Effects of sterically hindered N-alkoxyamines on photooxidative stability of reinforced polypropylene

e-Polymers ◽  
2012 ◽  
Vol 12 (1) ◽  
Author(s):  
Daniela Enescu ◽  
Alberto Frache
Keyword(s):  
Degradation Products ◽  
Irradiation Time ◽  
Linear Part ◽  
Oxidative Degradation ◽  
Polymer Degradation ◽  
Nitroxide Radical ◽  
Degradation Process ◽  
Peroxy Radicals ◽  
Absorption Bands ◽  
Sterically Hindered

AbstractIn the present paper the influence of Flamestab® NORTM 116 (abbrev. FNOR), a sterically hindered N-alkoxyamine stabilizer, on the photo-oxidative stability of calcium carbonate reinforced polypropylene (abbrev. CCPP) used for production of plastic collars has been investigated. The samples, prepared by melt compounding, were exposed to artificial accelerated photo-ageing carried out at λ>300 nm and 45 °C in air. FT-IR and UV-VIS analysis revealed that the deterioration of neat CCPP takes place very rapidly in comparison with the composites containing FNOR. Hydroperoxides and various carbonyl species are formed as the main degradation products during the photo-oxidation process. Moreover, the intensity of the absorption bands grows with increasing of UV exposure time indicating that the material suffers a photo-oxidative degradation process. Indeed, addition of only 0.1 wt.-% FNOR did not significantly modify the length of the induction period of neat CCPP, but a strong efficiency was obtained by increasing the amount of FNOR (0.5 wt.-%) which shows an increase of eight times more as compared with neat CCPP. Therefore, it may be supposed that OIT is linked to the level of concentration of the stabilizer. This remarkable increase in composite stability demonstrated by a lengthening of OIT is typical for sterically hindered N-alkoxyamine stabilizers since they are very efficient at scavenging freeradicals formed as the polymer degrades. In other words, these UV stabilizers are converted to nitroxide radicals (see Scheme 1) which readily trap the polymer degradation species to produce alkoxyamines. Then, the formed alkoxyamines do subsequently react with peroxy radicals to regenerate the active nitroxide radical, thereby this process (called Denisov cycle) proceed in a regenerative cycle, thus retarding oxidative polymer degradation. The increase of absorbance in the carbonyl region as a function of irradiation time was used to determinate the photooxidation rate. It was found out that the photooxidation rate measured from the slope of linear part of the curves is significantly decreased for the CCPP/FNOR 0.5 composite compared to neat CCPP. In the light of the above mentioned findings, FNOR could be taken into consideration as an UV stabilizer for CCPP.

scholarly journals Isolation and Structure Determination of Echinochrome A Oxidative Degradation Products

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4778
Author(s):  
Natalia P. Mishchenko ◽  
Elena A. Vasileva ◽  
Andrey V. Gerasimenko ◽  
Valeriya P. Grigorchuk ◽  
Pavel S. Dmitrenok ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Degradation Products ◽  
Lethal Dose ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Ionization Mass ◽  
Echinochrome A ◽  
Esi Ms

Echinochrome A (Ech A, 1) is one of the main pigments of several sea urchin species and is registered in the Russian pharmacopeia as an active drug substance (Histochrome®), used in the fields of cardiology and ophthalmology. In this study, Ech A degradation products formed during oxidation by O2 in air-equilibrated aqueous solutions were identified, isolated, and structurally characterized. An HPLC method coupled with diode-array detection (DAD) and mass spectrometry (MS) was developed and validated to monitor the Ech A degradation process and identify the appearing compounds. Five primary oxidation products were detected and their structures were proposed on the basis of high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as 7-ethyl-2,2,3,3,5,7,8-heptahydroxy-2,3-dihydro-1,4-naphthoquinone (2), 6-ethyl-5,7,8-trihydroxy-1,2,3,4-tetrahydronaphthalene-1,2,3,4-tetraone (3), 2,3-epoxy-7-ethyl-2,3-dihydro-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone (4), 2,3,4,5,7-pentahydroxy-6-ethylinden-1-one (5), and 2,2,4,5,7-pentahydroxy-6-ethylindane-1,3-dione (6). Three novel oxidation products were isolated, and NMR and HR-ESI-MS methods were used to establish their structures as 4-ethyl-3,5,6-trihydroxy-2-oxalobenzoic acid (7), 4-ethyl-2-formyl-3,5,6-trihydroxybenzoic acid (8), and 4-ethyl-2,3,5-trihydroxybenzoic acid (9). The known compound 3-ethyl-2,5-dihydroxy-1,4-benzoquinone (10) was isolated along with products 7–9. Compound 7 turned out to be unstable; its anhydro derivative 11 was obtained in two crystal forms, the structure of which was elucidated using X-ray crystallography as 7-ethyl-5,6-dihydroxy-2,3-dioxo-2,3-dihydrobenzofuran-4-carboxylic acid and named echinolactone. The chemical mechanism of Ech A oxidative degradation is proposed. The in silico toxicity of Ech A and its degradation products 2 and 7–10 were predicted using the ProTox-II webserver. The predicted median lethal dose (LD50) value for product 2 was 221 mg/kg, and, for products 7–10, it appeared to be much lower (≥2000 mg/kg). For Ech A, the predicted toxicity and mutagenicity differed from our experimental data.

