Studies on Thermal Oxidation Stability of Aviation Lubricating Oils

Simulating the operating condition of aviation engine via autoclave experiment of high temperature and pressure, we studied the physic-chemical property of poly-α-olefin base oil samples mixed with antioxidants of 2,6-di-tert-butyl-4-methylphenol and p,p’-diisooctyl diphenylamine at different temperature. The mechanism of degradation of PAO aviation lubricating oil was analyzed according to the oxidized products by modern analytical instruments. The results showed that the aviation lubricating oil produced a large number of low molecule compounds while increasing the temperature, and resulted in the viscosity decreasing and acid value increasing which indicated that the thermal oxidation of the oil sample underwent a radical process

Investigation of the antifungal and anti-aflatoxigenic potential of plant-based essential oils against aspergillus flavus in peanuts

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Aspergillus species are known to cause damage to food crops and are associated with opportunistic infections in humans. In the United States, significant losses have been reported in peanut production due to contamination caused by the Aspergillus species. This study evaluated the antifungal effect and anti-aflatoxin activity of selected plant-based essential oils (EOs) against Aspergillus flavus in contaminated peanuts, Tifguard, runner type variety. All fifteen essential oils, tested by the poisoned food technique, inhibited the growth of A. flavus at concentrations ranging between 125 and 4000 ppm. The most effective oils with total clearance of the A. flavus on agar were clove (500 ppm), thyme (1000 ppm), lemongrass, and cinnamon (2000 ppm) EOs. The gas chromatography-mass spectrometry (GC-MS) analysis of clove EO revealed eugenol (83.25%) as a major bioactive constituent. An electron microscopy study revealed that clove EO at 500 ppm caused noticeable morphological and ultrastructural alterations of the somatic and reproductive structures. Using both the ammonia vapor (AV) and coconut milk agar (CMA) methods, we not only detected the presence of an aflatoxigenic form of A. flavus in our contaminated peanuts, but we also observed that aflatoxin production was inhibited by clove EO at concentrations between 500 and 2000 ppm. In addition, we established a correlation between the concentration of clove EO and AFB1 production by reverse-phase high-performance liquid chromatography (HPLC). We demonstrate in our study that clove oil could be a promising natural fungicide for an effective bio-control, non-toxic bio-preservative, and an eco-friendly alternative to synthetic additives against A. flavus in Georgia peanuts

Synthesis of functional ‘polyolefins’: state of the art and remaining challenges

Functional polyolefins (i.e., polyethene or polypropene bearing functional groups) are highly desired materials, due to their beneficial surface properties. Many different pathways exist for the synthesis of these materials, each with its own advantages and drawbacks. This review focuses on those synthetic pathways that build up a polymer chain from ethene/propene and functionalised polar vinyl monomers. Despite many recent advances in the various fields of olefin polymerisation, it still remains a challenge to synthesise high molecular- weight copolymers with tuneable amounts of functional groups, preferably with consecutive insertions of polar monomers occurring in a stereoselective way. To overcome some of these challenges, polymerisation of alternative functionalised monomers is explored as well

Multifunctional poly[N-(2-hydroxypropyl)methacrylamide] copolymers via postpolymerization modification and sequential thiol–ene chemistry

Poly[N-(2-hydroxypropyl)methacrylamide] is a promising candidate material for biomedical applications. However, synthesis of functional pHPMA via compolymerization results can lead to variations in monomer composition, molar mass, and dispersity making comparison difficult. Postpolymerization modification routes, most commonly aminolysis of poly[active ester methacrylates], have alleviated some of these problems, but ester hydrolysis can lead to other problems. Here we report the synthesis of multifunctional pHPMA via a simple two-step derivatization of pHPMA homopolymer using readily available standard reagents and atom-efficient procedures. First, treatment with allyl isocyanate yields the corresponding carbamate with predictable incorporation of side-chain functionality. Allyl-pHPMA can then be derivatized further via radical thiol–ene reactions to generate pHPMA with multiple diverse functionalities but without adverse effects on the molecular weight and dispersity of the polymer. The applicability of the method to production of biologically relevant materials is demonstrated by cytocompatibility and cell labeling experiments with easily prepared ligand-functionalized pHPMA in the HCT 116 model cell line

