Aluminum Stearate Research Articles

Effect of Thickener Type on Change the Tribological and Rheological Characteristics of Vegetable Lubricants.

This paper presents the results of a study on the effect of the dispersed phase on the lubricating and rheological properties of selected lubricant compositions. A vegetable oil base (rapeseed oil) was used to prepare vegetable lubricants, which were then thickened with lithium stearate, calcium stearate, aluminum stearate, amorphous silica, and montmorillonite. Based on the results of the tribological tests of selected lubricating compositions, it was found that calcium stearate and montmorillonite have the most beneficial effect on the anti-wear properties of the tested lubricating greases, while silica thickeners (amorphous silica and montmorillonite) provide the effective anti-wear protection in compared to the lubricants produced on lithium and aluminum stearate. The lowest structural viscosity was found for grease thickened with montmorillonite. Much higher values of this parameter were observed for composition, where aluminum stearate was the dispersed phase, while the highest value of structural viscosity was observed for composition, where aerosol-amorphous silica was the thickener. The composition thickened with amorphous silica had the highest yield point value, while the composition in which montmorillonite was the dispersed phase had the lowest value. Dynamic viscosity decreases with temperature, which is characteristic of lubricants. No significant differences in dynamic viscosity were found for the lubricating compositions tested at temperatures above 50 [°C]. The most favorable rheological properties were observed for composition, which was produced using calcium stearate, as it allows the lowest dynamic viscosity at -20 [°C]. Lubricants produced with lithium stearate or aluminum stearate were characterized by higher viscosity at low temperatures. For grease, in which the lithium stearate was used as a thickener, the value of the elasticity index determines the weak viscoelastic properties of tested grease and a greater tendency to change structure under the influence of applied forces. For vegetable grease thickened with aluminum stearate, more than 15 times lower values of the MSD function were observed, and the calculated elasticity index value proves the stronger viscoelastic properties of the aluminum stearate grease in relation to grease thickened with the lithium stearate. The elasticity index value for grease thickened with amorphous silica was lower than for greases thickened with lithium and aluminum stearate, indicating its stronger viscoelastic properties in relation to these two greases. For grease composition prepared on the vegetable oil base and thickened with montmorillonite. The value of the elasticity index was lower than most of the tested grease compositions, without the composition, in which the calcium stearate was used as a thickener. Such results testify to moderately strong viscoelastic properties, which leads to the conclusion that the produced lubricant was a stable substance on changes in chemical structure under the influence of variable conditions prevailing during work in tribological joints.

Influence of type of aluminium stearate on triboelectrification of dry-coated surfaces of functionalised glass beads

Triboelectrification of powders and grains is deleterious in a large number of manufacturing operations, due to its adverse effect on process consistency and reliability. To mitigate it, charge neutralisers are commonly employed. However, their selection is often based on trial and error. This study is conducted to systematically examine the influence of the ionic polarity strength of a charge neutraliser, specifically aluminium stearate (AlSt), on charge transfer. AlSt has three types with different numbers of stearate chains, thereby influencing the electron exchange propensity of the molecule. The experiments involved surface-treated glass beads in the sieve size range of 90–150 µm (to make them hydrophilic by acid washing or hydrophobic by silanisation), then coated with the three forms of AlSt (mono-, di- and tri-) for charge mitigation. These coated beads were subjected to aerodynamic dispersion to cause triboelectrification, in order to quantitatively evaluate their charge neutralising effect. The experiments were conducted with four contact surfaces: stainless steel, copper, aluminium, and polytetrafluoroethylene (PTFE). Both acid-washed and silanised glass beads exhibited negative charging against aluminium, copper and stainless steel (typically around 22–44 nC/g), but positive charging against PTFE (around 90 nC/g and 19 nC/g for acid-washed and silanised, respectively), despite having significantly different surface functional groups. A complex trend is observed for the effect of the amount of AlSt present on the surfaces, the type of AlSt and the surface treatment. A relatively good charge reduction behaviour was seen for AlSt-coated acid washed glass beads, but for silanised glass beads, AlSt coating actually increases their charge level.

