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Anaerobic adhesives (AAs) cure at room temperature in oxygen-deprived spaces between metal substrates. The curing process is significantly influenced by the type of metal ions present. This study investigates the curing kinetics of a high-strength AA on iron and copper substrates using differential scanning calorimetry (DSC). The activation energy and kinetic parameters were determined with different empiric models, revealing that curing on copper is faster and more complete compared to iron. The findings suggest that copper ions lower the activation energy required for curing, enhancing the adhesive's performance. This research addresses the gap in understanding how metal ions affect AA curing kinetics, offering valuable insights for optimizing adhesive formulations for industrial applications. [ABSTRACT FROM AUTHOR]

Anaerobic adhesives (AAs) cure at room temperature in oxygen-deprived spaces between metal substrates. The curing process is significantly influenced by the type of metal ions present. This study investigates the curing kinetics of a high-strength AA on iron and copper substrates using differential scanning calorimetry (DSC). The activation energy and kinetic parameters were determined with different empiric models, revealing that curing on copper is faster and more complete compared to iron. The findings suggest that copper ions lower the activation energy required for curing, enhancing the adhesive’s performance. This research addresses the gap in understanding how metal ions affect AA curing kinetics, offering valuable insights for optimizing adhesive formulations for industrial applications.

This scientific study aims to validate the applicability of a micromechanical model for predicting the static shear strength of hybrid interfaces that are pressure-reinforced and bonded with anaerobic adhesives. To identify the parameters for the micromechanical model, a systematic experimental test plan involving high-strength steel butt specimens bonded with anaerobic adhesive in a finite thickness was performed. The experimental investigation was based on torque tests, which provided the shear strength of two anaerobic adhesives subjected to different values of contact pressure, ranging from 0 up to 1000 MPa. Based on the intrinsic high-pressure properties of the finite-layer adhesives, the formerly developed micromechanical model of hybrid interfaces satisfactorily predicted the macroscopic strength of tightened-bonded joints taken from the literature. [ABSTRACT FROM AUTHOR]

This scientific study aims to validate the applicability of a micromechanical model for predicting the static shear strength of hybrid interfaces that are pressure-reinforced and bonded with anaerobic adhesives. To identify the parameters for the micromechanical model, a systematic experimental test plan involving high-strength steel butt specimens bonded with anaerobic adhesive in a finite thickness was performed. The experimental investigation was based on torque tests, which provided the shear strength of two anaerobic adhesives subjected to different values of contact pressure, ranging from 0 up to 1000 MPa. Based on the intrinsic high-pressure properties of the finite-layer adhesives, the formerly developed micromechanical model of hybrid interfaces satisfactorily predicted the macroscopic strength of tightened-bonded joints taken from the literature.

Although anaerobic adhesives are extensively used in addition to mechanical tightening in flanged couplings, interference fits, and threaded connections, their constitutive behaviour still needs to be investigated. According to the micromechanical model proposed by Dragoni and Mauri [Proc. of the IMECHE Part L J. of Mat.: Des. and Appl. 2002; 216: 9–15], the shear strength of the anaerobic adhesives significantly improves with the contact pressure applied to the thin adhesive layer. In order to assess this hypothesis, this work investigates the shear strength of an anaerobic adhesive layer with finite thickness and surface area, subject to a nearly-uniform contact pressure, up to 1000 MPa. The tests involved a head to head bonded specimen, made of high strength steel adherends (39NiCrMo3), with a controlled roughness on the bonding surfaces. Both a weak and a strong anaerobic adhesive (Loctite 243 and Loctite 638) are investigated. A full-field technique, such as the Digital Image Correlation, was used in order to detect the 3D displacement and strain fields, and to evaluate the twist angle of the entire external surface, with particular attention to the interface area. The preliminary results prove the reliability of the test bench and confirms the piezo-resistive response of the anaerobic adhesive. [ABSTRACT FROM AUTHOR]

