GC investigation of post-irradiation oxidation phenomena on polypropylene

Abstract The paper summarizes the results of research on gas products of polypropylene (PP) radiolysis. Particular attention was paid to the phenomena of post-radiation degradation of PP. The protective effect of selected aromatic compounds was investigated. The research was carried out both from the point of view of obtaining radiation-resistant PP varieties and the possibility of accelerating biodegradation phenomena, e.g., PP/cellulose composition. The phenomena of post-radiation chain oxidation of PP were investigated by gas chromatography (GC). The GC in the system used (packed column, thermal conductivity detector, argon – carrier gas) enables the determination of H2, O2, CO, and CH4 in one measurement. The samples were irradiated with electron beams (EBs) accelerated in accelerators: Elektronika 10/10 with a power of 10 kW and energy of 10 MeV and LAE 13/9 with a power of 9 kW and energy up to 13 MeV. In the tests, PP without stabilizing additives (obtained directly from the production line) and non-stabilized styrene were used. Radiolytic efficiency of hydrogen evolution allowed us to estimate the number of originally formed free radicals. The maintenance of the secondary oxidation processes was the loss of oxygen and the formation of oxidation products (CO, CH4). Attention is paid to the protective effect of aromatic compounds (polystyrene (PS), polyethylene terephthalate (PET), anthracene, fluoranthene, acenaphthene, pyrene, naphthalene) both at the stage of hydrogen atom separation and the secondary oxidation process. The examples of post-radiation oxidation of PP irradiated in cryogenic conditions (–196°C) are presented. All used aromatic compounds showed a protective effect in PP radiolysis. We suppose that this phenomenon is responsible for the charge transfer along the polymer chain from the ionization spurs to the aromatic compound. The protective ranges of PS in PP radiolysis were estimated for the variously prepared PP/PS type compositions from 6 mers to 28 mers.

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Impact of Tetrapeptide-FSEY on Oxidative and Physical Stability of Hazelnut Oil-In-Water Emulsion

Foods ◽

10.3390/foods10061400 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1400

Author(s):

Chenshan Shi ◽

Miaomiao Liu ◽

Qinghua Ma ◽

Tiantian Zhao ◽

Lisong Liang ◽

...

Keyword(s):

Particle Size ◽

Physical Stability ◽

Test System ◽

Oxidation Products ◽

Hazelnut Oil ◽

Secondary Oxidation ◽

Antioxidant Additive ◽

Water Emulsion ◽

Oil In Water ◽

Oil In Water Emulsion

This study investigates the antioxidant behaviors of a hazelnut tetrapeptide, FSEY (Phe-Ser-Glu-Tyr), in an oil-in-water emulsion. The emulsion was prepared with stripped hazelnut oil at a ratio of 10%. O/W emulsions, both with and without antioxidants (FSEY and TBHQ), were incubated at 37 °C. The chemical stabilities, including those of free radicals and primary and secondary oxidation productions, along with the physical stabilities, which include particle size, zeta-potential, color, pH, and ΔBS, were analyzed. Consequently, FSEY displayed excellent antioxidant behaviors in the test system by scavenging free lipid radicals. Both primary and secondary oxidation products were significantly lower in the FSEY groups. Furthermore, FSEY assisted in stabilizing the physical structure of the emulsion. This antioxidant could inhibit the increase in particle size, prevent the formation of creaming, and stabilize the original color and pH of the emulsion. Consequently, FSEY may be an effective antioxidant additive to use in emulsion systems.

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Evolution of α-pinene oxidation products in the presence of varying oxidizers: Negative APi-TOF point of view

10.1063/1.4803279 ◽

2013 ◽

Author(s):

Arnaud P. Praplan ◽

Siegfried Schobesberger ◽

Heikki Junninen ◽

Matti Rissanen ◽

Nina Sarnela ◽

...