Effect of surface modification of metal powders (by aluminum stearate) on the properties of metal injection molding feedstock

Metal injection molding (MIM) is a net-forming technology for manufacturing miniature metal parts, which can improve the manufacturing accuracy of complex-shaped parts. In this study, aluminum stearate was used to modify the 17-4PH stainless steel powder, the binder was composed of (PMMA) and (PEG) with the volume ratio of 7:3. The effects of aluminum stearate surfactant amount on the feedstock viscosity, water debinding rate and thermal debinding shape were studied. The results showed that the coating of aluminum stearate breaks the agglomeration between the powders and decreases the viscosity of the feedstock. When the addition of aluminum stearate was 0.6wt% of the powder mass, the melt index, density and flexural modulus of the feedstock were 81.5 g/10 min, 5.44 g/cm3, and 1643Mpa, respectively, and the thermal debinding shape retention was the best of all debinded parts. However, too much aluminum stearate makes the feedstocks thicker and the green part weaker.

Study on Mechanical and Durability Properties of Aerated Concrete Block Containing Construction and Demolition Waste with Aluminium Stearate Powder Along with Alkaline Solution and Considering Accelerated Curing Tank

Study on Mechanical and Durability Properties of Aerated Concrete Block Containing Construction and Demolition Waste with Aluminium Stearate Powder Along with Alkaline Solution and Considering Accelerated Curing Tank

Sedimentation Stability of Magnetorheological Fluids: The State of the Art and Challenging Issues.

Among the many factors causing particle sedimentation, three principal ingredients are heavily involved: magnetic particles, a carrier liquid (base oil), and additives (surfactant). Therefore, many works have been carried out to improve the sedimentation stability of magnetorheological fluids (MRFs) by adopting the three methods. In the particle modification stage, the weight concentration, size distribution, particle shape, coated materials, and combinations of different sizes of the particles have been proposed, while for the modification of the carrier liquid, several works on the density increment, wettability control, and the use of natural oils, lubricant oil, grease, and ethyl- and butyl-acetate oils have been undertaken. Recently, in certain recipes to improve sedimentation stability, some additives such as aluminum stearate were used to increase the redispersibility of the aggregated particles. In addition, several works using more than two recipes modifying both the particles and base oils are being actively carried out to achieve higher sedimentation stability. This review article comprehensively introduces and discuses the recipes to improve sedimentation stability from the aspects of the three ingredients. A few conceptual methodologies to prevent the sedimentation occurring via a bottle's storage on the shelves of the application systems are also presented, since, to the author's knowledge, there has not been a report on this issue. These are challenging works to be explored and developed for successful application systems' MRFs.

Alginate-oil gelator composite foam for effective oil spill treatment

Oil spills threaten ecosystem and health seriously. Porous foams have been proved as ideal candidates for oil absorbents, however, many with poor oil retention (re-bleeding). Here, we creatively developed a composite foam oil absorbent capable of oil absorption and oil gelation, based on porous alginate foam and hydroxyl aluminum stearate oil gelator. The microstructure of alginate foam can be adjusted by the addition of t-butanol in the solvent, and long alkyl chains of gelator endow foam skeleton with good hydrophobicity, avoiding secondary pollution from traditional hydrophobic chemical modification. Interconnected skeleton decorated by oleophilic gelators contributes to high oil absorption. Oleophilic gelator can self-assemble into 3D network to entrap oils to form gels, giving rise to effective oil retention, realizing the integration of high oil absorption and oil retention. The natural abundant, low-cost composite foam would be promising for tackling oil spills.