Understanding the locus of fluid flow along thrust and splay faults is important to understand the hydraulic properties of accretionary systems and fault mechanics. Here, we use rock magnetic techniques in combination with backscattered electron imaging to depict the locus of enhanced magnetic mineral alteration within the Pāpaku fault, an active splay fault of the subduction interface at the northern Hikurangi Margin. The Pāpaku fault was cored at Site U1518 during Expedition 375 of the International Ocean Discovery Program and we report room temperature magnetic parameters, complemented by first‐order reversal and thermomagnetic curves in the depth interval 250–400 m below seafloor (mbsf). The ∼60‐m wide Pāpaku fault zone comprises two main slip zones, referred to as the upper main brittle (304–321 mbsf) and lower subsidiary (351–361 mbsf) fault zones, and an intervening zoned, termed the lower ductile deformation zone. Two narrow zones, at the top of the main brittle fault zone, and one in a sand‐rich interval above the subsidiary fault zone, experienced enhanced magnetic mineral diagenesis, which resulted in the recrystallization of ferrimagnetic greigite to paramagnetic pyrite. We propose that secondary magnetic mineral diagenesis was driven by anaerobic methane oxidation within these intervals, which occurs in the presence of methane and sulfate. We relate the observed changes to the fault parallel transport of fluids which is restricted to two damage zones. Overlying compacted and clay‐rich sediments likely act as a barrier to upward advective flow through the fault zone and into the hanging wall. Key Points: We report the results of rock magnetic properties and backscattered electron investigations in a profile through a subduction splay faultEnhanced magnetic mineral diagenesis in two slip zones resulted in the neoformation of iron‐sulfide mineralsWe suggest that the accumulation and fault parallel transport of reactants in fracture zones allowed anaerobic methane oxidation to occur [ABSTRACT FROM AUTHOR]

Measuring the nitrogen isotope compositions (δ15N) of nitric oxide (NO) from different sources helps to quantify the relative contributions of atmospheric NOx. Soil is one of the most important sources of atmospheric NOx, but only limited measurements on the δ15N of soil‐emitted NO exist, hampering our ability to partition sources to air pollution. Here we conducted soil incubations to measure the δ15N‐NO under defined aerobic or anaerobic conditions, favoring either nitrification or denitrification. Soils were collected from seven sites spanning three ecosystems in northern China (two agricultural, two forest, and three grassland sites). We found that the δ15N‐NO and their associated N isotope fractionations were significantly different between anaerobic and aerobic conditions in seven soils. Under aerobic condition, the δ15N‐NO ranged from −62‰ to −50‰ (averaged −56 ± 4‰), being significantly more negative (by 23‰) than those under anaerobic condition (−45‰ to −23‰, averaged −33 ± 7‰). The apparent N isotope fractionation for NO production under aerobic condition (15εaerobic = 61 ± 3‰) was significantly higher (by 26‰) than under anaerobic condition (15εanaerobic = 35 ± 6‰), with a small variability among ecosystem types. Our study demonstrates that the δ15N‐NO from different soils are very different from fuel combustions (mainly from 0‰ to +20‰), supporting that measuring 15N is a useful tool to partition the contributions of soil NO to atmospheric NOx. Our results also imply δ15N‐NO produced by nitrification and denitrification distinctly different, as these two processes are dominant processes producing NO under aerobic and anaerobic conditions, respectively. Plain Language Summary: Nitric oxide (NO) affects the atmosphere chemistry and NO itself a key component of air pollution and a precursor to other air pollutants like particulate matter and ozone. To reduce the air pollution, it is crucial to identify the atmospheric NO sources. Measuring 15N natural abundance has been considered as a promising tool to identify different sources, but the measurement on δ15N for soil‐emitted NO is limited, adding to the large uncertainties on NO partitioning. Here we measured the δ15N‐NO emitted from three ecosystem types across seven sites (two agriculture, two forest, and three grassland sites) under defined anaerobic or aerobic conditions. We found that soil‐emitted NO was 15N‐depleted (−62‰ to −23‰) related to the source from fossil fuel combustion (0–20‰), suggesting that δ15N can be used to separate these two sources. We also found that the δ15N‐NO under aerobic condition (nitrification prevailing, −62‰ to −50‰) was much lower than under anaerobic condition (denitrification prevailing, −45‰ to −23‰), which provide a useful tool to better understand the relative contributions of different sources of NO. In sum, soil‐emitted NO has their own different isotope fingerprint, depending on the soil oxygen conditions, and can be used to partition sources. Key Points: The δ15N‐NO from soil (−62‰ to −23‰) is different from fuel combustion (0‰ to 20‰), allowing effective source partitionThe δ15N‐NO produced under aerobic condition (favor nitrification) was more negative than under anaerobic condition (favor denitrification)The 15ε for NO production under aerobic condition (61 ± 3‰) was significantly higher than under anaerobic condition (35 ± 6‰) [ABSTRACT FROM AUTHOR]