scholarly journals Heat Aged Tensile Strength Retention of Poly (p-phenylene terephthalamide) Sewing Thread

2008 ◽  
Vol 3 (4) ◽  
pp. 155892500800300 ◽  
Author(s):  
Walter R. Hall ◽  
Warren F. Knoff
Keyword(s):  
Hydrolytic Degradation ◽  
Oxidative Degradation ◽  
Thermal Exposure ◽  
Strength Loss ◽  
Degradation Process ◽  
Downstream Processing ◽  
Kink Bands ◽  
Sewing Thread ◽  
Continuous Filament ◽  
Strength Retention

The strength retention after exposure to elevated temperature in air of continuous filament and staple spun PPTA sewing thread and the precursor yarns was determined. For both types, the process of converting the greige yarn to thread reduced the amount of strength retained after thermal exposure. The continuous filament products retained more strength than the staple products. The data was fitted to a kinetic rate model in which two strength loss processes occurred. The first process occurred within about the first 5 minutes of thermal exposure and is hypothesized to be hydrolytic degradation. The estimated secondary degradation process activation energy suggests this to be thermo-oxidative degradation. Optical microscopy of filaments indicates a higher level of kink banding and other damage in continuous filament versus staple products and in finished thread versus the precursor yarns. The kink bands and damage are believed to be caused by the staple manufacturing process and the downstream processing of precursor yarn to finished sewing thread. The kink bands and damage are hypothesized to be responsible for the differences in strength retention.

Chemistry of renieramycins. Part 6: Transformation of renieramycin M into jorumycin and renieramycin J including oxidative degradation products, mimosamycin, renierone, and renierol acetate

Tetrahedron ◽  
2004 ◽  
Vol 60 (17) ◽  
pp. 3873-3881 ◽  
Author(s):  
Naoki Saito ◽  
Chieko Tanaka ◽  
Yu-ichi Koizumi ◽  
Khanit Suwanborirux ◽  
Surattana Amnuoypol ◽  
...  
Keyword(s):  
Degradation Products ◽  
Oxidative Degradation

Structural Elucidation of Unknown Oxidative Degradation Products of Mycophenolate Mofetil Using LC-MSn

2016 ◽  
Vol 79 (13-14) ◽  
pp. 919-926 ◽  
Author(s):  
Ana Protić ◽  
Marina Radišić ◽  
Jelena Golubović ◽  
Biljana Otašević ◽  
Mira Zečević ◽  
...  
Keyword(s):  
Mycophenolate Mofetil ◽  
Degradation Products ◽  
Oxidative Degradation ◽  
Structural Elucidation

LC-MS-(MS) determination of oxidative degradation products of nonylphenol ethoxylates, carboxylates and nonylphenols in water

2004 ◽  
Vol 50 (5) ◽  
pp. 227-234 ◽  
Author(s):  
M. Petrovic ◽  
P. Gehringer ◽  
H. Eschweiler ◽  
D. Barceló
Keyword(s):  
Electron Beam ◽  
Electron Beam Irradiation ◽  
Limit Of Detection ◽  
Degradation Products ◽  
Oxidative Degradation ◽  
Nonylphenol Ethoxylates ◽  
Beam Irradiation ◽  
Treatment Processes ◽  
By Products

