Esters from castor oil functionalized with aromatic amines as a potential lubricant

Vegetable oils are very promising alternatives to fossil lubricants due to their abundance, low cost, excellent performance, and environmental friendliness. Due to its multifunctional structure, castor oil is an excellent precursor in the synthesis of new biolubricants. However, it showed poor thermal-oxidative stability and a higher pour point. This study used castor oil fatty acids prepared by transesterification (EHRO), epoxidation (TEPO), and oxirane ring opening with the aromatic amines aniline (ANIL) and p-anisidine (ANIS). The chemical structure of these oils was verified by ¹H and ¹³C NMR analysis, and mass spectrometry. Measurements show that the presence of an aromatic amine increases the viscosity resulting in 172 (ANIL) and 199 (ANIS) cSt at 40°C, but reduces viscosity index to 16 and 1, respectively. In addition, the amine groups can scavenge radicals increasing their thermal and oxidative stability. These products do not oxidize copper, and tribological analysis reveals that ANIS has the lowest torque with wear equivalent to commercial mineral lubricant NH-140.     

Niobium and tantalum recovery from the primary source and from tin slag,an industrial challenge: A review

Niobium (Nb) and Tantalum (Ta) are used to increase materials' mechanical resistance and produce lighter alloys. Worldwide Nb production reached 78 000 t in 2020. The reduced ore offer justifies the recycling of these metals from tin slag, contributing to the circular economy. Nb₂O₅ and Ta₂O₅ extraction either from the primary source or the tin slag is an industrial challenge. Nb and Ta dissolution processes already implemented are fluoride leaching, sulphuric leaching, alkaline leaching, and alkaline roasting. The fluoride process raises environmental concerns about waste control. The sulphuric method can be managed to have higher Nb and Ta extraction in a less aggressive process, if some changes are implemented, such as increasing the number of extraction steps, decreasing the pulp density, or increasing the temperature; however, the efficiency of this methodology must be tested for tin slag. The alkaline method seems to be more selective to Nb and Ta by reactants and temperature control. Despite those well-established Nb and Ta treatments, they must be adapted to recover Nb and Ta from slag. The slag has low Nb and Ta content, while high Si and Ca concentrations exist in the matrix. This paper brings the main methods used to extract the Nb and Ta from the primary resources and an overview of Nb and Ta recovery from the slag. This investigation comes as a tool to guide the development of new methods to recover Nb and Ta from low-grade sources such as tin slag.     

Highly Aligned Centrifugal Spun Polyacrylonitrile Nanofibers Collected and Processed with Automated Tracks

A parallel automated track collector is integrated with a rationally designed centrifugal spinning head to collect aligned polyacrylonitrile (PAN) nanofibers. Centrifugal spinning is an extremely promising nanofiber fabrication technology due to high production rates. However, continuous oriented fiber collection and processing presents challenges. Engineering solutions to these two challenges are explored in this study. A 3D-printed head design, optimized through a computational fluid dynamics simulation approach, is utilized to limit unwanted air currents that disturb deposited nanofibers. An automated track collecting device has pulled deposited nanofibers away from the collecting area. This results in a continuous supply of individual aligned nanofibers as opposed to the densely packed nanofiber mesh ring that is deposited on conventional static post collectors. The automated track collector allows for simple integration of the postdraw processing step that is critical to polymer fiber manufacturing for enhancing macromolecular orientation and mechanical properties. Postdrawing has enhanced the mechanical properties of centrifugal spun PAN nanofibers, which have different crystalline properties compared with conventional PAN microfiber. These technological developments address key limitations of centrifugal spinning that can facilitate high production rate commercial fabrication of highly aligned, high-performance polymer nanofibers.     

Expanding the Genetic Code in Xenopus laevis Oocytes

Heterologous expression of ligand‐gated ion channels (LGICs) in Xenopus laevis oocytes combined with site‐directed mutagenesis has been demonstrated to be a powerful approach to study structure–function relationships. In particular, introducing unnatural amino acids (UAAs) has enabled modifications that are not found in natural proteins. However, the current strategy relies on the technically demanding in vitro synthesis of aminoacylated suppressor tRNA. We report here a general method that circumvents this limitation by utilizing orthogonal aminoacyl‐tRNA synthetase (aaRS)/suppressor tRNA_CUA pairs to genetically encode UAAs in Xenopus oocytes. We show that UAAs inserted in the N‐terminal domain of N‐methyl‐D ‐aspartate receptors (NMDARs) serve as photo‐crosslinkers that lock the receptor in a discrete conformational state in response to UV photo treatment. Our method should be generally applicable to studies of other LGICs in Xenopus oocytes.     