Keyword(s):

Point Of View ◽

Oxidation Products

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Siliconic and Acrylic Resins Dispersed in Water as Protectives for Stone Surface

MRS Proceedings ◽

10.1557/proc-267-935 ◽

1992 ◽

Vol 267 ◽

Cited By ~ 2

Author(s):

Guido Biscontin ◽

P. Maravelaki ◽

E. Zendri ◽

A. Glisenti

Keyword(s):

Contact Angle ◽

Protective Effect ◽

Water Absorption ◽

Water Repellency ◽

Point Of View ◽

General Effect ◽

Pore Filling ◽

Complete Wetting ◽

Vapour Permeability ◽

Acrylic Resins

The aim of the present work is to compare the protective effect of solvent and water dispersed products on marble, Lecce and Istria stones. This choice is justified by the need of products effective also from the ecological and toxicological point of view. To obtain these informations two tests have been chosen: contact angle and water absorption. The contact angle may, in theory, be considered a measure of the water repellency, since complete wetting implies a contact angle of 0° and absolutely no wetting an angle of 180°. This does not apply to the water absorption by capillarity test because the absorption variation may be caused by either the water repellency action of the treatments or by the pore filling. However this test may give practical information about the general effect of the treatments. Moreover, the effect of treatments on permeability was investigated by vapour permeability test. Protective effect was studied after application of the products and at various stages of artificial weathering.

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The formation of nitro-aromatic compounds under high NO<sub><i>x</i></sub> and anthropogenic VOC conditions in urban Beijing, China

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-7649-2019 ◽

2019 ◽

Vol 19 (11) ◽

pp. 7649-7665 ◽

Cited By ~ 18

Author(s):

Yujue Wang ◽

Min Hu ◽

Yuchen Wang ◽

Jing Zheng ◽

Dongjie Shang ◽

...

Keyword(s):

Aqueous Phase ◽

Aromatic Compounds ◽

Total Concentration ◽

Fine Particulate Matter ◽

Oxidation Products ◽

Urban Atmosphere ◽

Formation Pathway ◽

Relative Contribution ◽

Phase Oxidation ◽

Nitro Aromatic

Abstract. Nitro-aromatic compounds (NACs), as important contributors to the light absorption by brown carbon, have been widely observed in various ambient atmospheres; however, their formation in the urban atmosphere was little studied. In this work, we report an intensive field study of NACs in summer 2016 at an urban Beijing site, characterized by both high-NOx and anthropogenic VOC dominated conditions. We investigated the factors that influence NAC formation (e.g., NO2, VOC precursors, RH and photolysis) through quantification of eight NACs, along with major components in fine particulate matter, selected volatile organic compounds, and gases. The average total concentration of the quantified NACs was 6.63 ng m−3, higher than those reported in other summertime studies (0.14–6.44 ng m−3). 4-Nitrophenol (4NP, 32.4 %) and 4-nitrocatechol (4NC, 28.5 %) were the top two most abundant NACs, followed by methyl-nitrocatechol (MNC), methyl-nitrophenol (MNP), and dimethyl-nitrophenol (DMNP). The oxidation of toluene and benzene in the presence of NOx was found to be a more dominant source of NACs than primary biomass burning emissions. The NO2 concentration level was found to be an important factor influencing the secondary formation of NACs. A transition from low- to high-NOx regimes coincided with a shift from organic- to inorganic-dominated oxidation products. The transition thresholds were NO2 ∼ 20 ppb for daytime and NO2∼25 ppb for nighttime conditions. Under low-NOx conditions, NACs increased with NO2, while the NO3- concentrations and (NO3-)/NACs ratios were lower, implying organic-dominated products. Under high-NOx conditions, NAC concentrations did not further increase with NO2, while the NO3- concentrations and (NO3-)/NACs ratios showed increasing trends, signaling a shift from organic- to inorganic-dominated products. Nighttime enhancements were observed for 3M4NC and 4M5NC, while daytime enhancements were noted for 4NP, 2M4NP, and DMNP, indicating different formation pathways for these two groups of NACs. Our analysis suggested that the aqueous-phase oxidation was likely the major formation pathway of 4M5NC and 3M5NC, while photo-oxidation of toluene and benzene in the presence of NO2 could be more important for the formation of nitrophenol and its derivatives. Using the (3M4NC+4M5NC) ∕ 4NP ratios as an indicator of the relative contribution of aqueous-phase and gas-phase oxidation pathways to NAC formation, we observed that the relative contribution of aqueous-phase pathways increased at elevated ambient RH and remained constant at RH > 30 %. We also found that the concentrations of VOC precursors (e.g., toluene and benzene) and aerosol surface area acted as important factors in promoting NAC formation, and photolysis as an important loss pathway for nitrophenols.

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