Editorial: Lactic acid bacteria and their bioactive compounds: key regulators of gut microbiota and immune function

This Research Topic aimed to compile articles focusing on new insights into the role of lactic acid bacteria in the regulation of the gut microbiota. The main objectives included were understanding how LAB influence gut microbiota composition, identifying bioactive compounds produced by LAB and their effects, elucidating the molecular mechanisms underlying LAB\u27s impact on immunity, pathogen exclusion, and intestinal barrier function, and exploring potential therapeutic interventions involving LAB. By addressing these questions, the research was aimed to fill existing gaps in our knowledge and provide a comprehensive understanding of LAB\u27s multifaceted roles in gut health and beyond

Synthesis of poly(1-hexene)s end-functionalized with phenols

Electrophilic alkylations of phenol/2,6-dimethylphenol were performed with vinylidene-terminated poly(1-hexene)s using BF3·OEt2 catalyst. Vinylidene-terminated poly(1-hexene)s with Mn varying from 400 to 10000 were prepared by bulk polymerization of 1-hexene at 50 to -20 °C using Cp2ZrCl2/MAO catalysts. The phenol/2,6-dimethylphenol-terminated poly(1-hexene)s was characterized by NMR (1H, 13C), UV, IR and vapor phase osmometer (VPO). The isomer distribution (ortho, para and ortho/para) was determined by 13P NMR using a phosphitylating reagent, namely 2-chloro-1,3,2-dioxaphospholane. The number-average degree of functionality (Fn) > 0.9 with > 95% para selectivity could be achieved using low-molecular-weight oligomers of poly(1-hexene)s

Recent developments in the synthesis of functional poly(olefin)s

Synthesis of functional poly(olefin)s using metallocene and late transition metal catalysts resulting in poly(olefin)s having well defined functional groups either randomly distributed along the polymer chain or on chain ends is an emerging area of active interest. Such functional groups introduce some hydrophilicity in an otherwise hydrophobic poly(olefin)s as well as enable the synthesis of novel graft and block copolymers having a wide range of applications. In this review, the published literature on various approaches to the synthesis of functional poly(olefin)s, especially, terminal functional poly(olefin)s as well as block and graft copolymers will be briefly discussed

Synthesis of N-poly(alkenyl)acrylamides: a novel class of acrylamido functional macromonomers

This article does not have an abstract

Synthesis of plant-based biogenic jarosite nanoparticles using Azadirachta indica and Eucalyptus gunni leaf extracts and its application in Fenton degradation of dicamba

Bio-jarosite, an iron mineral synthesized biologically using bacteria, is a substitute for iron catalysts in the Fenton oxidation of organic pollutants. Iron nanocatalysts have been widely used as Fenton catalysts because they have a larger surface area than ordinary catalysts, are highly recyclable, and can be treated efficiently. This study aimed to explore the catalytic properties of bio-jarosite iron nanoparticles synthesized with green methods using two distinct plant species: Azadirachta indica and Eucalyptus gunni. The focus was on the degradation of dicamba via Fenton oxidation. The synthesized nanoparticles exhibited different particle size, shape, surface area, and chemical composition characteristics. Both particles were effective in removing dicamba, with removal efficiencies of 96.8% for A. indica bio-jarosite iron nanoparticles (ABFeNPs) and 93.0% for E. gunni bio-jarosite iron nanoparticles (EBFeNPs) within 120 min of treatment. Increasing the catalyst dosage by 0.1 g/L resulted in 7.6% and 43.0% increases in the dicamba removal efficiency for EBFeNPs and ABFeNPs with rate constants of 0.025 min−1 and 0.023 min−1, respectively, confirming their catalytic roles. Additionally, the high efficiency of both catalysts was demonstrated through five consecutive cycles of linear pseudo-first-order Fenton oxidation reactions