and fatigue. The aim of restorative dentistry is to develop highly wear resistant materials that do not cause wear of opposite tooth structure. This evaluation especially focuses on the investigation of the factors associated with inter-oral movements and mastication process along with the study of distinct wear mechanism, harsh intraoral environments, and effect of occlusal force on the friction and wear characteristics of human teeth. Moreover, this study also fortifies to the wear aspect of resin based dental composites as well as future developments of these materials are recommended from a tribological perspective. Additionally, in dental prosthodontics, the role of chewing motor regulation and periodontal mechanoreceptor responses in occlusal functions has been discussed and also the clinical significances of oral implants interactions in patients for fixed dental prostheses and some clinical case studies of the patients with the presence and absence of periodontal diseases are discussed thoroughly.

The Chemical Compatibility and Adhesion of Energetic Materials with Several Polymers and Binders: An Experimental Study.

The chemical compatibility and the adhesion of energetic materials and additive materials exert a strong influence on the sensitivity, safety and performance of a polymer-bonded explosive (PBX). In this study, the chemical compatibility of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), pentaerythritol tetranitrate (PETN) with several polymers were evaluated using the vacuum stability test (VST) and the differential scanning calorimetry (DSC); while the adhesion between RDX or PETN and each binder based on these polymers was determined through interfacial characteristics using contact angle measurement. The experimental results demonstrate that RDX and PETN are compatible with polystyrene (PS), nitrocellulose (NC) and fluoroelastomer (FKM) according to the STANAG 4147. Therefore the two polymers can be used as adhesives in PBX composition. Moreover, based on interfacial characteristics such as interfacial tension and work of adhesion, the adhesion between RDX and each binder was predicted to be better than that of PETN.

Facile Synthesis of rGO/g-C3N4/CNT Microspheres via an Ethanol-Assisted Spray-Drying Method for High-Performance Lithium-Sulfur Batteries.

rGO/g-C3N4 and rGO/g-C3N4/CNT microspheres are synthesized through the simple ethanol-assisted spray-drying method. The ethanol, as the additive, changes the structure of the rGO/g-C3N4 or rGO/g-C3N4/CNT composite from sheet clusters to regular microspheres. In the microspheres, the pores formed by reduced graphene oxide (rGO), g-C3N4, and carbon nanotube (CNT) stacking provide physical confinement for lithium polysulfides (LiPSs). In addition, enriched nitrogen (N) atoms of g-C3N4 offer strong chemical adhesion to anchor LiPSs. The dual immobilization mechanism can effectively alleviate the notorious "shuttle effect" of the lithium-sulfur battery. Meanwhile, the cathode with high cyclic stability can be achieved. The rGO/g-C3N4/CNT/S cathode delivers a discharge capacity of 620 mA h g-1 after 500 cycles with a low capacity fading rate of only 0.03% per cycle at 1 C. Even, the cathode shows a retained capacity of 712 mA h g-1 over 300 cycles with a high sulfur loading (4.2 mg cm-2) at 0.2 C.

Effectiveness of current adhesive systems when bonding to CAD/CAM indirect resin materials: A review of 32 publications.

SummaryThe purpose of this review was to assess the available literature regarding bonding between current adhesive systems and computer-aided design/computer-aided manufacturing (CAD/CAM) indirect resin materials, to provide clinicians with a comparative overview of the relevant bonding procedures. An electronic search was performed through PubMed based on the keywords CAD/CAM and dental bonding. Additional relevant literature was obtained from the citations in the articles. A total of 313 papers were identified, of which 281 were excluded as being unsuitable, and an additional 3 papers were identified, giving a total of 32 articles that are included in this review. Based on this survey, it is recommended that microretentive surfaces should be generated by either blasting or hydrofluoric acid etching. This initial process should be followed by silanization to ensure chemical adhesion prior to bonding to CAD/CAM indirect resin composite materials (including Lava Ultimet, KATANA AVENCIA block, Gradia Block, Cerasmart, Paradigm, and Block HC) and CAD/CAM polymer-infiltrated ceramics (such as Vita Enamic). The use of materials containing methyl methacrylate (MMA) also appears to improve the bonding of CAD/CAM poly(methyl methacrylate) (PMMA) resin materials (including XHIPC-CAD/CAM, artBloc Temp, and Telio).