The paper deals with the experimental measurement of the shear strength in hybrid interfaces, press fitted and bonded with anaerobic adhesives. The aim is to validate and improve the applicability of a constitutive model, which describes the interface behavior up to complete failure, by combining a cohesive law with a pure friction law. This paper presents an extensive experimental test plan, which deeply investigates the shear strength of two strong anaerobic adhesives, over four nominal contact pressure levels. The tests involve cylindrical specimens, butt bonded and pressure reinforced over an annular surface, and seven replications, giving 56 tests. The experimental torque-rotation curves up to complete failure highlight a similar response between the two adhesives, and confirm that the strain energy up to complete failure sums up a cohesive term and a pure friction term. In addition, the main parameters of the model linearly depend from contact pressure through simple relationships. [ABSTRACT FROM AUTHOR]

To improve the heat-resistance of anaerobic adhesives, a borosiloxane oligomer (BSi) was directly synthesized by the co-condensation of boric acid with phenyl triethoxysilane without any external addition of water, catalyst or solvent. The BSi-modified anaerobic adhesive based on ethoxylated bisphenol A dimethacrylate was prepared. The above-prepared BSi was characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The effects of BSi modification on the bonding strength of the anaerobic adhesives were investigated using dynamic mechanical analysis (DMA), TGA, scanning electron microscopy (SEM), FTIR and strength testing. The curing behavior was evaluated using differential scanning calorimetry (DSC) analysis. The results showed that the BSi-modified anaerobic adhesive exhibited an increase in the bonding strength at room temperature. The bonding strength decreased as the testing temperature increased. However, the BSi polyblended adhesive showed a significant enhancement in the bonding strength at 400 °C because of the further formation of a Si-O-B crosslinked structure. BSi can be used as a potential heat-resistant additive that is available for threadlocking and retaining applications at 400 °C; in addition, the curing reaction of anaerobic adhesives can be promoted using BSi. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is the slowest process in municipal wastewater treatment, requiring at least 15 days of SRT (solids retention time). Here, we implemented microbial electrolysis cells (MECs) in anaerobic digesters to shorten the long SRT requirement. The MEC bioanode oxidizes acetic acid while the cathode produces H2 gas. The electrode reactions can expedite acetic acid decomposition and thus enhance the rate of biosolids destruction because acetoclastic methanogenesis is known to be the rate-limiting step in conventional anaerobic digestion. A lab-scale electrically-assisted digester (EAD) with the MEC reactions was operated under a continuous fed-batch mode using raw wastewater sludge. Additionally, a steady-state model was developed by incorporating the MEC reaction in ADM1 (Anaerobic Digestion Model No.1 by International Water Association). In experiments, the EAD achieved 55% VSS (volatile suspended solids) removal and 61% COD (chemical oxygen demand) removal at a 6-day SRT while the control digester (built with the same electrode components but no MEC reactions induced) showed only 47% VSS removal and 50% COD removal. This result indicates that the SRT requirement can be substantially reduced by implementing the MEC reactions in mesophilic anaerobic digestion. Under a 14-day or 2-day SRT condition, however, the EAD did not show meaningful improvements on the COD and VSS removal compared to the control digester. Hydrogenotrophic methanogenesis was sufficiently rapid as H2 gas was not detected in produced biogas. The mathematical simulation results demonstrated that the MEC reactions substantially reduce acetic acid concentration and thus supplement the slow acetoclastic methanogenesis reaction. [ABSTRACT FROM AUTHOR]

The paper experimentally investigates hybrid interfaces pressure-reinforced and bonded with anaerobic adhesive. While their static strength has been deeply investigated, their behavior up to complete failure lacks of a constitutive model. This work aims to assess the applicability of a simple model involving a cohesive law and a pure friction law, in order to describe the interface behavior up to complete failure under different contact pressure levels. A systematic experimental campaign investigates the shear strength of cylindrical specimens butt-bonded and pressure reinforced over an annular surface. The tests involve two anaerobic adhesives and four pressure levels. The experimental torque-rotation curves confirm that the strain energy up to complete failure is given by a cohesive term and a pure friction term, both of them linearly dependent upon the contact pressure. [ABSTRACT FROM PUBLISHER]

