Mathematical modeling of the properties of thermal insulation materials based on hollow ceramic microspheres and phenylon

In this work, the creation of heat-insulating materials that are still operable at temperatures up to + 400 °C and have increased physical and mechanical characteristics was studied. This aim was achieved by using a heat-resistant polymer binder phenylon (an aromatic polyamide) and hollow ceramic microspheres, that were used as a filler. Phenylon was produced by OJSC «Polimersintez» in Vladimir. Hollow ceramic microspheres are the floating fractions of flue emissions from solid-fuel thermal power plants. Thermal insulation materials were made by mixing hollow ceramic microspheres with a phenylon solution in dimethylacetamide to the state of «wet sand». Then, the obtained substance was molded the solvent residues were removed. Furthermore, the main properties of the obtained materials were also studied. It was established that the thermal insulation material is characterized by high strength characteristics, has significant resistance to impact loads and is operable at temperatures up to 400 °C The developed thermal insulation materials are intended to be used in the construction of objects operating under the conditions of cyclic exposure to high temperatures (for example, power plants) and in the construction of objects operating under the conditions of cyclic exposure to high temperatures (for example, power facilities).

Currently Applied Extraction Processes for Secondary Metabolites from Lippia turbinata and Turnera diffusa and Future Perspectives

The poleo (Lippia turbinata Griseb.) and damiana (Turnera diffusa Wild) are two of the most valued species in the Mexican semidesert due to their medicinal uses. The conventional essential oil extraction process is hydrodistillation, and for the extraction of antioxidants, the use of organic solvents. However, these techniques are time-consuming and degrade thermolabile molecules, and the efficiency of the process is dependent on the affinity of the solvent for bioactive compounds. Likewise, they generate solvent residues such as methanol, hexane, petroleum ether, toluene, chloroform, etc. Therefore, in recent years, ecofriendly alternatives such as ohmic heating, microwaves, ultrasound, and supercritical fluids have been studied. These methodologies allow reducing the environmental impact and processing times, in addition to increasing yields at a lower cost. Currently, there is no up-to-date information that provides a description of the ecofriendly trends for the recovery process of essential oils and antioxidants from Lippia turbinata and Turnera diffusa. This review includes relevant information on the most recent advancements in these processes, including conditions and methodological foundation.

A Review on – Estimation of Residual Solvents by Different Analytical Method

Residual solvents are the unwanted substances (solvents) used or created throughout the manufacture of a excipients, drug or pharmaceutical formulation and don't seem to be utterly removed by sensible ways within the final finished product. These solvents may be harmful in nature. Therefore, analysis of residual solvents becomes a necessary tool for the standard management of prescribed drugs. The appropriate limits for these substances are given in ICH. Solvents are widely used during the manufacturing, purification and processing of pharmaceutical substances. The residues of these solvents must be removed to the extent possible, as they do not have any therapeutic effect but can cause undesirable effects in the consumers. These solvent residues concentrationshould not exceed the limits prescribed in the ICH guidelines. This present review work is emphasized on various techniques (Loss on drying, Thermogravimetric analysis, Near- IR spectroscopy).

Supercritical CO2 Extraction of Organic Solvents from Flunisolide and Fluticasone Propionate

In this work, Class 2 and Class 3 solvents contained in two corticosteroids, flunisolide (Fluni) and fluticasone propionate (Fluti), were reduced to a few ppm by supercritical CO2 extraction. The process was carried out at pressures from 80 to 200 bar, temperatures of 40 °C and 80 °C, and at a fixed CO2 flow rate of 0.7 kg/h. The results demonstrated that CO2 density is the key parameter influencing the extraction kinetics and the solvent final residue. In particular, in the range investigated, optimal pressure and temperature conditions for the extraction of residual organic solvents were found working at 200 bar and 40 °C, which corresponds to a CO2 density of 0.840 g/cm3. Operating in this way, total organic solvent residues were reduced from 13,671 ppm and 326 ppm to 12 ppm and 10 ppm for Fluni and Fluti, respectively.

