Journal of Supercritical Fluids最新文献

Flexible and efficient electromagnetic interference (EMI) shielding polymer composite foams are rapidly developing, but it is difficult to avoid the deterioration of shielding properties after foaming. To solve the issue, in this work, composite foams with multivariate gradient structure of thermoplastic polyurethane (TPU) mixed with multiwalled carbon nanotubes (MWCNTs) were constructed by combining the soft-hard domains proportional gradient of TPU with filler content gradient. Gradient-structured TPU/MWCNTs foams with impedance matching layer and high reflector layer were obtained and impedance matching layer with large cells significantly reduced the density while high reflector layer with a few cells maintained relatively perfect conductive network, whose shielding efficiency was 38.2 % higher than that of unfoamed sample. Furthermore, TPU/MWCNTs composite foams presented great stability even after 1000 times bending. This special multivariate gradient structure shows potential applications in microelectronic devices and aerospace fields and is critical to the development of high-performance EMI shielding polymer foams.

The production manufacture of juices generates a large amount of waste consisting mainly of fruit peels. The peels are source of molecules such as coumarins and flavonoids. In this study, the peels of Citrus limonia, Citrus deliciosa, Citrus latifolia and Citrus sinensis were the raw material for supercritical fluid extraction. The Box-Behnken design was used to optimize the global yield in function of process variables. The chemical analysis of the extract was carried out by LC-MS and GC-MS. CFD was applied to the mass and momentum conservation equations in the study of supercritical extraction using citrus peels, which allowed the determination of unknown parameters of the bidimensional mathematical model. The flavonoids, nobiletin, sinensetin and tangeretin, as well as the coumarin, citropten, were identified in all species investigated. The maximum global yield obtained were 3.93 % for Citrus limonia, 4.18 % for Citrus deliciosa, 3.48 % for Citrus latifolia and 5.32 % for Citrus sinensis.

Polymer nanocomposite foams with high electromagnetic interference (EMI) shielding performance have become the research hotspot to reduce electromagnetic wave pollution. Herein, we prepared polyethylene/poly (vinylidene fluoride)/carbon nanotubes/Fe₃O₄(PE/PVDF/Fe₃O₄/CNTs) nanocomposites and nanocomposite foams by following the simple melt blending and batch foaming procedures. The co-continuous structure system of PVDF/PE was achieved by altering the matrix ratio of PVDF/PE, while reaching a maximum average EMI shielding efficiency of ca. 28 dB for the nanocomposite with PVDF/PE ratio of 5:5. Furthermore, the largest specific EMI SE of as high as 275 dB‧cm²‧g⁻¹ was obtained for the nanocomposite foam with PVDF/PE ratio of 9: 1, in which the EMI shielding mechanism is mainly based on absorption, leading to a significantly reduction in the secondary EM wave pollution. Therefore, the preparation of porous polymer nanocomposite foams with excellent EM wave absorption performance served as a novel strategy to reduce secondary EM wave pollution that holds great potential for applications in both military and civilian fields.

The acerola non-pomace, a by-product from the juice clarification step and rich in phenolic compounds and ascorbic acid, was investigated for its biological potential through in vitro tests. Extracts were obtained using hydrothermal extraction (HT) at 121°C as well as CO₂-expanded ethanol (GXL) at 40°C. The GXL extract contained 159 mg/g of ascorbic acid, while the HT extract showed 70 mg/g. Catechin was found only in the HT extract, and quercetin only in the GXL extract. Both extracts exhibited similar antiglycemic potential, but the GXL extract showed twice the neuroprotective potential against acetylcholinesterase (AChE, IC₅₀=302 μg/mL) and lipoxygenase (LOX, IC₅₀=227 μg/mL) activities. In human breast cancer cells (MDA-MB-231), the GXL extract demonstrated better antitumor potential with an IC₅₀ of 100 μg/mL compared to 250 μg/mL for the HT extract.

Propane oxidation in supercritical water was investigated at iso-thermal iso-baric conditions using a batch reactor facility. Mixtures were comprised of 0.014 % propane by volume with an equivalence ratio of 0.8 and a total density of 222 mg/mL or 610 mg/mL. Reaction times ranged from 8 to 30 min for a temperature of 375ºC at 220 or 400 bar, or 400ºC at 220 bar. Major reaction products were CO and CO₂ and minor products were propene, acetone, ethene, ethanol, methane, methanol and hydrogen. New detailed chemical kinetic models were developed by combining and refining existing models using genetic optimization. Model predictions exhibited excellent agreement with experimental observations, and indicated that rates of H-abstraction and OH addition reactions involving alkanes and alkenes are affected by the supercritical water environment. Model accuracy was highly sensitive to the rates of CH₃O₂H = CH₃O + OH and CH₃ + H₂O₂ = CH₄ + HO₂.

