scholarly journals Effect of Temperature on the Chemical Composition and Physicochemical Properties of Diester Aviation Lubrication Oil

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Ting Yao ◽  
Na Zhang ◽  
Jianqiang Hu ◽  
Xiaoxiao Liao ◽  
Yongli Shen ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Physicochemical Properties ◽  
Degradation Mechanism ◽  
Oxidation Stability ◽  
Lubricating Oil ◽  
Effect Of Temperature ◽  
Gas Chromatography Mass Spectrometry ◽  
Low Molecular Weight ◽  
Chemical Compositions ◽  
Main Process

High temperature is the main factor responsible for degrading the lubrication and antiwear properties of aero-lubricating oils. Accordingly, this study assessed the effects of thermal treatment of diester aviation lubricating oil and the associated mechanism. Fourier-transform infrared spectroscopy and gas chromatography/mass spectrometry analyses showed that low-molecular-weight compounds, such as monoesters, diesters, alcohols, and olefins, were the primary degradation products. An assessment of the degradation mechanism of bis(2-ethylhexyl)decanedioate showed that pyrolysis, resulting in the cleavage of β-C–H and C–C bonds, was the main process involved. Additional investigation using advanced polymer chromatography showed that the molecular weights of oil samples changed slightly at high temperatures, while the viscosity and viscosity-temperature index values were relatively stable. High-pressure differential scanning calorimetry established that the thermal oxidation stability of these oils decreased above 250°C. Finally, variations in the chemical compositions of the oil samples were found to be highly correlated with changes in physicochemical properties during thermal processing, with the formation of low-molecular-weight polar compounds greatly increasing the acid numbers of the oils.

scholarly journals Effect of Temperature on the Composition of a Synthetic Hydrocarbon Aviation Lubricating Oil

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1606 ◽  
Author(s):  
Zhuoting Gan ◽  
Ting Yao ◽  
Meng Zhang ◽  
Jianqiang Hu ◽  
Xiaoxiao Liao ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Pour Point ◽  
Kinematic Viscosity ◽  
Molecular Level ◽  
Acid Number ◽  
Lubricating Oil ◽  
Effect Of Temperature ◽  
Gas Chromatography Mass Spectrometry ◽  
Chemical Compositions ◽  
Synthetic Hydrocarbon

Synthetic hydrocarbon aviation lubricating oils (SHALOs) gradually degrade over time when subjected to high temperatures, resulting in their composition and properties varying over the operation lifetime. Therefore, understanding the SHALO degradation properties by elucidating the mechanism on a molecular level, as a function of high temperature, is of interest. A SHALO was subjected to thermal treatment (TT) at 180, 200, 230, 250, 270, or 300 °C for 2 h. The chemical compositions of six TT samples and one fresh oil were analyzed by fourier transform infrared F spectroscopy, advanced polymer chromatography, and gas chromatography/mass spectrometry. Furthermore, the physicochemical properties, such as kinematic viscosity, pour point, and acid number, of seven samples were determined. The oil samples were grouped by cluster analysis (CA) using a statistical method. The SHALO was identified to comprise 20 functional groups, including comb-like alkanes, long-chain diesters, amines, phenols, and other compounds. TT at <230 °C caused partial cracking of the SHALO base oils, with a concomitant change in the antioxidant content and type, and the polycondensation reactions were dominant. The observed antioxidant changes were not obvious from TT at >230 °C. A large number of small-molecule compounds were detected, including n-alkanes and olefins. TT at 250 °C was shown to be an important threshold for the kinematic viscosity, pour point, and acid number of the samples. Below 250 °C, the sample properties were relatively stable; but at elevated TT temperatures (>250 °C), the properties were observed to dramatically degrade. As the sample color was highly sensitive to temperature, the TT temperature induced rapid and significant color changes. The CA analysis results for the oil compounds at the molecular level were in good agreement with observed changes in the physicochemical properties at the macro level.

scholarly journals Low-Molecular-Weight Heparins: Reduced Size Particulate Systems for Improved Therapeutic Outcomes

Molecules ◽  
2018 ◽  
Vol 23 (7) ◽  
pp. 1757 ◽  
Author(s):  
Fahad Akhtar ◽  
Xinyu Wan ◽  
Gang Wu ◽  
Samuel Kesse ◽  
Shaoda Wang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Physicochemical Properties ◽  
Review Article ◽  
Nano Particles ◽  
Low Molecular Weight ◽  
Low Molecular Weight Heparins ◽  
Drug Of Choice ◽  
Therapeutic Outcomes ◽  
Efficient Delivery ◽  
Wide Range

A wide range of diseases have been treated using low-molecular-weight heparins (LMWHs), the drug of choice for anticoagulation. Owing to their better pharmacokinetic features compared to those of unfractionated heparin (uFH), several systems incorporating LMWHs have been investigated to deliver and improve their therapeutic outcomes, especially through development of their micro- and nano-particles. This review article describes current perspectives on the fabrication, characterization, and application of LMWHs-loaded micro- and nano-particles to achieve ameliorated bioavailability. The valuable applications of LMWH will continue to encourage researchers to identify efficient delivery systems that have specific release characteristics and ameliorated bioavailability, overcoming the challenges presented by biological obstructions and the physicochemical properties of LMWHs.

scholarly journals Effect of Polysaccharide Sources on the Physicochemical Properties of Bromelain–Chitosan Nanoparticles

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1681 ◽  
Author(s):  
Janaína Artem Ataide ◽  
Eloah Favero Gérios ◽  
Letícia Caramori Cefali ◽  
Ana Rita Fernandes ◽  
Maria do Céu Teixeira ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Physicochemical Properties ◽  
Enzyme Stability ◽  
Proteolytic Enzymes ◽  
Chitosan Nanoparticles ◽  
Low Molecular Weight ◽  
Chitosan Oligosaccharide ◽  
Nanoparticle Suspension ◽  
Accelerated Stability ◽  
Low Molecular Weight Chitosan

Bromelain, a set of proteolytic enzymes potential pharmaceutical applications, was encapsulated in chitosan nanoparticles to enhance enzyme stability, and the effect of different chitosan sources was evaluated. Chitosan types (i.e., low molecular weight chitosan, chitosan oligosaccharide lactate, and chitosan from shrimp shells) produced nanoparticles with different physicochemical properties, however in all cases, particle size and zeta potential decreased, and polydispersity index increased after bromelain addition. Bromelain encapsulation was higher than 84% and 79% for protein content and enzymatic activity, respectively, with low molecular weight chitosan presenting the highest encapsulation efficiency. Nanoparticle suspension was also tested for accelerated stability and rheological behavior. For the chitosan–bromelain nanoparticles, an instability index below 0.3 was recorded and, in general, the loading of bromelain in chitosan nanoparticles decreased the cohesiveness of the final suspension.

Physicochemical properties of low molecular weight alkylated chitosans: A new class of potential nonviral vectors for gene delivery

2006 ◽  
Vol 51 (2) ◽  
pp. 140-148 ◽  
Author(s):  
Sebnem Ercelen ◽  
Xin Zhang ◽  
Guy Duportail ◽  
Christian Grandfils ◽  
Jacques Desbrières ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Gene Delivery ◽  
Physicochemical Properties ◽  
Low Molecular Weight ◽  
Nonviral Vectors ◽  
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