Influence of Carbon Nanotube-Pretreatment on the Properties of Polydimethylsiloxane/Carbon Nanotube-Nanocomposites

Incorporating nanofillers into elastomers leads to composites with an enormous potential regarding their properties. Unfortunately, nanofillers tend to form agglomerates inhibiting adequate filler dispersion. Therefore, different carbon nanotube (CNT) pretreatment methods were analyzed in this study to enhance the filler dispersion in polydimethylsiloxane (PDMS)/CNT-composites. By pre-dispersing CNTs in solvents an increase in electrical conductivity could be observed within the sequence of tetrahydrofuran (THF) > acetone > chloroform. Optimization of the pre-dispersion step results in an AC conductivity of 3.2 × 10−4 S/cm at 1 Hz and 0.5 wt.% of CNTs and the electrical percolation threshold is decreased to 0.1 wt.% of CNTs. Optimum parameters imply the use of an ultrasonic finger for 60 min in THF. However, solvent residues cause a softening effect deteriorating the mechanical performance of these composites. Concerning the pretreatment of CNTs by physical functionalization, the use of surfactants (sodium dodecylbenzenesulfonate (SDBS) and polyoxyethylene lauryl ether (“Brij35”)) leads to no improvement, neither in electrical conductivity nor in mechanical properties. Chemical functionalization enhances the compatibility of PDMS and CNT but damages the carbon nanotubes due to the oxidation process so that the improvement in conductivity and reinforcement is superimposed by the CNT damage even for mild oxidation conditions.

A New Approach for the Microencapsulation of Clitoria Ternatea Petal Extracts by a High-Pressure Processing Method

Toxic organic solvent residues and the active substances of thermal degradation (such as anthocyanin and polyphenols) are always a concern with the liposomes produced by traditional techniques. The present study focuses on a new approach for the microencapsulation of Clitoria ternatea petal (CTP) extracts, which contain anthocyanins, by high-pressure processing (HPP) at room temperature. Thus, a series of CTP liposomes were prepared and their physicochemical properties were analyzed by laser granulometry and by scanning electron microscopy (SEM). The results revealed that the average particle size of the liposomes after HPP treatment increased gradually from 300 MPa to 600 MPa, possibly due to the aggregation of liposomes and damage to the phospholipid bilayers. For the preparation of liposomes by the HPP method at 300 MPa, the mean particle size, polydispersity index (PDI), and encapsulation efficiency were 240.7 nm, 0.37, and 77.8%, respectively. The HPP method provided a number of advantages over conventional methods (magnet stirring and ultrasonication) as it could allow liposome preparation with higher encapsulation efficiency, smaller size, and narrower, more reproducible particle size distribution. Conclusively, microencapsulation in the liposomes was successfully achieved with the fast-adiabatic expansion of HPP.

Montagem, testes operacionais e validação de uma unidade laboratorial para extração de compostos de matrizes vegetais utilizando fluidos pressurizados ou supercríticos como solventes

Extractions of compounds still use traditional methods, leaving solvent residues in the extracts. An alternative is the use of high-pressure solvents such as supercritical CO2 and pressurized liquefied petroleum gas (LPG). Based on this context, the objective of this work was to assemble an equipment for high-pressure extractions using CO2 or pressurized LPG as solvent. The project and assembling were divided into 3 steps. In the first step, the equipment was designed. Also, aluminum bars, pipes, valves, pressure gauges, thermostatic baths, a pump for solvent pressurization, a digital temperature controller, a band heater and a reactor with filters were purchased. In the second step, some adaptations were done in the structure and its components for improving the operation. In the third step, the equipment was effectively assembled. Thereafter, operational validation tests were performed in order to verify the operation and the necessity of adjustments. In addition, a Standard Operating Procedure was created in order to standardize the next operations. The equipment is suitable for the extraction of bioactive compounds from different plant matrices, providing satisfactory extraction yields.

Dendrimer grafted nanoporous silica fibers for headspace solid phase microextraction coupled to gas chromatography determination of solvent residues in edible oil

A recently prepared nanoporous G(1)-dendrimer supported SBA-15 solid phase microextraction fiber was successfully applied to the HS-SPME of solvent residues such as hexane, benzene, and toluene in edible vegetable oils followed by GC-FID.