Anaerobic adhesives are polymerized and hardened rapidly through a free radical mechanism when placed between two metallic surfaces. The conducted investigations from 1960 have studied polymerization rate in the presence of different metallic ions, their breakdown speed using polarography techniques, and also the common use of cumene hydro-peroxide as an initiator. In order to investigate the effect of initiator type and concentration on the setting time of these adhesives, four different types of initiators in concentrations of 1–3 parts per hundred resin (phr) were incorporated into the monomer. The initiators were cumene hydroperoxide (CHP), methyl ethyl ketone peroxide, tert-butyl hydroperoxide, and benzoyl peroxide. The metal salt used was copper (II) saccharin. The obtained results indicated that the setting time in the methacrylate compositions depends not only on the initiator concentration, but also on its relative amount with respect to the metal ion, and some other factors such as monomer type, and stoichiometric relation between the metal ion and the accelerator—here, dimethyl p-toluidine, which was assumed to have an important role in the setting process. Finally, CHP was identified as the most appropriate initiator with an optimum value of 2 phr. [ABSTRACT FROM PUBLISHER]

The aim of this study was to evaluate the use of γ-methacriloxypropyltrimethoxysilane (MPS) to promote the adhesion of electrogalvanized steel sheets and threaded joints when an anaerobic adhesive is selected. The influence of the pH of the silane solution on the coupling agent properties of MPS coatings was evaluated preparing two silane aqueous solutions at 1% volume of silane and two different values of pH (4 and 6). Those coatings were characterized in terms of infrared spectroscopy (FTIR), scanning electronic microscopy (SEM), contact angle and surface energy. The influence of pretreatment conditions on the adhesive performance of steels was then evaluated both by shear tests from single lap adhesive joints and screw–nut bonds. Results show that the use of coatings hydrolyzed at pH 4 exhibit better adhesion behavior than those hydrolyzed at pH 6. The shear strength of anaerobic adhesive joints dramatically increases, showing a cohesive failure. This is related to the hydrolysis and condensation rates of silane solution and the stability of the metallic surface in contact with silane solution at the studied pH values. [ABSTRACT FROM AUTHOR]

This paper presents results from tests to assess the use of anaerobic adhesive for providing a prevailing torque locking feature in threaded fasteners. Test procedures are developed and tests are performed on three fastener materials, four anaerobic adhesives, and both seated and unseated assembly conditions. Five to ten samples are tested for each combination. Tests for initial use, reuse without additional adhesive, and reuse with additional adhesive are performed for all samples. A 48 h cure time was used for all initial use and reuse tests. Test data are presented as removal torque versus removal angle with the specification required prevailing torque range added for performance assessment. Percent specification pass rates for all combinations of fastener material, adhesive, and assembly condition are tabulated and reveal use of anaerobic adhesive as a prevailing torque locking feature is viable. Although not every possible fastener material and anaerobic adhesive combination provides prevailing torque values within specification, any combination can be assessed using the test procedures presented. Reuse without additional anaerobic adhesive generally provides some prevailing torque, and in some cases within specification. Reuse with additional adhesive often provides comparable removal torque data as in initial use. [ABSTRACT FROM AUTHOR]

Studies concerning the development of UV-curable anaerobic compositions have been conducted. The influence of oligo(urethane acrylates) (OUAs), monomer-diluents, cross-linking agents, and photoinitiators (PIs) on the parameters of the photocuring and properties of adhesive compositions has been examined. Stable, fast-curing anaerobic adhesives capable of photocuring have been developed. [ABSTRACT FROM AUTHOR]

Abstract: Press fitted and adhesively bonded joints give several advantages: among others, they lead to smaller constructions for a given load capacity, or to stronger constructions for a given size. For that reason, the static and fatigue strength properties of these joints have been studied extensively. Studies dealing with the influence of the engagement ratio (i. e. the coupling length over the coupling diameter) are still limited. This work aims at filling the gap, limited to the case of a single component anaerobic adhesive. Coupling and decoupling tests have been performed both on press-fitted and adhesively bonded specimens and on pin–collar samples, considering four different levels for the engagement ratio. The study shows that the engagement ratio has a negligible effect on the shear strength of the adhesive and also on the relationship between the decoupling and the coupling forces. Moreover, the obtained results show that a too high interference level in press-fitted and adhesively bonded joints may have a detrimental effect on the adhesive strength. [Copyright &y& Elsevier]

