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.     

Glass foam of high compressive strength produced from photovoltaic module waste glass,eggshell, and clay

A glass foam (GF) of high specific compressive strength (12.17±1.91 MPa g⁻¹ cm⁻³) and low thermal conductivity (.121±.001 Wm⁻¹ K⁻¹) was produced from waste glass of photovoltaic module, eggshells, and bentonite clay. The influences of the amount of clay and heat-treatment temperature on the GFs final properties were assessed. X-ray diffraction results and the data of microscopic analyses demonstrated that addition of clay affected the structure and porosity of the GFs, and consequently their mechanical properties. On the basis of the mechanical property (density), the GF that composed of 80% waste glass, 10% clay, and 10% eggshell at the sintering temperature of 900°C was the best. The GFs reported in this study could serve as promising insulators in situations where high load support is required.     

Evolution of Chemistry,Morphology and Rheology of Various Polymer Systems along a Twin‐Screw Extruder

Intermeshing twin‐screw extruders have been recently identified as useful in special application niches such as the extrusion of PVC dry blends (counter‐rotating machines) and compounding operations (co‐rotating machines). Thus, it is of interest to study the mechanical and/or chemical effects that occur along the screw axis of the extruders, since they will dictate the characteristics and performance of the final material. This work aims at illustrating the usefulness of a simple experimental tool recently developed for the study of the physical, chemical and morphological evolution along the extruder of polymer based systems, data being presented and discussed for a number of composites and blends.     

Influence of ethylene‐co‐vinyl acetate copolymers on the flow properties of wax synthetic systems

Wax crystallization can cause serious damage to petroleum flow because as the viscosity increases, there is organic deposition in the pipe lines, which causes oil production reduction. Ethylene–vinyl acetate copolymers (EVA) are used as an alternative to prevent such problems. The influence of EVA copolymers on the properties of wax synthetic systems, composed of a solvent mixture and paraffin and petroleum asphalt residue (PAR), was evaluated in this work. The performance of EVA as a wax inhibitor depends on the molecular weight and vinyl acetate content of the copolymer and on the presence of the asphalt fraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1337–1348, 2002     

Phospholipids inTrypanosoma cruzi: Phosphoinositide composition and turnover

The polyphosphoinositides fromTrypanosoma cruzi were isolated by preparative thin-layer chromatography (TLC) and identified. When myo-[³H]inositol was present in the culture medium for five days, analyses showed the presence of phosphatidylinositol (PI), lysophosphatidylinositol (lysoPI), phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP₂). Short-term incubation with³²P_i led to higher percentages of incorporation into phosphatidylethanolamine (PE), lysophosphatidylethanolamine (lysoPE) and PI compared to the other glycerophospholipids. The phosphoinositides (PI, PIP and PIP₂) contained a larger proportion of unsaturated than saturated fatty acids. High proportions of 18∶2 were found in the three phosphoinositides analyzed, whereas the major saturated fatty acid was 18∶0. Watersoluble inositol phosphates (IP, IP₂ and IP₃) were also identified.     

Essentiality of dietary ω3 fatty acids for premature infants: Plasma and red blood cell fatty acid composition

Pre-term infants, that are not breast-fed, are deprived of vital intrauterine fat accretion during late pregnancy and must rely on formula to obtain fatty acids essential for normal development, particularly of the visual system. Preterm infants (30 wk postconception) receiving human milk were compared to infants given one of the following formulae: Formula A was a commercial preterm formula with predominantly 18∶2ω6 (24.2%) and low (0.5%) 18∶3ω3; Formula B was based on soy oil and contained similar 18∶2ω6 levels (20%) and high 18∶3ω3 (2.7%); Formula C was also a soy oil-based formula (20% 18∶2, 1.4% 18∶3) but was supplemented with marine oil to provide ω3 long-chain polyunsaturated fatty acids (LCP) at a level (docosahexaenoic acid, DHA, 0.35%) equivalent to human milk. At entry (10 days of age), the fatty acid composition of plasma and red blood cell (RBC) membrane lipids of the formula groups were identical. By 36 wk postconception, the DHA content in lipids of group A was significantly reduced compared to that in the human milk and marine oil formula groups. Omega-3 LCP results were further amplified by 57 wk with compensatory increases in 22∶5ω6 in both plasma and RBC lipids. Provision of 2.7% α-linolenic acid in formula group B was sufficient to maintain 22∶6ω3 levels equivalent to those in human milk-fed infants at 36 wk but not at 57 wk. Effects on the production of thiobarbituric acid reactive substances and fragility of RBC attributable to the marine oil supplementation were negligible. The results support the essentiality of ω3 fatty acids for preterm infants to obtain fatty acid profiles comparable to infants receiving human milk. Formula for preterm infants should be supplemented with ω3 fatty acids including LCP. Based on a paper presented at the Symposium on Milk Lipids held at the AOCS Annual Meeting, Baltimore, MD, April 1990.     