CNT Interwoven Nitrogen and Oxygen Dual-Doped Porous Carbon Nanosheets as Free-Standing Electrodes for High-Performance Na-Se and K-Se Flexible Batteries.

Na-Se and K-Se batteries are attractive as a stationary energy storage system because of much abundant resources of Na and K in the Earth's crust. As the alloy-type Se has a severe pulverization issue, one critical challenge to develop advanced Na-Se and K-Se batteries is to explore a highly efficient and stable Se-based cathode. Herein, a flexible free-standing Se/carbon composite film is prepared by encapsulation of Se into a carbon nanotube (CNT) interwoven N,O dual-doped porous carbon nanosheet (Se@NOPC-CNT). The 3D interconnected CNT uniformly wrapped on the N,O dual-doped porous carbon skeletons improves the flexibility and offers an interconnected conductive pathway for rapid ionic/electronic transport. In addition, the N,O dual-doping significantly enhances the chemical affinity and adhesion between Nax Se/Kx Se (0 < x ≤ 2) and porous carbon, which is confirmed by density functional theory calculation. When used as the cathode in Na-Se batteries, the Se@NOPC-CNT delivers a remarkable reversible capacity of 400 mA h g-1 at 1 A g-1 after 2000 cycles with a 0.008% capacity decay per cycle. For K-Se batteries, it also exhibits an excellent cycling stability (335 mA h g-1 after 700 cycles at 0.8 A g-1 ). This unique design may open an avenue for practical application of flexible Na-Se and K-Se batteries.

The need for a concept of shape homeostasis

A major step forward for developmental biology will be accomplished when someone figures out how to extend the concept of homeostasis to apply to shapes, in the sense of geometric properties of cells, tissues and organs. I propose that the biggest obstacle to this forward step is that biological researchers are not yet familiar with the properties of tensor variables, as compared with scalars. This key difference is that tensor properties can and usually do have different amounts in different directions, whereas scalar properties cannot vary with direction. Examples of tensor variables include stress, strain, curvature, permeability, and stiffness. Examples of scalar properties include chemical concentrations, osmotic pressure, hydrostatic pressure, adhesiveness and electrical voltage. Even D'Arcy Thompson treated mechanical tension (which is the classic example of a tensor variable) as if it were a scalar constant. This greatly reduced the number of geometric shapes that he could explain as being directly produced by forces. For example, in order to generate cylinders, surface contractions need to be twice as strong in one direction as compared with the perpendicular direction. Unless surface contractions vary with direction, only spheres can be generated.Another example of not distinguishing tensors from scalars is the use of suction pipettes to measure stresses of cell surfaces (for example, during cytokinesis). This method of measurement inescapably lumps together directional components of two different tensors (tension and stiffness) as if they were one scalar. Yet another obstacle was that certain scientists argued persuasively, but mistakenly, that attractor basins were evidence of minimization of thermodynamic free energy.Chemical concentrations have no special ability to generate gradients. Neither do any other scalar variables. As will be discussed below, repeated local equilibration of any quantitative variable will generate at least as good a gradient as diffusion can. It is misguided to think of scalars as being in any sense more quantitative than tensors. In fact, tensor variables can convey more information than chemical gradients, often faster and with less vulnerability to disturbance.

The pull-out behavior of straight and hooked-end steel fiber from hybrid fiber reinforced cementitious composite: Experimental study and analytical modelling

This paper deals with the interfacial bonding performance of the steel fiber in the steel-polypropylene hybrid fiber reinforced cementitious composite. 42 groups of straight and hooked-end steel fiber specimens are investigated by the single-sided pull-out tests. The whole pull-out load-slip responses are captured, and the effects of hybrid fiber dosage, matrix strength and fiber embedded length are analyzed. Furthermore, the interfacial bonding mechanism and fiber reinforcing mechanism are revealed based on SEM images. Results show that the addition of hybrid fibers in the matrix contributes significantly to increasing the maximum and residual pull-out load as well as improving the pull-out energy dissipation capacity. The polypropylene fiber content is found to be the dominant factor for the variation of interfacial properties. For straight steel fiber, the enhancing effect of hybrid fiber on the chemical adhesion force is more pronounced than that on the sliding frictional force. For hooked-end steel fiber, the contribution of hybrid fiber is not significant on the hook mechanical interlocking. Finally, a theoretical model is developed to predict the pull-out behavior with the hybrid fiber effect taken into account. The predictions provide satisfactory correlation to the experimental results from both the current study and previous work.

