Journal of Thermal Analysis and Calorimetry最新文献

This study aimed to study the interaction between two different açaí extracts used in synthesis of hybrid polymeric films based on chitosan–clay and evaluate its morphological and physical–chemical properties, indeed antibacterial and antioxidant activities. Films with acidified açai extract (FEAA) and non-acidified açai extract (FEBANA) were prepared using the casting method. It was possible to observe a surface with a rough appearance, varying according to the added extract concentration using SEM photomicrographs. The reflection peaks were similar to the Chit–Clay film (2θ = 14° and 16.8°) and the reduction in the degree of chitosan crystallinity for the FEBANA films in relation to FEAA films. The TG data also show that the FEBANA films have a higher percentage of water of hydration than the FEAA films, corroborating this state of anhydrous films for FEAA and state of hydrated films for FEBANA. The FEBANA films were two stretches in the region between 842 and 962 cm⁻¹, and a shoulder 1095 cm⁻¹ covered by bands 1025 cm⁻¹ (Si–O–Si) and can attributed to the PEG plasticizer. This greater detection of PEG stretches in the FEBANA films suggests a greater concentration of PEG on the surface of the FEBANA film. MIC microbiology demonstrated that both types of extracts were capable of inhibiting Gram (−) strains, Escherichia coli and Pseudomonas aeruginosa, and Gram ( +) strains, Staphylococcus aureus and Staphylococcus epidermidis. In disk diffusion, the acidified extract showed inhibition activity for Edwardsiella tarda, Enterococcus faecium and Streptococcus pyogenes. Both extracts are effective in inhibiting the growth of both Gram (−) and Gram ( +) bacteria. The FEAA polymeric films showed a higher degree of recovery, reversible chemical bonding with the matrices and consequently greater DPPH free radical scavenging capacity compared to the FEBANA polymeric films. The FEAA and FEBANA films present characteristics of releasing active ingredients from the hybrid polymeric film and can be applied in edible packaging or use in biodegradable smart packaging or as food biopreservative; or even, in pharmaceutical release systems for releasing active ingredients onto the skin, as organic active ingredient release membranes for skin health and beauty, wound healing or even as adjuvants in tissue bioengineering for skin reconstruction after burns and in plastic skin surgery as biodegradable films.

The growing need for renewable and sustainable energy sources has prompted researchers to explore alternative fuels for engines traditionally powered by gasoline or diesel. Biodiesel derived from tamarind oil shows great potential as a sustainable fuel due to its renewable and eco-friendly nature. This investigation emphasizes the efficiency, emissions, and combustion characteristics of tamarind seed-based biodiesel blends with magnetite (Fe₃O₄) nanoparticles in a direct ignition engine. The magnetite nanoparticles in concentrations of 50 and 100 ppm are added to tamarind biodiesel blends with the help of an ultrasonicator. The prepared fuels were tested in a single-cylinder, four-stroke, vertical compression ignition engine. The experimental results revealed that the TME20M100 blend exhibits an increase in brake thermal efficiency by 5.85%, and SFC decreased by 6.18% with the maximum values of HRR and cylinder pressure are 44.5 J/°CA and 69.58 bar, respectively. Additionally, the TME20M100 blend exhibited a significant reduction of 27.32% in CO emissions, 7.93% in HC emissions, 4.05% in NOx emissions, and 3.23% in smoke emissions, as compared to the TME20. This study presents a promising approach to producing high-performance, eco-friendly biodiesel, contributing to the broader adoption of renewable energy sources.