Synthesis and characterization of epoxidized styrene–butadiene rubber/silicon dioxide hybrid materials

Hybrid materials were synthesized from epoxidized (68, 43, or 14%) styrene–butadiene rubber (SBR) and the hydrolysis product of tetraethoxysilane (TEOS) in situ under ultrasonic irradiation. The products were characterized with thermal analysis (differential scanning calorimetry and thermogravimetric analysis), stress–strain tests, scanning electron microscopy (including energy‐dispersive spectrometry), and swelling in tetrahydrofuran and water. The most transparent were those prepared from SBR with the highest degree of epoxidation, whereas those obtained from less epoxidized SBR and with larger amounts of TEOS showed distinct phases that could be considered two hybrid phases (one rich in TEOS and another rich in SBR). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 798–803, 2004     

Continuous polymerization in tubular reactors with prepolymerization: Analysis using two‐dimensional phenomenological model and hybrid model with neural networks

Continuous polymerization processes have advantages when large amounts of product are required; moreover, higher quality can be obtained because of the elimination of variability between batches. Tubular reactors are economically attractive because of their simple geometry and high heat exchange area; however, they are not commonly used for commercial purposes, mainly because of the large radial profiles. This study elucidates the operation of this kind of reactors in three different ways: first a detailed two‐dimensional mathematical model was developed, in which a complete visualization of all axial and radial profiles is possible, allowing a safe analysis at different operating conditions. In a second step a system composed of a continuously stirred tank reactor in series with a tubular reactor was used. A reduction in radial profiles can be clearly observed when prepolymerization is taken into account, improving both the homogeneity and the end properties of the polymer. In a third approach neural networks (NNs) were used in parallel with a one‐dimensional model. The objective of this study was to illustrate how NNs can improve the prediction capability when it is not possible to build a reliable model because of uncertainties in parameters and incomplete knowledge of the system. The NNs generated good results, showing that the hybrid model was able to accurately simulate the reactor, even when uncertainty in kinetic and diffusional parameters was imposed to the model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 871–882, 2004     

Study of nanofiber scaffolds of PAA,PAA/CS,and PAA/ALG for its potential use in biotechnological applications

In recent times, electrospun nanofibers have been widely studied from several biotechnological approaches; in this work, poly(acrylic acid) (PAA) solutions mixed with chitosan and alginate were electrospun and characterized to determine the behavior of these fibers when used in combination with bacteria, different samples were incubated with the bacterial strains: Streptomyces spp., Micromonospora spp., and Escherichia coli and a OD600 test was performed. The formation of nanofibers via electrospinning and the physicochemical properties of the obtained fibers were evaluated. Results showed that the presence of chitosan enhanced the thermal stability of PAA, since PAA/alginate fibers lost 5% of their mass at 41°C, whereas PAA/chitosan lost this amount at around 125°C. The fibers demonstrated suitable characteristics to be used as a bacteria bioreactor.     

Study of hydrogen evolution reaction in acid medium on Pt microelectrodes

This work describes the utilization of a Pt UME in the study of the hydrogen evolution reaction in 0.5 M H₂SO₄. A non-linear fitting procedure was employed in order to analyze polarization curves obtained at several temperatures (25–75 °C). The results revealed that the traditionally accepted model described by a Volmer–Tafel route fails to fit the obtained experimental data. In this sense, a new model was proposed involving the Volmer–Heyrovsky mechanism, being the Heyrovsky reaction rate determining step. To achieve the best fit between experimental and calculated data, the kinetic equations had to be proposed with a small value of the transfer coefficient (β<0.2). This unusual value was associated with an activationless process, which can also justify the limiting kinetic current (not diffusional) observed. Trying to get further insight into this possibility, the polarization studies were also performed on a surface modified by underpotentially deposited copper. With a degree of coverage as high as 0.8, the only observed effect on the polarization curves was a shift towards minor current values. This shift can be completely justified by the blocking of surface area. A change in mechanism was not observed albeit the Cu UPD eliminated the pairs of neighbor active sites necessary to the Volmer–Tafel pathway.