Regularities of the Formation of a Green Superhydrophobic Protective Coating on an Aluminum Alloy after Surface Modification with Stearic Acid Solutions

It has been shown that solutions of stearic acid in a dimethyl sulfoxide–water binary mixture allow superhydrophobic protective coatings to be created on an aluminum alloy surface with a minimum impact on the environment. The superhydrophobicity and self-cleaning ability of the coating that we developed have been confirmed by measurements of droplet wetting angles and roll-off angles. These properties appear due to the formation of a multimodal micro-rough surface that mainly consists of aluminum stearate. The coatings formed in this manner have been studied by ellipsometry, XPS, and scanning probe microscopy. Their protective ability has been estimated by the “droplet-express” method and in a salt fog chamber. The protective ability of the coating is determined by the DMSO/H2O ratio, the concentration of stearic acid, and the duration and temperature of modification of the aluminum alloy; it is controlled by a competition between the processes of aluminum stearate formation and hydrolysis. It has been shown that adsorption of stearic acid on an aluminum stearate coating increases its permeability and decreases its protective capability. The results presented in this article are useful for optimizing the conditions of applying green superhydrophobic stearate coatings on aluminum alloys in order to achieve a maximum protective effect.

Aspects Concerning the Fabrication of Magnetorheological Fluids Containing High Magnetization FeCo Nanoparticles

Recently, our collaborative work in the fabrication of a magnetorheological fluid (MRF) containing high magnetization FeCo nanoparticles (NPs, fabricated in our laboratories using the chemical reduction technique; MS = 212 Am2/kg) as magnetic fillers have resulted in a new MRF with superior performance up to 616.7 kA/m. The MRF had a yield stress value of 2729 Pa and good reversibility after a demagnetization process. This value competes with the best ones reported in the most recent literature. Nevertheless, the fabrication process of this type of fluid is not an easy task since there is a strong trend to the aggregation of the FeCo NPs due to the strong magnetic dipolar interaction among them. Thus, now we present the analysis of some aspects concerning the fabrication process of our FeCo NPs containing MRF, mainly the type of surfactant used to cover those NPs (oleic acid or aluminium stearate) and its concentration, and the procedure followed (mechanical and/or ultrasound stirring) to achieve a good dispersion of those magnetic fillers within the fluid.

Highly stable CsPbBr3 perovskite quantum dots incorporated in aluminum stearate

CsPbBr3 perovskite quantum dots (PQDs) have drawn much attention for their high photoluminescence quantum yield and great potential in optoelectronic applications. However, they suffer from poor stability under humid condition. This paper reports CsPbBr3 PQDs incorporated in aluminum stearate (AlSt3) matrix via an improved co-precipitation approach, in which AlSt3 not only acted as hydrophobic matrix to protect CsPbBr3 PQDs from surrounding environment, but also passivated the surface of PQDs via the coordination bond of St-Cs and St-Pb, as well as bond between Al3+ and Br−. By this method, the as-synthesized CsPbBr3-AlSt3 composites exhibited excellent stability in ambient condition even directly in water for more than 60 days. With the CsPbBr3-AlSt3 composites (green emission) used as color-conversion layer, a white light-emitting diode (WLED) was fabricated with a high color rendering index (Ra) of 90 and a low color temperature (Tc) of 4929 K. These results suggest that this method pave an effective way to stabilize CsPbBr3 PQDs, which is of great importance for their further application.

The influence of type of dispersed phase on rolling contact fatigue of lubricating greases on mineral base oil

The paper discusses the influence of type dispersed phase on value of rolling contact fatigue of bearings lubricated with selected lubricating compositions. The compositions, which were produced on the mineral base oil were thickened of lithium stearate, calcium stearate, aluminum stearate, lithium complex soap and modified silica, montmorillonite, and polytetrafluoroethylene were evaluated.
 Were carried out the investigations of rolling contact fatigue (pitting) of bearings, which were lubricated of the compositions prepared on the above-mentioned thickeners. Then was evaluated the influence of various thickeners on changes of rolling contact fatigue. The tribological tests were carried out using T-03 four-ball machine under high load conditions.
 On the basis of obtained results it may be concluded, that used of thickeners such as: modified amorphous silica, montmorillonite and polytetrafluoroethylene to produce of lubricating compositions, positively affected on the change of rolling contact fatigue of tribosystems lubricated with the above-mentioned compositions in comparison to the compositions, when as a dispersed phase were used a soap thickeners.