A commercial blend of nonylphenol ethoxylates (NPEOs) was chosen as representative for non-ionic polyethoxylated surfactants to study the oxidative degradation of this class of surfactants in water using ozonation as well as electron beam irradiation with and without the addition of ozone as treatment processes. The electron beam irradiation processes applied represent so-called Advanced Oxidation Processes (AOPs); the combined ozone/electron beam irradiation is, moreover, the most powerful AOP which can be applied in aqueous systems. It was found that both ozonation and the two AOPs applied were able to decompose not only the NPEOs but also the polyethyleneglycoles (PEGs) formed as by-products from NPEO degradation to residual concentrations below the limit of detection. Moreover, the treatment processes were also used to study the oxidative degradation of nonylphenoxy acetic acid (NPEC) and of nonylphenol (NP) which are formed as by-products from biodegradation of NPEOs.

scholarly journals Effect of char layer on transient thermal oxidative degradation of polyethylene

2007 ◽  
Vol 11 (2) ◽  
pp. 23-36 ◽  
Author(s):  
Javad Esfahani ◽  
Ali Abdolabadi
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Solid Phase ◽  
Early Stage ◽  
Radiation Heat Transfer ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Thermal Oxidative Degradation ◽  
Char Layer ◽  
Effect Of Oxygen

A transient one dimensional model has been presented to simulate degradation and gasification of polyethylene, in early stage of fire growth. In the present model effect of oxygen on degradation and rate of polymer gasification while the sample is subjected to an external radiative heat source is numerically investigated. This model includes different mechanism, which affect the degradation process, such as in depth thermal oxidative decomposition, in depth absorption of radiation, heat transfer, volatiles advection in solid phase and convective heat transfer on surface. Also effects of radiative parameters, due to formation of char layer such as surface reflectivity and absorptivity on thermal degradation of polyethylene are investigated. The results for 40 kW/m2 heat source are reported and yielded realistic results, comparing to the published experimental data. The results show that an increase in oxygen concentration leads to considerable increase in gasification rate and also leads to sharp increase of surface temperature. .

Oxidation of Plasmalogens Produces Highly Effective Modulators of Macrophage Function

2000 ◽  
Vol 55 (1-2) ◽  
pp. 115-120 ◽  
Author(s):  
Helmut Heinle ◽  
Nadja Gugeler ◽  
Roswitha Felde ◽  
Dagmar Okech ◽  
Gerhard Spiteller
Keyword(s):  
Degradation Products ◽  
Oxidative Degradation ◽  
Oxidative Modification ◽  
Oxygen Species ◽  
Cytotoxic Effects ◽  
Macrophage Function ◽  
Enhanced Chemiluminescence ◽  
Derivatives Of ◽  
Assay Conditions

Abstract Model derivatives of plasmalogens and chemically synthesized oxidative degradation products as found e.g. during oxidation of low density lipoproteins show strong effects on phagocytosis induced secretion of reactive oxygen species of macrophages which was measured by luminol-enhanced chemiluminescence. Whereas a plasmalogen epoxide showed enhancing effects in submicromolar range, inhibition was found with higher concentrations as well as with a-hydroxyaldehydes. The substances showed only little effects on the non-cellular ROSdependent chemiluminescence of the reaction between hydrogen peroxide and opsonized zymosan and no cytotoxic effects under the assay conditions used. These results show that oxidative modification and degradation of plasmalogens occuring also under pathophysiological situations in vivo produces effective modulators of macrophage function which could be important; e.g. during inflammation or atherogenesis.

scholarly journals RP-HPLC assay method development for Paracetamol and Lornoxicam in combination and characterization of oxidative degradation products of Lornoxicam

2013 ◽  
Vol 19 (4) ◽  
pp. 471-484
Author(s):  
Pritam Jain ◽  
Miketa Patel ◽  
Amar Chaudhari ◽  
Sanjay Surana
Keyword(s):  
Method Development ◽  
Degradation Products ◽  
Oxidative Degradation ◽  
Assay Method ◽  
Forced Degradation ◽  
Control Analysis ◽  
Reverse Phase ◽  
Solution Form ◽  
Forced Degradation Studies ◽  
Degradation Studies

