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Supercritical Antisolvent Processing of Nitrocellulose: Downscaling to Nanosize, Reducing Friction Sensitivity and Introducing Burning Rate Catalyst.

ABSTRACT: A supercritical antisolvent process has been applied to obtain the nitrocellulose nanoparticles with an average size of 190 nm from the nitrocellulose fibers of 20 μm in diameter. Compared to the micron-sized powder, nano-nitrocellulose is characterized with a slightly lower decomposition onset, however, the friction sensitivity has been improved substantially along with the burning rate increasing from 3.8 to 4.7 mm·s-1 at 2 MPa. Also, the proposed approach allows the production of stable nitrocellulose composites. Thus, the addition of 1 wt.% carbon nanotubes further improves the sensitivity of the nano-nitrocellulose up to the friction-insensitive level. Moreover, the simultaneous introduction of carbon nanotubes and nanosized iron oxide catalyzes the combustion process evidenced by a high-speed filming and resulting in the 20% burning rate increasing at 12 MPa. The presented approach to the processing of energetic nanomaterials based on the supercritical fluid technology opens the way to the production of nitrocellulose-based nanopowders with improved performance.

SUBMITTER: Dobrynin OS

PROVIDER: S-EPMC6835986 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Supercritical Antisolvent Fractionation of Antioxidant Compounds from Salvia officinalis.

Project description:The increasing interest towards greener antioxidants obtained via natural sources and more sustainable processes encourages the development of new theoretical and experimental methods in the field of those compounds. Two advanced separation methods using supercritical CO2 are applied to obtain valuable antioxidants from Salvia officinalis, and a first approximation to a QSAR model relating molecular structure with antioxidant activity is explored in order to be used, in the future, as a guide for the preselection of compounds of interest in these processes. Separation experiments through antisolvent fractionation with supercritical CO2 were designed using a Response Surface Methodology to study the effect of pressure and CO2 flow rate on both mass yields and capability to obtain fractions enriched in three antioxidant compounds: chlorogenic acid, caffeic acid and rosmarinic acid which were tracked using HPLC PDA. Rosmarinic acid was completely retained in the precipitation vessel while chlorogenic and caffeic acids, though distributed between the two separated fractions, had a major presence in the precipitation vessel too. The conditions predicted for an optimal overall yield and enrichment were 148 bar and 10 g/min. Although a training dataset including much more compounds than those now considered can be recommended, descriptors calculated from the σ-profiles provided by COSMO-RS model seem to be adequate for estimating the antioxidant activity of pure compounds through QSAR.

| S-EPMC8431610 | biostudies-literature

Formation of Fine Particles from Curcumin/PVP by the Supercritical Antisolvent Process with a Coaxial Nozzle.

Project description:The production of fine particles via the supercritical carbon dioxide (SC-CO2) antisolvent process was carried out. The experiments were conducted at temperatures of 40-60 °C and pressures of 8-12 MPa with a 15 mL min-1 carbon dioxide (CO2) and 0.5 mL min-1 feed solution flow rate. As a feed solution, the curcumin and the polyvinylpyrrolidone (PVP) powder were dissolved in acetone and ethanol at concentrations of 1.0 mg mL-1 and 2.0-4.0% in weight, respectively. Scanning electron microscopy (SEM) images described that most of the precipitated particle products have spherical morphologies with a size of less than 1 ?m. The Fourier transform infrared spectroscopy (FT-IR) spectra exhibited that the curcumin structural properties did not shift after the SC-CO2 antisolvent process. Moreover, the PVP addition in the curcumin particle products can enhance the curcumin dissolution in distilled water significantly.

| S-EPMC7114885 | biostudies-literature

Optimization of process parameters for preparation of polystyrene PM2.5 particles by supercritical antisolvent method using BBD-RSM.

Project description:The objective of this study is to optimize the process parameters for preparing polystyrene (PS) PM2.5 particles by supercritical antisolvent (SAS) method. Toluene was selected as the solvent and supercritical carbon dioxide (SC-CO2) was used as the antisolvent. The Box-Behnken design-response surface method was applied to investigate the effect of crystallizer pressure, PS massic concentration, flow ratio of CO2/solution and crystallizer temperature on the size and the distribution of PS particles, systematically. It is found that crystallizer temperature is the most significant variable on the size and the distribution of PS particles, followed by flow ratio of CO2/solution and PS massic concentration, and crystallizer pressure is the slightest significant factor. The particle size increases with the increase of crystallizer temperature. The optimum conditions are obtained as crystallizer pressure 9.8 MPa, PS massic concentration 1.6 wt%, flow ratio of CO2/solution 140 g/g and crystallizer temperature 309 K. Under these conditions, the PS particle with the size of 2.78 μm and a narrow size distribution has been prepared, meeting PM2.5 standard aerosols. The results suggest that it is feasible to produce PM2.5 standard aerosols by SAS.

| S-EPMC7341738 | biostudies-literature

Generation of Highly Antioxidant Submicron Particles from <i>Myrtus communis</i> Leaf Extract by Supercritical Antisolvent Extraction Process.