Abstract: Anaerobic adhesives are commonly used to enhance the shear strength of clamped friction joints between metal parts. Experimental results show that the total strength of the friction-bonded interface steadily increases with the clamping pressure. However, if weak anaerobics are used in the assembly, its strength is lower than the dry (purely friction) joint's under high applied pressures. This paper seeks an explanation for this macroscopic behaviour by means of microscale finite-element simulations. The analyses show that the experimental results can be explained by assuming that: (a) however great the clamping pressure, a thin film of adhesive remains trapped between the crests of the mating surfaces; (b) under the high local pressure the shear strength of this film becomes greater than the regular adhesive at no pressure; (c) the stronger adhesives entail a higher increase than the weaker adhesives. [Copyright &y& Elsevier]

This studywas performed to investigate the influence of operational pH on dark H2 fermentation of food waste by employing anaerobic batch reactors. The highest maximum H2 yield was 1.63 mol H2/mol hexoseadded at operational pH 5.3, whereas the lowest maximum H2 yield was 0.88 mol H2/mol hexoseadded at operational pH 7.0. With decreasing operational pH values, the n-butyrate concentration tended to increase and the acetate concentration tended to decrease. The highest hydrogen conversion efficiency of 11.3% was obtained at operational pH 5.3, which was higher than that (8.3%) reported by a previous study (Kim et al. (2011) 'Effect of initial pH independent of operational pH on hydrogen fermentation of foodwaste', Bioresource Technology 102 (18), 8646-8652). The newresult indicates that the dark fermentation of food waste was stable and efficient in this study. Fluorescence in situ hybridization (FISH) analysis showed that Clostridium species Cluster I accounted for 84.7 and 13.3% of total bacteria at operational pH 5.3 and pH 7.0, respectively, after 48 h operation. [ABSTRACT FROM AUTHOR]

Many proteins use corrinoid cofactors to facilitate methyl transfer reactions. Recently, a corrinoid protein, HgcA, has been shown to be required for the production of the neurotoxin methylraercury by anaerobic bacteria. A strictly conserved Cys residue in HgcA was predicted to be a lower-axial ligand to Co(III), which has never been observed in a corrinoid protein. Here, we use density functional theory to study homolytic and heterolytic Co--C bond dissociation and methyl transfer to Hg(II) substrates with model methylcobalamin complexes containing a lower-axial Cys or His ligand to cobalt, the latter of which is commonly found in other corrinoid proteins. We find that Cys thiolate coordination to Co facilitates both methyl radical and methyl carbanion transfer to Hg(II) substrates, but carbanion transfer is more favorable overall in the condensed phase. Thus, our findings are consistent with HgcA representing a new class of corrinoid protein capable of transferring methyl groups to electrophilic substrates. [ABSTRACT FROM AUTHOR]

Highlights: [•] Under oxygen supply conditions, steel developed iron oxide surface deposits. [•] Sequential aerobic–anaerobic conditions lead to the formation of protective layer. [•] Under direct anaerobic conditions, the mackinawite corrosion layer was less protective. [•] The corrosion rate depends on the structural properties of the corrosion products. [ABSTRACT FROM AUTHOR]

The possibility of enhancing the heat resistance of acrylic anaerobic adhesives by introducing maleic acid imides was examined. The influence of the structure of the maleimides on the heat resistance of the compounds was studied. It was demonstrated by the example of the maleimide-diethylene glycol monomethyl ether methacrylate pair that imides are capable of copolymerization with acrylic monomers under the conditions of anaerobic curing at 25°C. [ABSTRACT FROM AUTHOR]

Anaerobic adhesives are thermosetting acrylic polymers commonly used to improve the performance of most metal joints. Researches on the static strength of hybrid joints, available in the technical literature, show scanty and contradictory results that do not explain the effect of anaerobic adhesive on the hybrid joint behaviour. An early study by one of the authors of the present study formulates a micro-mechanical model describing the shear power of anaerobic adhesives as a function of the intimate properties of adherends and adhesive at the interface. According to the micro-mechanical model, the high local pressure acting on the thin film of adhesive trapped between the crests of the mating surfaces improves the film shear strength upon the adhesive's shear strength at zero pressure. The present work aims to assess this micro-mechanical model through a systematic experimental campaign. The tests are conducted on simple tubular specimens and consider three variables over two levels: adhesive-type (weak and strong anaerobic), pressure level during polymerization (0.5 and 134 MPa), and pressure level during failure test (0.5 and 134 MPa). The results confirm the proposed micro-mechanical model, and highlight that shear strength slightly differs by applying pressure before or after polymerization. [ABSTRACT FROM PUBLISHER]

