scholarly journals Degradation Behavior of Polypropylene during Reprocessing and Its Biocomposites: Thermal and Oxidative Degradation Kinetics

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1627
Author(s):  
Elnaz Esmizadeh ◽  
Costas Tzoganakis ◽  
Tizazu H. Mekonnen
Keyword(s):  
Degradation Kinetics ◽  
Oxidative Degradation ◽  
High Volume ◽  
Degradation Process ◽  
Chain Scission ◽  
Secondary Process ◽  
Melt Flow Rate ◽  
Accelerated Degradation ◽  
Batch Mixing ◽  
Product Manufacturing

Non-isothermal thermogravimetric analysis (TGA) was employed to investigate the degradation of polypropylene (PP) during simulated product manufacturing in a secondary process and wood–plastic composites. Multiple batch mixing cycles were carried out to mimic the actual recycling. Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW), Friedman, Kissinger and Augis models were employed to calculate the apparent activation energy (Ea). Experimental investigation using TGA indicated that the thermograms of PP recyclates shifted to lower temperatures, revealing the presence of an accelerated degradation process induced by the formation of radicals during chain scission. Reprocessing for five cycles led to roughly a 35% reduction in ultimate mixing torque, and a more than 400% increase in the melt flow rate of PP. Ea increased with the extent of degradation (α), and the dependency intensified with the reprocessing cycles. In biocomposites, despite the detectable degradation steps of wood and PP in thermal degradation, a partial coincidence of degradation was observed under air. Deconvolution was employed to separate the overlapped cellulose and PP peaks. Under nitrogen, OFW estimations for the deconvoluted PP exposed an upward shift of Ea at the whole range of α due to the high thermal absorbance of the wood chars. Under air, the Ea of deconvoluted PP showed an irregular rise in the initial steps, which could be related to the high volume of evolved volatiles from the wood reducing the oxygen diffusion.

scholarly journals Kinetics of Micellar Effect of Non-Ionic Surfactant on Oxidative Degradation of Ciprofloxacin

2019 ◽  
Vol 32 (2) ◽  
pp. 359-368
Author(s):  
Ajaya Kumar Singh ◽  
Alpa Shrivastava ◽  
Dilip R. Shrivastava ◽  
Rajmani Patel ◽  
Neerja Sachdev
Keyword(s):  
Degradation Kinetics ◽  
Oxidative Degradation ◽  
Activation Parameters ◽  
Solvent Polarity ◽  
Degradation Process ◽  
Oxidation Products ◽  
Ionic Surfactant ◽  
Reaction Conditions ◽  
Chloramine T ◽  
Kinetics Of

Oxidative degradation kinetics of leading fluoroquinolone family drug ciprofloxacin (CIP) by chloramine-T (CAT) in TX-100 micelle media was studied spectrophotometrically at 275 nm and 298 K. In pseudo-first-order conditions the rate constant (kobs) decreased regularly with increasing [TX-100]. To understand the self-organizing activities of TX-100, CMC values in varying reaction conditions had been evaluated. The role of non-ionic surfactant in the oxidative degradation process of ciprofloxacin by chlorinating agent chloramine-T is explained in terms of mathematical model explained by Menger-Portnoy. The reaction showed first to zero order dependence on [CAT] and fractional order on [CIP]. Increasing [H+] decreased the rate of reaction. The effect of ionic strength and solvent polarity of the medium in reaction conditions were studied. The effects of added salts [HSO4Na], [KCl], [KNO3] and [K2SO4] had also been studied. The stoichiometry of the reaction determined was 1:2 and the oxidation products were identified by LC-EI-MS. The analysis of degradation product of ciprofloxacin evidently reveals that the piperazine moiety is active site for oxidation in the reaction. Activation parameters were studied to propose appropriate mechanism for the reaction.

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.