Project description:Submicron particles have been produced from an ethanolic extract of Myrtus communnis leaves using supercritical carbon dioxide technology, hereinafter referred to as Supercritical Antisolvent Extraction (SAE). The influence of pressure (9-20 MPa), temperature (308 and 328 K) and injection rate (3 and 8 mL/min) on the particles' precipitation has been investigated, and it has been confirmed that increases in pressure and temperature led to smaller particle sizes. The obtained particles had a quasi-spherical shape with sizes ranging from 0.42 to 1.32 μm. Moreover, the bioactivity of the generated particles was assessed and large contents of phenolic compounds with a high antioxidant activity were measured. The particles were also subjected to in vitro studies against oxidative stress. The myrtle particles demonstrated cytoprotective properties when applied at low concentrations (1 μM) to macrophage cell lines.

| S-EPMC9951993 | biostudies-literature

Novel bioactive extract from yarrow obtained by the supercritical antisolvent-assisted technique inhibits lipid metabolism in colorectal cancer.

Project description:Background: Altered lipid metabolism in cancer is associated to dissemination and prognosis. Bioactive compounds naturally occurring in Achillea millefolium L. (yarrow) have been reported to exert antitumour activities. Food biotechnology may provide on-demand mixtures of bioactive compounds with complementary activities in cancer treatment. Methods: Supercritical-antisolvent-precipitation (SAS) has been applied to fractionate the bioactive compounds from an Ultrasound-Assisted-Extraction yarrow extract resulting in two extracts with distinct polarity, yarrow-precipitate-(PP) and yarrow-separator-(Sep). Total phenolic content and relevant essential oils have been characterized. Antioxidant, anti-inflammatory and antiproliferative activities have been compared. Moreover, the effect on the inhibition of colorectal cancer cells' bioenergetics has been evaluated. Results: Yarrow-PP exerted the highest antioxidant activity, even higher than the complete UAE-yarrow extract, meanwhile yarrow-Sep showed the highest anti-inflammatory activity, even higher than the complete UAE-yarrow extract. Interestingly, yarrow-Sep inhibited key lipid metabolic targets in CRC cells extensively shown to be implicated in cancer dissemination and prognosis -SREBF1, FASN, ABCA1 and HMGCR- and epithelial to mesenchymal targets-CDH1, ATP1B1, CDH2 and Vimentin-augmenting cell adhesion. Conclusions: In summary, SAS technology has been applied to provide a novel combination of bioactive compounds, yarrow-Sep, which merits further research to be proposed as a potential complementary nutraceutical in the treatment of CRC.

| S-EPMC10991822 | biostudies-literature

The composition and friction-reducing properties of leaf layers.

Project description:Every autumn rail networks across the world suffer delays, accidents and schedule changes due to low friction problems caused by leaves landing on the rails. These leaves form a layer that can reduce the friction between the wheel and the rail to a similar level as that between ice and an ice-skate ( μ=0.01-0.05 ). Previous works have generated several hypotheses for the chemical reactions and low friction mechanism associated with these layers. In this work, the reaction between an aqueous extract of sycamore leaves and metallic iron is investigated. This reaction has been shown to produce a black precipitate, which matches field observations of leaf layers, while friction tests with these extracts produce characteristic ultra low friction. The reaction is investigated through FTIR, XPS, CHNS and ICP-MS analysis as well as wet chemical testing. The impact of the reaction on friction is investigated through three rounds of tribological testing. The results indicate that the black precipitate produced is iron tannate, formed by complexation of tannins with dissolved iron ions. Friction testing showed that eliminating tannins from the leaf extract resulted in a significant increase in the friction coefficient compared with the control.

| S-EPMC7426055 | biostudies-literature

Preparation of aripiprazole-poly(methyl vinyl ether-co-maleic anhydride) nanocomposites via supercritical antisolvent process for improved antidepression therapy