Cosmetics typically contain artificial substances that could be harmful to people's health. Extended usage and exposure to these harmful substances are frequently linked to a number of negative impacts and illnesses. This study processed a Durio zibethinus rind, rich in natural antityrosinase properties, with a chemometric-assisted green extraction system. The TPC value was obtained at the optimum conditions (34.4 MPa, 62°C, and 86 min). GC-MS and FTIR spectroscopy were performed to identify the phenolic compounds and their functional group, respectively. The optimized extract contains 77 % of the mushroom tyrosinase activity. PCA shows that aspidospermidin-17-ol,1-acetyl-19,21-apoxy-15,16-dimethoxy- (AP) resembles the similar cluster with hydroquinone. COSMO-RS was used to investigate the extraction mechanism of CO₂ and AP during the SFE process. DFT and molecular docking were used to calculate the chemical reactivity and explain the tyrosinase inhibition mechanism, respectively. ADME-Tox and OSIRIS Property Explorer showed no violation of Lipinski’s rule, and toxicity with AP. In conclusion, a high-value, natural and safe cosmetic ingredient (AP) for cosmetopea was discovered using an innovative green extraction system.

This work investigated the phase behavior of the system sc-CO₂ + ethanolic extract of passion fruit bagasse (EEPFB) and the effect of operation modes on the supercritical fluid impregnation (SFI) of phenolic compounds from EEPFB in corn starch aerogels. The total reducing capacity, antioxidant capacity (FRAP and ORAC), piceatannol amount and SFI yield (%) were evaluated. Three of the four system compositions showed the formation of a solid phase. SFI in static mode provided the best TRC, FRAP, and ORAC results. There were no significant differences in the amount of piceatannol and yield (%). The nitrogen adsorption/desorption test possibly indicates the filling of the aerogel pores with EEPFB and images of the aerogel before and after SFI suggest the incorporation of phenolic compounds into the corn starch aerogels through precipitation.

Poly (butylene adipate-co-terephthalate) (PBAT) foam is a potential alternative to conventional packaging materials. However, its wide adoption is hindered by issues such as low foaming–expansion ratios and shrinkage. A series of biodegradable epoxidized cardanol (EC)-modified PBAT foams were prepared using supercritical carbon dioxide (CO₂) foaming. The addition of EC enhanced the crystallisation temperature and stiffness, and improved the rheological properties, thereby promoting polymer foamability. When the EC content reached 0.6 wt%, lightweight foams with the highest initial expansion ratio (R_v) of 48.4 were produced before shrinkage. N₂ was introduced as a co-blowing agent to reduce shrinkage of the PBAT foams, resulting in the production of a microcellular foam with a stable R_v of 12.9. EC improved the foamability of PBAT while also introducing the co-blowing agent N₂ to resist shrinkage. These findings can serve as valuable insights for the large-scale production of lightweight biodegradable foams.

Moringa oleifera L. extracts (Mo) have attracted attention as a sustainable and effective alternative to synthetic ingredients for cosmetic formulations. The unique and diverse phytochemical profile of the Mo tree enhances the quality and appeal of commercial products, as evidenced by numerous studies and patents. Supercritical carbon dioxide extraction (SFE-CO₂) is particularly advantageous for this purpose, offering enhanced thermostability and selectivity of extracted compounds compared to conventional methods. This review examines the safety and efficacy of Mo seed, leaf, and root extracts as cosmetic ingredients, focusing on their bioavailability and performance by considering the thermodynamics and operational benefits of SFE-CO₂. The collected data highlights the method’s efficiency in terms of the total extraction yield and the recovery of target compounds from Mo, providing insights from optimisation studies and linking the solvation power of supercritical CO₂ with the significant non-polar and low-polar compounds present in Mo extracts.

Supercritical cryogenic fluids exhibit significant potential for diverse applications across various industries, including liquid air energy storage, high-temperature superconducting cables, and hypersonic vehicle engine cooling. Heat transfer deterioration (HTD) poses a substantial risk to the system safety. In this study, we constructed an experimental system and performed numerical simulations to illustrate buoyancy (Bu) and thermal acceleration (Ac) effects on HTD of supercritical nitrogen (SCN₂). The newly established thresholds for buoyancy and thermal acceleration (Bu_th=1.8×10⁻⁴ and Ac_th=4.4×10⁻⁵), considering pseudo two-phase characteristics, can effectively capture buoyancy and thermal acceleration in the first and second HTD regions. The first region is influenced by the combined effect of buoyancy and thermal acceleration, while the second region is mainly influenced by thermal acceleration. The new correlations and thresholds accurately predict the occurrence of HTD and the peak position. The experimental and simulation results contribute to understanding the impact of buoyancy and thermal acceleration on SCN₂ HTD.