Effects of solid lubricants on properties of Al-Si-SiC composite powder produced by gas atomization technique

Al-Si-SiC composites powder was analyzed in this research. The powder was made by gas atomizing process. Powder characterization was done to observe its morphology, particle size distribution and thermal properties. Effects of lubricants were intensively investigated in this research with compositions and pressure variables. It is assumed that higher amount of solid lubricant put into the powder, the lower ejection force needed to take out compacted powder. Finding appropriate solid lubricant is necessary to improve green and sintering properties. EBS (ethylene bis stearamide), aluminum stearate, zinc stearate and paraffin wax were used for investigation. Sintering under ultra high purity nitrogen gas 99.9999% was carried out to produce high density material. SEM-EDS and XRD were carried to characterize this powder. SiC particles in this powder prohibit to achieve optimum sintering properties of Al-Si-SiC due to their resistance during compaction which leads to form pores and lower sintering density. And ethylene bis stearamide (EBS) seems to be suitable solid lubricant for this powder by giving lower ejection force, flowability and higher sintering density for 93.5%.

Rita Letendre’s Oil Paintings from the 1960s: The Effect of Artist’s Materials on Degradation Phenomena

ABSTRACT This paper describes an investigation into the causes of specific degradation phenomena in three oil paintings from the 1960s by eminent Indigenous Canadian painter Rita Letendre. A comprehensive technical study of the paintings was undertaken using a combination of SEM-EDS, FTIR spectroscopy, Py-GC-MS, Raman spectroscopy, XRD, and polarised light microscopy to determine pigments, fillers, additives, paint medium, and degradation products. Compositional factors, including high abundances of manufacturers’ additives such as aluminum stearate and castor wax, have likely contributed to the formation of oil exudates and fatty acid efflorescence. Cross sections illustrated an inhomogeneous distribution of additives and incomplete mixing of components in some colours. This appears to be due to the migration of components over time and also to Letendre’s technique, which included application of thick paint directly from the tube and the addition of extra medium to some impastos. Cracking, lifting, and protrusions in several areas were caused by the crystallization of zinc soaps below the paint surface. FTIR mapping allowed the spatial distribution of crystalline and ionomeric-type zinc soaps to be determined within a problematic paint layer.

Preparation and characterization of metformin hydrochloride controlled-release tablet using fatty acid coated granules

Metformin hydrochloride (MFM) is often used as a controlled-release (CR) tablet to reduce dosing frequency. However, the MFM CR tablet contains significant amounts of excipients and the tablet size is also large. Dosing convenience and patient compliance can be increased by reducing the size of the CR tablets. The aim of this study was to prepare and evaluate the MFM controlled-release tablet (MFM-CRT) using two types of release modulators, inner and outer. The MFM-CRT was prepared by coating the MFM granules using a binder solution containing aluminum stearate (ALS) as the inner release-modulator, and polyethylene oxide (PEO) as the outer release-modulator. The dispersion stability of the binder solution was optimized by the dispersion analyzer. The MFM-CRT was evaluated for dissolution rate and tablet volume. Additionally, dissolution behavior and dissolution kinetics of the MFM-CRT were analyzed using micro-computed tomography (micro-CT). Although the optimal MFM-CRT showed no difference in the release rate as compared to the commercially available product of Glucophage® XR 500 mg (f2 value: 72), the length of the long axis was reduced by 6 mm and the weight was reduced by about 27%. We expect patient compliance to improve because of effective sustained release and volume reduction of MFM-CRT.