Abstract: Interference fitted and adhesively bonded joints, also known as hybrid joints, are an effective means to increase the transferable load while reducing both the weight and the stress level of the joined components. Many researches evaluated the strength of hybrid joints in dependence of several variables, such as the assembly pressure level, the type of materials in contact, the curing methodology, the operating temperature, and the loading type. To the authors' best knowledge, no data are available about the influence of the assembly technique on the shear strength of hybrid joints. This paper aims at filling the gap, by comparing the shear strength of hybrid joints realized by ‘press fitting’, by ‘shrink fitting’ and by ‘cryogenic fitting’. [Copyright &y& Elsevier]

Abstract: Anaerobic adhesives are commonly used to enhance the shear strength of clamped friction joints between metal parts. Experimental results show that the total strength of the friction-bonded interface steadily increases with the clamping pressure. However, if weak anaerobics are used, the combined strength is lower than in the dry (purely friction) joint under high applied pressures. This paper seeks an explanation for this macroscopic behaviour by means of microscale finite-element simulations. The analyses show that the experimental results can be explained by assuming that: (a) however great the clamping pressure, a thin film of adhesive remains trapped between the crests of the mating surfaces; (b) under the high local pressure the shear strength of this film is greater than the regular adhesive’s at no pressure; (c) the stronger adhesives entail a higher increase than the weaker adhesives. [Copyright &y& Elsevier]

Abstract: The main aim of this work is to study the influence of the geometry of screws on torsion tests when they are retained with adhesives. The geometry of different types of screw threads has been studied, measuring theoretical and real length values to determine the stress undergone by the thread when tightened and/or retained by anaerobic adhesives. Three kinds of joints are subjected to a torsion test to determine their loosening torque. According to their torque, joint loosening load as well as generated stress can be calculated. When tightened, the real contact area is observed to be lower than the theoretical area, and real stresses are therefore higher than the theoretical ones. The same can be observed when only adhesive is applied; the real bonded area is lower than the theoretical, while higher real stresses than theoretical are observed. When adhesive and tightening are combined, the stress due to the influence of the adhesive is calculated, since the strength ratio attributable to either friction or adhesion remains unknown. These can only be determined through the measurement of real thread dimensions. [Copyright &y& Elsevier]

A minimum hydrolysis time is required to get an adequate crosslinking between a silane film and a metallic substrate and that depends on the contents of silane, ethanol, and water in the silane solution. The objectives for this work are: 1) to study the effect of different ratios of ethanol/water on the hydrolysis time for a 1% bis-sulfur silane solution at pH 6, by attenuated total reflectance infrared spectroscopy. The different solutions studied correspond to different ratios of silane/ethanol/water by volume. The study was done following appearance of the siloxane and silanol groups and the disappearance of the ethoxysilane groups. 2) Also studied was the adhesion and corrosion behaviour of bis-sulfur silane (bis[3-(bis[3-(triethoxysilyl)propyl]disulfide, DS) in solutions of ethanol/water at pH 4 and 6 and γ-methacryloxypropyltrimethoxysilane (MPS) coatings obtained by a two-step process on galvanized steel samples. This coated surface was analysed by reflection absorption infrared spectroscopy (FTIR-RA), scanning electron miscroscopy (SEM), and polarization curves. Results obtained at pH 6 were compared with the ones for pH 4. Single lap shear tests were used to contrast the behaviour of anaerobic adhesives on electrogalvanized steel silanized samples. It was observed that higher hydrolysis time was necessary to get good adhesion behaviour if the solution was prepared at pH 4, while at pH 6 the best behaviour was observed for short hydrolysis times. [ABSTRACT FROM AUTHOR]

Possible interactions between the components of the anaerobic adhesive materials for their production, storage, and curing are considered based on the literature and experimental data. [ABSTRACT FROM AUTHOR]