Influence of particle size and fluid fraction on rheological and extrusion properties of crosslinked hyaluronic acid hydrogel dispersions

Crosslinked hyaluronic acid (HA) hydrogels are widely used in gel/HA fluid formulations as a viscosupplement to treat joint diseases; thus, it is important to characterize these hydrogels in terms of their particle size and to investigate the effects of the gel/fluid mixtures on their rheological properties and extrusion force. Hydrogels previously crosslinked with divinyl sulfone were sheared in an Ultra‐Turrax unit to produce particles with mean diameters ranging from 20 to 200 μm. Hydrogels with 75–100 μm mean diameters were also evaluated in dispersions containing a 20–40% mass fraction of HA fluid. The mean diameters were measured by laser light scattering and the rheological behavior was determined by oscillatory and steady measurements in parallel plate geometry. The HA hydrogels exhibited the typical behavior of so‐called weak gels, as analyzed by the storage and loss moduli G′ and G″, respectively. The viscoelasticity, the viscosity, and the extrusion force increased with the hydrogel particle size. The fluid phase dispersions decreased both moduli. At 40% fluid fraction, the gel characteristics were lost and the dispersion behaved as a fluid. Based on these results, the particle size and HA fluid fraction in hydrogel dispersions may be optimized to develop more efficient viscosupplement formulations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Linear viscoelastic behavior of compatibilized PMMA/PP blends

In this work, the morphology and linear viscoelastic behavior of PMMA/PP blends to which a graft copolymer PP‐g‐PMMA has been added was studied. The copolymer concentration varied from 1 to 10 wt % relative to the dispersed phase concentration. The rheological data were used to infer the interfacial tension between the blended components. It was observed that PP‐g‐PMMA was effective as a compatibilizer for PMMA/PP blends. For PP‐g‐PMMA concentration added below the critical concentration of interface saturation, two rheological behaviors were observed depending on the blend concentration: for 70/30 blend, the storage modulus, at low frequencies, increased as compared to the one of the unmodified blend; for 90/10 blend, it decreased. For 90/10 blend, the relaxation spectrum presented an interfacial relaxation time related to the presence of the compatibilizer (τ_β). For PP‐g‐PMMA concentrations added above the critical concentration of interface saturation, the storage modulus of all blends increased as compared with the one of the unmodified blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modification of Polycarbonate and Glycol Modified Poly(ethylene terephthalate) by Addition of Silica‐Nanoparticles Grafted with SAN Copolymer Using “Classical” and ARGET ATRP

This study presents a nanocomposite manufacturing route starting from non‐functionalized nanosilica and SAN surface modification via “grafting from” ATRP up to processing of transparent polycarbonate and glycol modified poly(ethylene terephthalate) nanocomposites. Synthesis limitations of low molecular weight graft SAN derived from “classical” ATRP are overcome by employment of the emerging ARGET ATRP. Mechanical investigations of polycarbonate and glycol modified poly(ethylene terephthalate) nanocomposites present up to 80% enhancement of creep performance and additionally 70% enhancement against wear abrasion for glycol modified poly(ethylene terephthalate) nanocomposites. Strength and tensile modulus are only moderately influenced by the addition of nanoparticles. Morphological studies confirm that the present modification route is able to create uniform dispersions of single particles and small particle aggregates in polymer matrices.

     

Modeling of the Extraction Equilibrium of Copper from Sulfate Solutions with Acorga M5640

The extraction equilibrium of copper from sulfate media with the aldoxime Acorga M5640 in ShellSol D70 has been investigated. The distribution results were interpreted by taking into account the nonideality of the aqueous phase. The activity of copper and hydrogen ions in the target systems CuSO₄/H₂SO₄/Na₂SO₄ and CuSO₄/H₂SO₄/Fe₂(SO₄)₃/ZnSO₄ were calculated through the speciation of the aqueous solutions and by applying the Pitzer model. The experimental pH values were found in good agreement with the predicted pH values. A model considering the dimerization of the aldoxime extractant was proposed to predict the distribution ratio and the copper loading isotherms. The extraction constant at infinite dilution and the apparent dimerization constant were evaluated from the experimental data and were found to be 10^{3.06 ± 0.07} and 51 ± 9 M^?1, respectively, at 25°C.     

Adaptive Finite Element Analysis of Air Flow Inside Grain Dryers

ABSTRACT

This paper presents a simulation study of air flow inside dryers. An adaptive finite element methodology for two-dimensional problems was developed. This study is the first application of nadaptive techniques to such tupe of problems. The formultion is generic and can be easily extended to three-dimensional analysis. Several dryer configurations were studied in order to verify the efficiency and accuracy of the proposed methodology. Results agreed well with experimental data and show significant imporvements when compared to the conventional finite elements analysis.     

MASS TRANSFER AND DIFFUSION COEFFICIENT DETERMINATION IN THE WET AND DRY SALTING OF MEAT

ABSTRACT

Dehydrated salted meat is widely used in Brazil as a very important source of animal protein. The main objective of this kind of processing is water removal. initially by osmotic pressure changes and then by drying, resulting in a product with intermediate moisture levels.

In this work, mass transfer and salt diffusion in pieces of meat submitted to wet and dry salting were studied. Slabs of beef m. trapezius with an infinite plate geometry were salted in a NaCl saturated solution or in a dry salt bed, at two temperatures (10 and 20°C) and different time exposures (120 min and 96 hours). Equilibration studies were extended up to six days.

It was observed that water loss increased with salt uptake, for increasing periods of times. At 20°C the moisture loss was higher than it was at 10°C in both salting processes. On the other hand, the kinetics of salt uptake and moisture loss were of greater importance in the process of dry salting than in that of wet salting.

The salt diffusion coefficient for wet salting was 0.26 × 10^?10m²/s at20°C and 0.25 × 10^?10 m²/s at 10°C and for the dry salting the values were 19.37 × 10^?10 m²/s at 20°C and 17.21 × 10^?10 m²/s at 10°C.