DFT Study on the Chemical Degradation Mechanism of Perfluorobis(sulfonyl)imide Sulfonic Acid Ionomer Membranes

2021 ◽  
Vol 125 (3) ◽  
pp. 1929-1939
Author(s):  
Makoto Yamaguchi
Keyword(s):  
Sulfonic Acid ◽  
Degradation Mechanism ◽  
Chemical Degradation ◽  
Dft Study ◽  
Ionomer Membranes

scholarly journals Sources and sinks of acetone, methanol, and acetaldehyde in North Atlantic marine air

2005 ◽  
Vol 5 (7) ◽  
pp. 1963-1974 ◽  
Author(s):  
A. C. Lewis ◽  
J. R. Hopkins ◽  
L. J. Carpenter ◽  
J. Stanton ◽  
K. A. Read ◽  
...  
Keyword(s):  
North Atlantic ◽  
Degradation Mechanism ◽  
Chemical Degradation ◽  
Oh Radical ◽  
Detailed Model ◽  
Atmospheric Lifetime ◽  
Sources And Sinks ◽  
Marine Air ◽  
Made In

Abstract. Measurements of acetone, methanol, acetaldehyde and a range of non-methane hydrocarbons have been made in North Atlantic marine air at the Mace Head observatory. Under maritime conditions the combination of OVOCs (acetone, methanol and acetaldehyde) contributed up to 85% of the total mass of measured non methane organics in air and up to 80% of the OH radical organic sink, when compared with the sum of all other organic compounds including non-methane hydrocarbons, DMS and OH-reactive halocarbons (trichloromethane and tetrachloroethylene). The observations showed anomalies in the variance and abundance of acetaldehyde and acetone over that expected for species with a remote terrestrial emission source and OH controlled chemical lifetime. A detailed model incorporating an explicit chemical degradation mechanism indicated in situ formation during air mass transport was on timescales longer than the atmospheric lifetime of precursor hydrocarbons or primary emission. The period over which this process was significant was similar to that of airmass motion on intercontinental scales, and formation via this route may reproduce that of a widespread diffuse source. The model indicates that continued short chain OVOC formation occurs many days from the point of emission, via longer lived intermediates of oxidation such as organic peroxides and long chain alcohols.

A DFT Study on the Cyclization-Degradation Mechanism for Phenylmethylsiloxanes in Thermal Vacuum

2021 ◽  
pp. 109802
Author(s):  
Yunqiao Ding ◽  
Haifeng Lu ◽  
Qiuhong Mou ◽  
Dan Peng ◽  
MengTing Yu ◽  
...  
Keyword(s):  
Degradation Mechanism ◽  
Dft Study ◽  
Thermal Vacuum

Heat Aging Behavior of Novel Poly (Phenylene-Ether) Based Thermoplastic Elastomers

2008 ◽  
Vol 81 (2) ◽  
pp. 244-264 ◽  
Author(s):  
Samik Gupta ◽  
Radha Kamalakaran ◽  
Avdhut Maldikar ◽  
Ashok Menon ◽  
Anil K. Bhowmick
Keyword(s):  
Mechanical Properties ◽  
Thermal Degradation ◽  
Vinyl Acetate ◽  
Degradation Mechanism ◽  
Ethylene Vinyl Acetate ◽  
Thermoplastic Elastomers ◽  
Chemical Degradation ◽  
Modulated Dsc ◽  
Structure Property ◽  
Aging Performance

Abstract The heat aging performance of a series of novel poly (phenylene ether) (PPE) based thermoplastic elastomers (TPEs) from styrene-ethylene-butylene-styrene (SEBS), ethylene vinyl acetate (EVA) and PPE-polystyrene (PS), was studied. This quaternary blend showed superior heat aging performance due to the high Tg thermoplastic component (PPE). At 80 °C, different compositions of the quaternary blends were exposed for 500 hours. Effects of compositions, vinyl acetate (VA) content of EVA and different molecular weights (MW) of SEBS, on the mechanical properties upon heat aging were analyzed in detail. A representative composition (based on the mechanical properties) of the quaternary blend (SEBS/EVA/PPE-PS: 45/30/25) was exposed at different temperatures, i.e. 80 °C, 120 °C, 140 °C and 170 °C, for 2000 hours. Thermal degradation profiles of change in tensile strength and percent elongation at break due to thermal degradation of the blends were monitored and “half-life” temperature was estimated. Using the Arrhenius equation, the “lifetime” of the quaternary blend was predicted (100,000 hours at ∼131 °C). Change in functionalities due to chemical degradation was also monitored using Fourier Transform Infrared Spectroscopy (FTIR). As a consequence of degradation, the shift in Tg was observed by temperature modulated DSC (Differential Scanning Calorimeter). Detailed microstructural studies were done to establish the structure-property correlation, for degraded as well as pristine materials. The degradation mechanism was elucidated on the basis of morphology and structure studies of the blends.

A DFT study of the degradation mechanism of anticancer drug carmustine in an aqueous medium

2019 ◽  
Vol 30 (4) ◽  
pp. 1315-1321 ◽  
Author(s):  
Saba Hadidi ◽  
Farshad Shiri ◽  
Mohammadsaleh Norouzibazaz
Keyword(s):  
Aqueous Medium ◽  
Anticancer Drug ◽  
Degradation Mechanism ◽  
Dft Study
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