Anaerobic adhesives have found an extensive use in many applications in mechanical engineering as sealers, threadlockers and retainers on metal surfaces. These adhesives have shown a good performance with threaded components with Cr[VI] coatings. Hexavalent chromium is a carcinogenic material so its use is limited or prohibited by environmental regulations in several countries, such as the United States and the European Union. In order to avoid this problem, non-chromated zinc coatings are used. However, anaerobic adhesives are not very effective with these types of coatings. Silane coupling agents could be an alternative to improve the performance of these coatings with anaerobic adhesives. The aim of this work was to investigate the effect of a silane treatment on Zn-electrocoated steel. H1-NMR (proton nuclear magnetic resonance) studies of γ-methacryloxypropyltrimethoxysilane (MPS) hydrolysis provide the optimal conditions for silane application onto substrates. Analysis of silane layers over zinc coatings was performed by means of Fourier Transform Infrared (FT-IR) spectroscopy. In addition, single lap shear tests were used to compare the strength of anaerobic adhesive joints on Zn-coated specimens with different surface treatments. NMR shows that maximum hydrolysis of MPS takes place at 150 min. Adhesive joints prepared using MPS coatings after this hydrolysis time give maximum shear strength. [ABSTRACT FROM AUTHOR]

The Conconi Threshold is a non-invasive method commonly used to predict the anaerobic threshold and also to apply specific and individual training intensities. However, the physiological mechanisms involved at the point in which the increase of heart rate becomes nonlinear even with workload increase is not clear. At the same way, its validity to predict metabolic transition thresholds and its reproducibility seems to be dependent of some others variables as the testing protocol. This review aims to put in evidence the physiological responses related to heart rate performance curve and the methodological aspects of the testing protocol that probably influence the phenomena. For this, it was used references of the national and international literature, either the most classical and most recent at the Medline data base. [ABSTRACT FROM AUTHOR]

A statistical method to study the reliability of cylindrical anaerobic adhesively-bonded assemblies is presented in this work. An anaerobic adhesive was used to manufacture four groups of bonds with different gaps, but with the same surface pre-treatment and curing position. Shear strength values were obtained and used to determine reliability of all adhesive bonds using the Weibull statistical distribution. Although the Weibull analysis has been widely used in the study of composite materials, its application in adhesive bonds is being explored now. A two-parameter Weibull distribution was employed to execute the Weibull analysis, using an estimator that renders a more realistic Weibull modulus value, as other estimators were found to subestimate or overestimate this value. Weibull modulus values were obtained for adhesive bonds with different gaps to study their reliability, and these results have been compared with the shear strength results. [ABSTRACT FROM AUTHOR]

The main objective of this research was a statistical study of pin-and-collar joints bonded with anaerobic adhesives. Surfaces were prepared in two different ways (by etching and abrading) prior to adhesive bonding. Moreover, samples were cured in two positions (vertical and horizontal) to study its influence. The effects of all these parameters have been analyzed through shear strength measurements. In order to carry out this study, statistical tools based on hypothesis contrast have been used. The results show that, in the studied materials, abrasion of surfaces prior to bonding promotes better mechanical strength than etching. Moreover, curing position has no statistical influence on mechanical properties in samples with a gap of 10 μm between adherends. [ABSTRACT FROM AUTHOR]

In a previous paper, the influence of the two typical major components of anaerobics (fumarate-based thickeners and low-molecular-weight poly(ethylene glycol) dimethacrylate monomers) on the blend rheology was studied. The blends obtained showed pseudoplastic behavior, and their viscosity at room temperature was established using the Cross equation as a function of the composition and the shear rate. In addition, the evolution of the zero shear rate viscosity as a function of the thickener weight fraction was studied, and it was shown that two critical concentrations were present. This work has focused on three-component formulations, based on the two previous components plus a thixotropic agent; fumed silica. Various fumed silicas were evaluated and they showed a significant effect on the blend pseudoplasticity even at low concentrations. In addition, the mixtures showed both the Bingham effect and thixotropy. These formulations were modeled using non-phenomenological equations. Finally, a method based on the previous models has been proposed to estimate the flow behavior in actual dispensing equipments. [ABSTRACT FROM AUTHOR]