Investigation of pro-oxidant agents’ effects on the ageing of polypropylene bags

ABSTRACTIn this work, the effects of calcium, aluminium and zinc stearates as pro-oxidant agents on the degradation of polypropylene (PP) bags were studied under natural weathering of Mediterranean climate. Samples were taken off periodically and characterised. Tensile properties, structural modifications, morphological and thermal properties were investigated. All the considered properties were affected by the presence of the three pro-oxidant agents. The pro-oxidants can be classified as follows: Zinc stearate > Calcium stearate>Aluminium stearate.

Facile fabrication of superhydrophobic aluminum surfaces by chemical etching and its anti-icing/self-cleaning performances

In order to ensure the safety of civil aviation during the freezing weather, the application of superhydrophobic coatings (surfaces) on the aircraft is a useful and supplemental way to mitigate the accumulation of frost, ice or snow. In this work, superhydrophobic surface with hierarchical structure on SAE AMS 4037 aluminum alloy plate is prepared through chemical etching using hydrochloric acid and hydrogen peroxide with lower concentration successfully. Comparing with the bare aluminum substrate (untreated-Al), the superhydrophobic surface (treated-Al-11) possessed an excellent resistance to water, which water contact angle (CA) is as high as 163.6°, combined with minimum roll-off angle (RA) and contact angle hysteresis (CAH). The influences on wettability caused by different molar ratios of hydrochloric acid and hydrogen peroxide are studied by CA, RA, CAH and root mean square roughness (Rq). Hierarchical structure with irregular honeycomb-like protrusions and depressions of treated-Al-11 is found through SEM. Furthermore, treated-Al-11 is characterized by FTIR, EDS and XPS, which are demonstrated the presence of the aluminum stearate (AlSA) molecules on surface of treated-Al-11. Anti-icing tests are revealed that the weight of ice on the surface of treated-Al-11 with superhydrophobicity is significantly less than that of other Al plates at the same test time. The ice weight on treated-Al-11 is 1.7751 g compared to 1.9952 g on untreated-Al surface when test time is 120 min Based on the results of self-cleaning tests, the surface of treated-Al-11 is clean, however solution residues are remained on the untreated-Al surface.

Facile electrodeposition of superhydrophobic aluminum stearate thin films on copper substrates for active corrosion protection

A facile aluminum based superhydrophobic thin films were electrodeposited by mixing aluminum isopropoxide (AlOx) with stearic acid (SA) onto the copper substrates via one-step method. The energy dispersive X-ray spectroscopy (EDS) attenuated total-reflectance Fourier Transmission infrared spectroscopy (ATR-FTIR) were used to confirm the presence of Al, C, and O as well as COOAl and CH bonds in the thin film. The water-roll off properties were analyzed by measuring the contact angle to study the superhydrophobic nature of fabricated films. Results show that superhydrophobicity with the water contact angle of 161 ± 1° and the contact angle hysteresis of 2 ± 1° were obtained with respect to the AlOx/SA molar ratio of 0.33. The morphology of the fabricated thin films consisted of uniform porous structures with surface roughness (rms) of 3 μm on the copper substrate. The addition of stearic acid plays an important role for the superhydrophobic property. Furthermore, the thin films and their anticorrosion behavior were investigated using 3.5 wt% corrosive aqueous NaCl electrolyte solution. The polarization resistance of the thin film is found to be 962 kΩ·cm2 as characterized by Tafel. Similarly, impedance value of 10 MΩ·cm2 was obtained from Electrochemical Impedance Spectroscopy (EIS). A simple fabrication of water-repellent superhydrophobic aluminum-based coating endues extremely high active in corrosion protection.