Alkyds from red silk-cotton (Bombax ceiba) seed oil and investigation on their microbial degradation

The vegetable oils are being increasingly used for the synthesis of several types of polymers. In the present study red silk-cotton (Bombax ceiba) seed oil was used to synthesize alkyds which were characterized by Fourier transform infrared (FT-IR) and 1H nuclear magnetic resonance (NMR) spectroscopic studies. The physico-chemical properties such as colour, acid value, free fatty acid content and iodine value of the alkyds were evaluated. The coating performance of the cured films was tested by measuring chemical resistance, thermal stability, pencil hardness, gloss and adhesion. Subsequently microbial degradation studies of the alkyds were done using Pseudomonas aeruginosa (MTCC1934) and Bacillus subtilis (MTCC1305) strains and the results indicated substantial degradation in each case.

Synthesis of Polymeric Carbon Nitride Films with Adhesive Interfaces for Solar Water Splitting Devices

Polymeric carbon nitride (PCN) films are synthesized for solar water splitting devices. Herein, five precursors and their mixtures are attempted, achieving PCN films in ca. 40 different morphologies. We find that sulfur (S) containing and non-S precursors must be mixed to grow PCN films on fluorine doped tin oxide (FTO) glasses. Through the investigations of the PCN films, S is found to only exist at the interfaces between the PCN and FTO films. In this case, S acts not only as the initialization for the growth of the PCN films but also as connections to assist charge migration for water splitting devices. As a result, the best performance ca. 100 μA/cm2 is achieved at 1.23 VRHE under AM 1.5 illumination in NaOH electrolyte solution without sacrificial agent. This result can be attributed to the reduced defects along the interfaces and the lessened charge recombination. This synthesis of PCN films with the improved chemical adhesion to the FTO layer envisages such organic material for the construction of other flexible functional devices.

Which low-fusing porcelain glaze treatment technique is better to promote a vitreous surface on Y-TZP ceramic?

OBJECTIVE: to evaluated the influence of two types of low-fusing porcelain glaze application on the surface of a zirconia ceramics stabilized by yttrium (Y-TZP).METHODS: Y-TZP specimens were divided into five groups (n=5) according the surface treatments: control (CO), no treatment was performed; application of a thin low-fusing porcelain glass layer by the powder/liquid technique (GPL); GPL followed by 10% hydrofluoric acid (HF) etching (GPL-HF); glaze spray application (GS); GS followed by 10% HF etching (GS-HF). Roughness measurements contact angle, x-ray diffraction, energy-dispersive spectroscopy (EDS) and scanning electron microscope (SEM) analysis were performed.RESULTS: ANOVA and Tukey tests revealed that GPL had significantly lower contact angle values than the other groups (GPL:50.31º; GPL-HF: 72.73º; GS-HF: 81.73º; CO: 96.48º; GS:101.30º; p=0.001). GPL-HF presented a significant higher roughness (Ra/Rq: 2658.0/3367.0 ηm; p=0.001) than the other groups (GPL: 872.1/1162.0 ηm; GS-HF: 383.0/603.6 ηm; GS: 303.4/391.3 ηm; CO:263.4/339.1 ηm). The X-ray diffraction analysis just tetragonal phase in all groups. EDS and SEM analysis show a highest amount of silica on GPL and GPL-HF surface.CONCLUSION: the application of the low-fusing porcelain glaze by the powder/liquid technique followed by the HF etching promoted a better surface to micromechanical and chemical adhesion.