Non-isothermal degradation kinetics for polycarbonate/ polymethylphenylsilsesquioxane composites

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Jiangbo Wang ◽  
Zhong Xin
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Flame Retardancy ◽  
Degradation Kinetics ◽  
Degradation Process ◽  
Nitrogen Atmosphere ◽  
Ozawa Method ◽  
Degradation Behaviors ◽  
Thermal Degradation Process

AbstractThe thermal degradation behaviors of PC/PMPSQ (polymethylphenylsilsesquioxane) systems were investigated by thermogravimetric analysis (TGA) under non-isothermal conditions in nitrogen atmosphere. During non-isothermal degradation, Kissinger and Flynn-Wall-Ozawa methods were used to analyze the thermal degradation process. The results showed that a remarkable decrease in activation energy ( E ) was observed in the early and middle stages of thermal degradation in the presence of PMPSQ, which indicated that the addition of PMPSQ promoted the thermal degradation of PC. Flynn-Wall-Ozawa method further revealed that PMPSQ significantly increased the activation energy of PC thermal degradation in the final stage, which illustrated that the PMPSQ stabilized the char residues and improved the flame retardancy of PC in the final period of thermal degradation process

Characterization and thermal degradation kinetics of thermoplastic polyimide based on BAPP

2017 ◽  
Vol 30 (7) ◽  
pp. 787-793 ◽  
Author(s):  
Xu Su ◽  
Yong Xu ◽  
Linshuang Li ◽  
Chaoran Song
Keyword(s):  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Degradation Process ◽  
Thermal Degradation Kinetics ◽  
Heating Rates ◽  
Step Method ◽  
Nitrogen Derivative ◽  
Degradation Reaction ◽  
Kinetics Of

Two kinds of thermoplastic polyimides (PIs) were synthesized via a two-step method with 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4′-oxydianiline (ODA) diamine, and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), and their thermal degradation kinetics was studied by thermogravimetric analysis at different heating rates under nitrogen. Derivative thermogravimetric analysis curves indicated a simple, single-stage degradation process in PI BTDA-BAPP and a two-stage degradation process in PI BTDA-ODA-BAPP. The activation energies ( Eas) of the thermal degradation reaction were determined by the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods without a knowledge of the kinetic reaction mechanism. By comparing the values of Ea and weight loss temperatures, it was demonstrated that the thermal stability of PI BTDA-ODA-BAPP was superior to that of PI BTDA-BAPP.

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. .

scholarly journals Reaction of a satirically hindered iron(III) porphyrin with peroxyacetic acid: Degradation kinetics

2005 ◽  
Vol 70 (8-9) ◽  
pp. 1105-1111 ◽  
Author(s):  
P. Prakash ◽  
Mary Francisca
Keyword(s):  
Reaction Mechanism ◽  
Spectroscopic Study ◽  
Kinetic Analysis ◽  
Peracetic Acid ◽  
Degradation Kinetics ◽  
Oxidative Degradation ◽  
Peroxyacetic Acid ◽  
Porphyrin Ligand ◽  
Uv Visible ◽  
Reversible Formation

A kinetic analysis of the reaction between peracetic acid (AcOOH), and tetrakis (pentafluorophenyl) - 21H, 23H-porphine iron(III) chloride Fe(F20TPP)Cl, in acetonitrile showed that the peracetic acid oxidatively destroys Fe(F20TPP)Cl. This is in contrast to an assumption that the oxidative degradation of metalloporphyrins can be prevented by the introduction of electron-withdrawing substituents into the phenyl groups of the porphyrin ligand. A UV-visible spectroscopic study showed a degree of macro cycle destruction of the tetrapyrrole conjucation of the metalloporphyrin. The degradation takes place via oxoperferryl species. The first step of the reaction mechanism is the reversible formation of an adduct ?X? (k1/k-1) between Fe(F20TPP)Cl and peracetic acid, followed by an irreversible step (k2) for the formation of oxoperferryl species.

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.

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