Project description:Abstract Aripiprazole (ARI), a second-generation atypical antipsychotic drug approved for schizophrenia treatment, shows good efficacy against depression. However, the poorly aqueous solubility of ARI leads to low bioavailability and increased dose-related side effects, seriously limiting its application in pharmaceutics. Herein, we demonstrated the fabrication of ARI and poly (methyl vinyl ether-co-maleic anhydride) (PVMMA) composite nanoparticles (PA NPs) using the supercritical antisolvent (SAS) process for enhancing its water-solubility and curative anti-depressant effects. Initially, the optimal experimental conditions (ARI/PVMMA mass ratio of 1:6, pressure of 10 MPa, and solution flow rate of 0.75 ml min−1) were determined by a 23 factorial experimental design, resulting in the PA NPs with an excellent particle morphology. In vitro cell experiments showed that PA NPs significantly inhibited the inflammatory response caused by the microglia activation induced by lipopolysaccharide (LPS). Similarly, mice behavioral tests demonstrated that PA NPs significantly improved LPS-induced depression-like behavior. Importantly, compared with free ARI, the LPS-induced activation of microglia in the mouse brain and the expression of inflammatory factors in serum were significantly reduced after treatment with PA NPs. Together, the innovative PA NPs designed by SAS process might provide a candidate for developing new ARI-based nano-formulations. Graphical abstract

| S-EPMC9621701 | biostudies-literature

A Retention-Matching Strategy for Method Transfer in Supercritical Fluid Chromatography: Introducing the Isomolar Plot Approach.

Project description:A strategy to match any retention shifts due to increased or decreased pressure drop during supercritical fluid chromatography (SFC) method transfer is presented. The strategy relies on adjusting the co-solvent molarity without the need to adjust the back-pressure regulator. Exact matching can be obtained with minimal changes in separation selectivity. To accomplish this, we introduce the isomolar plot approach, which shows the variation in molar co-solvent concentration depending on the mass fraction of co-solvent, pressure, and temperature, here exemplified by CO2-methanol. This plot allowed us to unify the effects of the co-solvent mass fraction and density on retention in SFC. The approach, which was verified on 12 known empirical retention models for each enantiomer of six basic pharmaceuticals, allowed us to numerically calculate the apparent retention factor for any column pressure drop. The strategy can be implemented either using a mechanistic approach if retention models are known or empirically by iteratively adjusting the co-solvent mass fraction. As a rule of thumb for the empirical approach, we found that the relative mass fraction adjustment needed is proportional to the relative change in the retention factor caused by a change in the pressure drop. Different proportionality constants were required to match retention in the case of increasing or decreasing pressure drops.

| S-EPMC8153393 | biostudies-literature

Tunable Graphene/Nitrocellulose Temperature Alarm Sensors.

Project description:Tunable temperature alarm sensors were prepared using multilayer graphene and nitrocellulose (NC) to reliably monitor early high temperature risks. The graphene/NC alarm sensor keeps in a state of electrical insulation, however, turns electrically conductive at high temperatures, such as encountering a flame attack. Its response time is limited to only a few seconds because of a quick chemical reaction of NC. The 90% graphene/NC (wt % ratio 1:9) composite alarm sensor stably remains insulated at an ambient temperature of 200 °C, resulting in a satisfactory responsive temperature (232 °C), instant response time (4.4 s), and sustained working time in the flame below the ignition temperature of most combustibles. Furthermore, the response temperature and time of the alarm sensor can be tuned by graphene/NC ratios to reduce the fire risk of various combustible materials in different fire-prone scenarios and thus has promising applications in both indoor and outdoor environments. The sensor has also proven to work in the form of paint, wallpaper, and other composites due to its superior flame retardancy property, as well as under extreme conditions (i.e., underwater and vacuum).

| S-EPMC9098115 | biostudies-literature

Supercritical Antisolvent Precipitation of Amorphous Copper-Zinc Georgeite and Acetate Precursors for the Preparation of Ambient-Pressure Water-Gas-Shift Copper/Zinc Oxide Catalysts.

Project description:A series of copper-zinc acetate and zincian georgeite precursors have been produced by supercritical CO2 antisolvent (SAS) precipitation as precursors to Cu/ZnO catalysts for the water gas shift (WGS) reaction. The amorphous materials were prepared by varying the water/ethanol volumetric ratio in the initial metal acetate solutions. Water addition promoted georgeite formation at the expense of mixed metal acetates, which are formed in the absence of the water co-solvent. Optimum SAS precipitation occurs without water to give high surface areas, whereas high water content gives inferior surface areas and copper-zinc segregation. Calcination of the acetates is exothermic, producing a mixture of metal oxides with high crystallinity. However, thermal decomposition of zincian georgeite resulted in highly dispersed CuO and ZnO crystallites with poor structural order. The georgeite-derived catalysts give superior WGS performance to the acetate-derived catalysts, which is attributed to enhanced copper-zinc interactions that originate from the precursor.

| S-EPMC5485020 | biostudies-literature

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