A simple, specific, accurate and precise reverse phase high pressure liquid chromatographic method has been developed for the simultaneous determination of Paracetamol and Lornoxicam from tablets and to characterize degradation products of Lornoxicam by reverse phase C18 column (Inertsil ODS 3V C-18, 250 x 4.6 mm, 5 ?). The sample was analyzed using Buffer (0.02504 Molar): Methanol in the ratio of 45:55, as a mobile phase at a flow rate of 1.5 mL/min and detection at 290 nm. The retention time for Paracetamol and Lornoxicam was found to be 2.45 and 9.40 min respectively. The method can be used for estimation of combination of these drugs in tablets. The method was validated as per ICH guidelines. The linearity of developed method was achieved in the range of 249.09 - 747.29 ?g/mL (r2=0.9999) for Paracetamol and 4.0125 - 12.0375 ?g/mL (r2=0.9999) for Lornoxicam. Recoveries from tablets were between 98 and 102%. The method was validated with respect to linearity, accuracy, precision, robustness and forced degradation studies which further proved the stability-indicating power. During the forced degradation studies lornoxicam was observed to be labile to alkaline hydrolytic stress and oxidative stress (in the solution form). However, it was stable to the acid hydrolytic, photolytic and thermal stress (in both solid and solution form). The degraded products formed were investigated by electrospray ionization (ESI) time-of-flight mass spectrometry, NMR and IR spectroscopy. A possible degradation pathway was outlined based on the results. The method was found to be sensitive with a detection limit of 0.193 ?g/ml, 2.768 ?g/ml and a quantitation limit of 0.638 ?g/ml, 9.137 ?g/ml for lornoxicam and paracetamol, respectively. Due to these attributes, the proposed method could be used for routine quality control analysis of these drugs in combined dosage forms.

UV Based Advanced Oxidation Process for Degradation of Ciprofloxacin: Reaction Kinetics, Effects of Interfering Substances and Degradation Product Identification

2021 ◽  
Author(s):  
Bijoli Mondal ◽  
Shib Sankar Basak ◽  
Arnab Das ◽  
Sananda Sarkar ◽  
Asok Adak
Keyword(s):  
Organic Compounds ◽  
Advanced Oxidation Process ◽  
Oxidation Process ◽  
Uv Light ◽  
Degradation Products ◽  
Irradiation Time ◽  
Advanced Oxidation ◽  
Quantum Yields ◽  
Photon Flux ◽  
First Order

Abstract In the photochemical UV-H2O2 advanced oxidation process, H2O2 absorbs UV light and is decomposed to form hydroxyl radicals (OH·), which are highly excited and reactive for electron-rich organic compounds and hence can degrade organic compounds. In the present work, the UV-H2O2 process was investigated to degrade ciprofloxacin (CIP), one of India's widely used antibiotics, from aqueous solutions using a batch type UV reactor having photon flux = 1.9 (± 0.1) ×10-4 Einstein L-1 min-1. The effects of UV irradiation time on CIP degradation were investigated for both UV and UV-H2O2 processes. It was found that about 75% degradation of CIP was achieved within 60 s with initial CIP concentration and peroxide concentration of 10 mg L-1 and 1 mol H2O2/ mol CIP, respectively, at pH of 7(±0.1) and fluence dose of 113 mJ cm-2. The experimental data were analyzed by the first-order kinetics model to find out the time- and fluence-based degradation rate constants. Under optimized experimental conditions (initial CIP concentration, pH and H2O2 dose of 10 mg L-1, 7(±0.1) and 1.0 mol H2O2 / mol CIP, respectively), the fluence-based pseudo-first-order rate constant for the UV and UV-H2O2 processes were determined to be 1.28(±0.0) ×10-4 and 1.20(±0.04) ×10-2 cm2 mJ-1 respectively. The quantum yields at various pH under direct UV were calculated. The impacts of different process parameters such as H2O2 concentration, solution pH, initial CIP concentration, and wastewater matrix on CIP degradation were also investigated in detail. CIP degradation was favorable in acidic conditions. Six degradation products of CIP were identified. Results clearly showed the potentiality of the UV-H2O2 process for the degradation of antibiotics in wastewater.

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