Influence of particle size in fluorine free corrosion resistance superhydrophobic coating - Optimization and stabilization of interface by multiscale roughness

Fluorine free superhydrophobic coatings with stabilized air-water interface had been fabricated by utilising different particle sized silica. Coatings were formulated with various composition of different sized nanosilica's along with nanotitania and aluminium stearate embedded in a matrix of silicone resin of Mn ∼1,65,000. The as-prepared coating exhibited higher contact angle (CA) 152.5° along with high mechanical properties like abrasion, adhesion and impact resistance. As particles with different sizes were incorporated in the coating, the interface was stabilized during immersion in water uptake study. In addition most of these coatings also exhibited exceptional corrosion resistance withstanding upto 1000 h of salt spray.

Investigating the effect of artists\u2019 paint formulation on degradation rates of TiO2-based oil paints

This study reports on the effect of artists’ paint formulation on degradation rates of TiO2-based oil paints. Titanium white oil paint exists in a multitude of different recipes, and the effect of the formulation on photocatalytic binder degradation kinetics is unknown. These formulations contain, among others, one or both titanium dioxide polymorphs, zinc oxide, the extenders barium sulfate or calcium carbonate and various additives. Most research performed on the photocatalytic degradation process focusses on pure titanium white-binder mixtures and thus does not take into account the complete paint system. Since photocatalytic oil degradation is a process initiated by the absorption of UV light, any ingredient or combination of ingredients influencing the light scattering and absorption properties of the paint films may affect the degradation rate. In this study three sets of experiments are conducted, designed using the design of experiments (DoE) approach, to screen for the most important formulation factors influencing the degradation rate. The benefits of using DoE, compared to a more traditional ‘one factor at a time approach’ are robustness, sample efficiency, the ability of evaluate mixtures of multiple components as well as the ability to evaluate factor interactions. The three sets of experiments investigate (1) the influence of the TiO2 type, (2) the impact of different mixtures of two types of TiO2, ZnO and the additive aluminum stearate and (3) the influence of common extenders in combination with photocatalytic TiO2, on the photocatalytic degradation of the oil binder. The impact of the formulation on the degradation rate became apparent, indicating the shortcoming of oversimplified studies. The protective effect of photostable TiO2 pigments, even in a mixture with photocatalytic TiO2 pigments, as well as the negative effect of extenders was demonstrated. Furthermore, the ambiguous role of ZnO (photocatalytic or not) and aluminum stearate is highlighted. Neither can be ignored in a study of degradation behavior of modern oil paints and require further investigation.

Salvinia inspired fluroine free superhydrophobic coatings

In this work, Salvinia inspired fluorine free superhydrophobic coatings were prepared by incorporating as-prepared metal silicates in silicone resin along with nanosilica, nanotitania and aluminium stearate. Coatings with different composition were prepared and applied by air spray method over precleaned mild steel panel. The superhydrophobicity and stability of coatings were studied. The pristine resin with no pigments and additives showed hydrophobic behaviour with water contact angle (WCA) of 93.5° and tilting angle (TA) of 60°. The WCA increased to 156.8° and TA to 28° with incorporation of metal silicates. Other properties like abrasion, adhesion, water uptake and water vapour permeation were also evaluated.

Wettability and Corrosion Behavior of Chemically Modified Plasma Electrolytic Oxidation Nanocomposite Coating

The aim of this paper was to investigate the effect of potassium stearate on the wettability behavior, corrosion resistance, roughness and thickness of reinforced and unreinforced plasma electrolytic oxidation (PEO) coatings with Si3N4 nanopowders. Morphological characteristic, corrosion behavior and wetting properties of the coatings were evaluated using SEM, cyclic polarization and Wilhelmy plate method, respectively. In order to obtain a better evaluation of the contact angle, roughness of the coatings was studied by AFM. The results indicated that the nanocomposite hydrophobic coatings have the best corrosion resistance. Potassium stearate could repel water from the holes of coating by reacting with aluminum and producing aluminum stearate. The contact angle of nanocomposite and normal PEO coatings was increased up to 65° due to the addition of potassium stearate. This additive could also increase the hysteresis contact angle up to 51°.