The oxidation process of fuels during storage affects their quality and has been a recurring problem in the use of neat biodiesel or diesel/biodiesel blends. One of the most significant and undesirable change that occurs due to deterioration is the formation of sediments and gums (SG’s). SG’s are degradation products resulting from oxidation process of fuels and have a negative effect on the fuel atomization process, reducing its calorific value and ignition quality (cetane number). Diesel fuel sold in Brazil is a diesel/biodiesel blend containing 14% by volume of biodiesel (B14), which increases fuel degradation during storage time. The main aim of this study was to evaluate the effect of the biodiesel content in diesel/biodiesel fuel blends on the SG content formed after storage period using thermogravimetric analysis (TGA). Blends were prepared using methyl soybean biodiesel (B100) and S10 diesel with different volumetric biodiesel percentage, from 10% (B10) to 50% (B50). The samples were stored in amber glass bottles (similar to ASTM D4625), at room temperature and protected from light. Every 30 days, bottles of each mixture were opened and a sample collected for analysis. This procedure was repeated for six consecutive months. Blends oxidized and not oxidized (immediate age) were analyzed using thermogravimetry (TG) and derivative thermogravimetry (DTG). The physicochemical properties of blends were also evaluated, such oxidation stability, kinematic viscosity at 40 °C and specific mass a 20 °C. Size exclusion chromatography analyses (SEC) were also performed. Thermogravimetry shows that, as the B100 content increases regarding diesel, the interactions between the two fuels are distinct, which result in changes in the TG/DTG curve profile. It is also observed that the increase in B100 promotes the retardation of the mass loss steps of the blends to higher temperatures. The final (T_endset) and the maximum (T_onset) degradation temperatures are affected as well. The TG/DTG curves of the sample showed that increasing biodiesel content in the blend, the percentage of SG formed for the same aging age increases. Moreover, the formation of SG is correlated with the proportion of the blend constituents. The profiles of TG/DTG curves for each blend are a function of the added percentages of biodiesel in the mixture. The experimental results obtained showed that the degradation products formed during the storage of fuels, sediments/gums (SG’s), can be quantified using thermogravimetric techniques.

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Developing stable biopharmaceutical formulations is of paramount importance and is typically achieved by incorporating surfactants as stabilising agents, such as polysorbate 20 and 80. However, little is known about the effect surfactant grade has on formulation stability. This study evaluates the effect of regular grade and Super-refined™ polysorbates 20 and 80 and their interaction with model proteins, namely β-lactoglobulin (β-Ig), human serum albumin (HSA) and immunoglobulin gamma (IgG), using isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC). ITC results indicated that all four polysorbates underwent binding interactions with β-Ig and HSA, yet no interaction was observed with IgG this is postulated to be a consequence of differences in secondary structure composition. Surfactant binding to β-Ig occurred at ratios of ~ 3:2 regardless of the surfactant used with dissociation constants ranging from 284 to 388 µM, whereas HSA bound at ratios of ~ 3:1 and dissociation constants ranging from 429 to 653 µM. Changes in enthalpy were larger for the surfactant interactions with HSA compared with β-Ig implying the former produced a greater binding interaction than the latter. DSC facilitated measurement of the temperature of unfolding of each protein with the presence of each polysorbate where results further confirmed interactions had occurred for β-Ig and HSA with an increased unfolding temperature between 4 and 6 K implying improved protein stability, yet again, no interaction was observed with IgG. This study thermodynamically characterised the role of polysorbates in protein stabilisation for biopharmaceutical formulations.

The purpose of this proposed research is to examine the two-dimensional couple stress fluid flow over an extensible cylinder. The flow rate was determined by convective boundary layer constraints and the presence of a magnetic field. A nonlinear convective expression is used to study the heat transfer process in the vicinity of the cylindrical surface, which has widespread applications in engineering and industrial sectors. Incorporating a thermal radiation source into the heat transfer process increases the effect of dissipative heat. The behavior of the flow is determined by its mathematical structure, which is then translated into ordinary differential equations by making suitable assumptions about similarity variables and stream function. The findings indicate that as the dimensionless couple stress parameter increases, fluid movement intensifies. Conversely, an increase in the Hartmann number (M) leads to a decrease in velocity. Additionally, varying the curvature parameter results in higher values for both temperature and fluid velocity profiles. The coefficient of skin friction rises with the curvature parameter but decreases with the Grashof number. Furthermore, the heat transfer rate increases with higher curvature and decreases with the Grashof number, respectively. The present study includes a comparison with existing research to reinforce the proposed model.