Two-year clinical performance of cast post and core self-adhesive cementation

Introduction and Objective: Endodontically treated teeth commonly present extensive tissue loss, requiring the use intraradicular posts, which provide retention for a coronal rehabilitation. Cast post and cores (CPCs) have been traditionally used in cases of marked tooth tissue loss. Case report: This case report describes two cast post and cores and subsequent rehabilitation by metal ceramic crowns. The patient was followed-up at intervals of 12 and 24 months after the rehabilitation. The posts were cemented within the root canal with self-adhesive resin cement, in a way that guarantees a perfect sealing of the root and remains stable in the oral environment. Conclusion: Self-adhesive cements are a one-step material capable of providing additional chemical adhesion to the metal, creating a monoblock, quality not found in conventional resin cements, where the adhesion occurs only in the dentin-cement interface.

Bioinspired Mineral-Organic Bioresorbable Bone Adhesive.

Bioresorbable bone adhesives have potential to revolutionize the clinical treatment of the human skeletal system, ranging from the fixation and osteointegration of permanent implants to the direct healing and fusion of bones without permanent fixation hardware. Despite an unmet need, there are currently no bone adhesives in clinical use that provide a strong enough bond to wet bone while possessing good osteointegration and bioresorbability. Inspired by the sandcastle worm that creates a protective tubular shell around its body using a proteinaceous adhesive, a novel bone adhesive is introduced, based on tetracalcium phosphate and phosphoserine, that cures in minutes in an aqueous environment and provides high bone-to-bone adhesive strength. The new material is measured to be 10 times more adhesive than bioresorbable calcium phosphate cement and 7.5 times more adhesive than non-resorbable poly(methyl methacrylate) bone cement, both of which are standard of care in the clinic today. The bone adhesive also demonstrates chemical adhesion to titanium approximately twice that of its adhesion to bone, unlocking the potential for adherence to metallic implants during surrounding bony incorporation. Finally, the bone adhesive is shown to demonstrate osteointegration and bioresorbability over a 52-week period in a critically sized distal femur defect in rabbits.

Effect of Maximum Aggregate Size on the Bond Strength of Reinforcements in Concrete

The bond between reinforcements and concrete is the only mechanism that transfers the tensile stresses from concrete to reinforcements. Several factors including chemical adhesion, roughness and reinforcement interface and bar bearing affect the bond strength of reinforcements with concrete. This work was carried out considering another varying factor which is maximum aggregate size. Four mixes of concrete with similar compressive strengths but different maximum aggregate sizes of 25.4mm, 19.05mm, 12.7mm and 9.53mm were used with the same bar size of 16mm. Compressive strength, splitting tensile strength and bond strength for each concrete mix were studied. Test results depict a slight increase in compressive and splitting tensile strength with decrease in maximum aggregate size. The bond strength remained at the same level with decrease in maximum aggregate size except at maximum aggregate size of 9.53mm when there was a drop in bond strength, despite better compressive and splitting tensile strengths. ACI-318 and FIB-2010 codes equation for bond strength calculation work well only when the maximum aggregate size is 12.7mm and above. Therefore, maximum aggregate size is critical for bond strength when smaller size aggregates are used.

Optimization of mechanical and tribological properties of carbon fabric/resin composites via controlling ZnO nanorods morphology

The multi-scale reinforcements of ZnO nanorods/carbon fabric with different morphologies were obtained using a simple water bath method via controlling the concentration of growth solution for a new application in wet friction materials. The ZnO nanorods/carbon fabric were characterized via X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectra. As a result, the ZnO nanorods/carbon fabric/resin composite (sample CP3) possesses the maximum bending and tensile strength of 62.7 MPa and 170.0 MPa, which increases by 40.2% and 59.1% compared with that of bare carbon fabric/resin composite due to the best mechanical interlocking and chemical adhesion at the interfacial region of the composite. Meanwhile, the wear rate of the sample CP3 decreases obviously by 81.5% together with stable friction coefficient under various friction condition. From view point of material design, it is necessary to control the morphologies of ZnO nanorods to optimize mechanical and tribological properties of ZnO nanorods/carbon fabric/resin composites.