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.
Download full-text PDF |
Source |
---|---|
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7178296 | PMC |
http://dx.doi.org/10.3390/ma13071606 | DOI Listing |
Environ Monit Assess
December 2024
Department of Metallurgical and Material Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey.
Toxic environmental pollutants are considered to be posed a major threat to human and aquatic systems. The fast advancement of the petrochemical and chemical industries has woken up rising worries concerning the pollution of water by contaminants including phenolic Bisphenol A (BPA), an endocrine-disrupting chemical (EDC). The intermediate BPA used in synthesis of certain plastics, polycarbonate polymers, polysulfone, and epoxy resins of various polyesters.
View Article and Find Full Text PDFNeurotox Res
December 2024
Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
Chronic use of typical antipsychotics can lead to varying motor effects depending on the timing of analysis. Acute treatment typically induces hypokinesia, resembling parkinsonism, while repeated use can result in tardive dyskinesia, a hyperkinetic syndrome marked by involuntary orofacial movements, such as vacuous chewing movements in mice. Tardive dyskinesia is particularly concerning due to its potential irreversibility and associated motor discomfort.
View Article and Find Full Text PDFRecent Pat Biotechnol
December 2024
Biotechnology Process and Macromolecules Purification Laboratory, Federal University of São João del-Rei, 35501-296, Divinópolis, MG, Brazil.
Background: The increasing industrialization and hydrocarbon use have led to concerning soil contamination. Oil spills and improper disposal of oily waste pose threats to ecosystems and human health. The recovery of these environments is essential, but separating oily components from soil remains challenging.
View Article and Find Full Text PDFEnviron Health Insights
December 2024
Faculty of Health and Life Sciences, University of Exeter Medical School, University of Exeter, Exeter, UK.
The growing use of artificial turf in place of natural turf in residential, recreational and commercial settings has raised concerns regarding its potential impact on human health. A systematic review of databases revealed 5673 articles of which, 30 were deemed eligible. Those performing total concentration analyses, bioaccessibility analyses or human health risk assessments (HHRAs) of artificial turf fibres or crumb rubber infill were of interest.
View Article and Find Full Text PDFMed Lav
December 2024
Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy.
Background: PFASs, synthetic chemicals, can be encountered by humans through occupational or environmental exposure, and some reports suggest that they can disrupt endocrine and hormonal activities. In this comprehensive review and meta-analysis, we explored the connection between exposure to PFASs and the risks of breast and female genital cancers.
Methods: We systematically reviewed the literature from IARC Monographs, ATSDR documents, and PubMed (as of January 2024) for cohort, case-control, and ecological studies on PFAS exposure and breast or female genital cancers.
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!