Genipa americana L. is popularly known as jenipapo and has a potential herbal medicine with various pharmacological activities. Granules is a simple and useful pharmaceutical form to obtain herbal medicines in solid-state and has advantage due to protection of the bioactive compounds herbal extract. The aim of this study was to conduct studies of characterization of Genipa americana extract and its granules to evaluate their phytochemical, physicochemical and thermal properties. The crude extract of Genipa americana leaves was obtained by maceration using ethanol. A total of four Genipa americana granules were obtained using wet granulation process. Phytochemical characterization was performed: total phenol and total flavonoid contents and DPPH, FRAP and MDA assays. Physicochemical characterization was performed using SEM, FTIR, UV–Vis, dissolution profile and UFLC-DAD/UV analysis. Thermal characterization was performed using TG technique. The crude extract of Genipa americana and its granules showed the presence of iridoids (genipin and geniposides), flavonoids and phenolic compounds and genipin derivatives after hydrolysis experiment using the UFLC-DAD/UV. The DPPH assay showed antioxidant activity with an IC50 of 207.07 µg cm⁻³ for the Genipa americana extract and 198.34 to 298.71 µg cm⁻³ for the Genipa americana granules. The FRAP assay showed a good ability to reduce the iron III–TPTZ complex to iron II–TPTZ with values between 1092 and 1532 µM ferrous sulfate. g⁻¹ also explained by the presence of phenolic compounds and flavonoids. The maloaldehyde (MDA) assay showed acceptable levels and similar to the scientific literature. SEM analysis showed granules with morphology and particle size that characterize them as microparticles. FTIR analysis showed similarity between the identification bands of the crude Genipa americana granules with pharmaceutical excipients. The dissolution profiles of the Genipa americana granules showed characteristics of highly water-soluble pharmaceutical compositions with total release of the genipin marker between 30 and 60 min. The Genipa americana granules showed moisture content between 4.27 and 11.6% by the thermogravimetric analysis. The granules indicated greater protection and stability for the Genipa americana extract in these pharmaceutical formulations. The wet granulation process proved to be suitable and low-cost for Genipa americana extract. The moisture content of the granules can cause variability in genipin content to be stored in appropriate environment and packaging.

Over the years, several materials have been used for restoration purposes, with different types of dyes and colour hues. Recently, some researchers have proposed geopolymers (GPs) or amorphous aluminosilicate polymers for these purposes. In this work, an alcohol-based grape marc extract (GME, obtained via dark maceration assisted with ultrasound) was used as a natural dyeing agent for metakaolin-based GPs. The geopolymerisation occurrence was assessed by Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction analysis, while the colour of the resulting material was determined through the colorimetric analysis in the L*a*b* colour space. Additionally, the thermal stability of GME and GPs was investigated by thermogravimetry coupled with FT-IR spectroscopy. The microstructure, the reticulation stability, and the antimicrobial activity of GPs were examined through the scanning electron microscopy, the pH and ionic conductivity measurements, integrity, and mass loss tests. Overall, a coloured geopolymer with suitable thermal, antimicrobial, and mechanical properties was obtained, justifying its potential use in restoration or, more generally, in the construction field.

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To demonstrate the role of safety valves in enhancing the safety characteristics of lithium-ion cells, this study conducts a set of abusive testing including accelerating rate calorimetry testing, overheating testing, and overcharge testing. Additionally, the influence of safety valves on cells with different states of health (100%, 90%, and 80% SOH) and formats (14,650, 18,650, and 22,650) is investigated. The results reveal that safety valves have a substantial influence on the thermal runaway behaviour of cells. They effectively mitigate the risks and hazards associated with thermal runaway during overheating and ARC conditions. Beyond that, the presence of a safety valve can prevent thermal runaway triggered by overcharge. It is observed that cells with lower SOH and/or smaller diameters are more prone to experiencing earlier thermal runaway. Furthermore, this research finds that the influence of safety valves is more pronounced in cells with less degradation and/or smaller formats.