Summary: Objectives: The two objectives of this experiment were to determine the surface temperature of enamel following acid etching, rinsing and drying, and to see whether two commercially available orthodontic brackets could be bonded to enamel using an anaerobic adhesive. Methods: Enamel surface temperature was determined in vivo using a surface temperature probe on a total of 60 patients. Stainless steel orthodontic brackets were bonded to human enamel using an anaerobic adhesive and a control orthodontic adhesive. The enamel was etched prior to bonding either with a solution of 37% o-phosphoric acid or, in the case of the anaerobic adhesive specimens, with a solution of 37% o-phosphoric acid containing copper (II) chloride. After bench curing the specimens were shear bond tested to failure and the load at debond recorded in each case. Results: The bond test results were analyzed using median force to debond (N) and 95% confidence intervals, Kaplan–Meier survival probabilities and log-rank tests. Conclusions: After etching rinsing and drying the enamel surface temperature ranged from 21.54 to 24.19°C, which is within the range suitable for anaerobic adhesive use. Bond testing to failure demonstrated that bracket base design affected the measured force to debond with both the anaerobic adhesive under test and the control adhesive. In addition, the anaerobic adhesive was affected by the material composition of the bracket base and curing time. After 1h of curing and using the Miniature Twin bracket, the measured force to debond exceeded the 10min force to debond results of the control adhesive. Significance: It is possible to bond commercially available orthodontic brackets to teeth using an anaerobic adhesive. [Copyright &y& Elsevier]

Objectives. The objectives of this experiment were to determine whether the incorporation of a surfactant into a combined etchant and activator solution would further promote the polymerization of an anaerobic adhesive.Method. Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case the enamel was etched and activated using a solution of 37% o-phosphoric acid containing copper (II) sulphates or chlorides with one of three surfactants also within the solution. After bench curing, the specimens were shear bond tested to failure and the load at debond recorded in each case.Results. The results were analysed using Kaplan–Meier survival probabilities and log-rank tests along with a multiple comparison test, using Bonferroni''s method.Conclusions. Under the conditions of this experiment the addition of a surfactant to a combined etchant activator solution of 37% o-phosphoric acid and either copper (II) sulphate or copper (II) chloride, prior to the use of an anaerobic adhesive can have a significant effect on measured force to debond. However, with copper (II) sulphate the highest force to debond was observed with the control solution without a surfactant. With copper (II) chloride the surfactant Tween 20 increased the observed force to debond but the effect was not statistically significant.Significance. Although it is possible to render the enamel surface both retentive and active towards anaerobic adhesives using a combined etchant and activator solution, the addition of a surfactant has little or no beneficial effect. [Copyright &y& Elsevier]

A study is done on the influence of fumarate-based thickeners on the rheological behavior of low-molecular-weight poly(ethylene glycol) dimethacrylate monomers diluents, often used as major components in the formulation of anaerobic adhesives. These solutions generally showed pseudoplastic behavior. The Cross equation was selected to determine the viscosity vs. shear rate curves, at constant temperature. The final equation relates the viscosity as a function of shear rate and thickener concentration. In addition, the zero shear rate viscosity evolution as a function of the thickener weight fraction was studied, showing that two critical concentrations were present. [ABSTRACT FROM AUTHOR]

This article compares the static strength and the fatigue strength (under repeated stress) of axially loaded taper press fits, either dry or bonded with an anaerobic adhesive. A general increase of both static and fatigue strength with the contact pressure is observed, the strength buildup being greater for the dry joints than for the bonded ones. No significant difference between the static and the fatigue strength is measured for the dry joints. For the bonded joints, the fatigue strength decay is nearly independent (in absolute terms) of the assembly contact pressure. [ABSTRACT FROM AUTHOR]

Objectives. The objectives of this experiment were to determine whether various transition metal salts in 37% o-phosphoric acid could both activate and etch an enamel surface prior to the use of an anaerobic adhesive.Method. Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case, the enamel was etched and activated using a solution of 37% o-phosphoric acid containing various transition metal sulfates and chlorides. After bench curing, the specimens were shear bond tested to failure and the load at debond recorded in each case.Results. The results were analyzed using mean force to debond (N) and 95% confidence intervals. Kaplan–Meier survival probabilities and log-rank tests were also performed.Conclusions. Under the conditions of this experiment, the sulfate and chloride of copper in acid were the most effective etching/activating solutions. There was no significant difference in the mean force to debond between the copper (II) sulfate and copper (II) chloride. The chloride in acid was, however, the only one of the two to produce a conventional etch pattern on the surface of the enamel.Significance. It is possible to render the enamel surface both retentive and active towards anaerobic adhesives, such that relatively unreactive substrates can be bonded to enamel using such adhesives. [Copyright &y& Elsevier]