Energy Requirements of Mechanical Shear Degradation in Concentrated Polymer Solutions

1960 ◽  
Vol 33 (4) ◽  
pp. 909-920
Author(s):  
A. B. Bestul
Keyword(s):  
Activation Energy ◽  
Degradation Process ◽  
Energy Requirements ◽  
Shear Load ◽  
Molecular Weights ◽  
Shear Degradation ◽  
Carbon Carbon Bonds ◽  
Shearing Energy ◽  
Weight Decrease ◽  
Mechanical Shearing

Abstract Molecular weight decrease by mechanical shearing results when solutions of around 10% of polyisobutene having average molecular weights above 500,000 are forced through a capillary at nominal rates of shear above 10,000 sec−1. Comparison of observed plots of shear load vs. duration of shearing at fixed rates of shear during this degradation process with the corresponding estimated plots which would be expected to obtain if degradation did not occur provide a means of evaluating the amount of applied shearing energy which is dissipated by the degradation process. The result is several hundred thousand kilo-calories per mole of broken bonds, which is several thousand times the bond energy of carbon-carbon bonds. This finding is consistent with the hypothesis that whenever a bond breaks the system loses much of the free energy temporarily stored in bonds and macromolecular chains located in a comparatively large volume surrounding the broken bond, these bonds and chains having been involved in concentrating the required activation energy into the ruptured bond.

scholarly journals Superior Degradation Performance of Nanoporous Copper Catalysts on Methyl Orange

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 913
Author(s):  
Jinyi Wang ◽  
Sen Yang
Keyword(s):  
Activation Energy ◽  
Methyl Orange ◽  
High Efficiency ◽  
Low Cost ◽  
Degradation Process ◽  
Copper Catalysts ◽  
Reaction Rate Constant ◽  
Nanoporous Structure ◽  
Intra Particle Diffusion ◽  
Different Temperatures

The development of low-cost and high-efficiency catalysts for wastewater treatment is of great significance. Herein, nanoporous Cu/Cu2O catalysts were synthesized from MnCu, MnCuNi, and MnCuAl with similar ligament size through one-step dealloying. Meanwhile, the comparisons of three catalysts in performing methyl orange degradation were investigated. One of the catalysts possessed a degradation efficiency as high as 7.67 mg·g−1·min−1. With good linear fitting by the pseudo-first-order model, the reaction rate constant was evaluated. In order to better understand the degradation process, the adsorption behavior was considered, and it was divided into three stages based on the intra-particle diffusion model. Three different temperatures were applied to explore the activation energy of the degradation. As a photocatalytic agent, the nanoporous structure of Cu/Cu2O possessed a large surface area and it also had low activation energy, which were beneficial to the excellent degradation performance.

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

Molecular-beam study of the activation energy requirements for the dioxetane reaction

1978 ◽  
Vol 100 (11) ◽  
pp. 3274-3278 ◽  
Author(s):  
K. T. Alben ◽  
A. Auerbach ◽  
W. M. Ollison ◽  
J. Weiner ◽  
R. J. Cross
Keyword(s):  
Activation Energy ◽  
Molecular Beam ◽  
Energy Requirements

scholarly journals Comparative study of the reaction kinetics of three residual biomasses

BioResources ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. 2891-2905
Author(s):  
Arnaldo Martinez ◽  
Lourdes Meriño ◽  
Alberto Albis ◽  
Jorge Ortega
Keyword(s):  
Activation Energy ◽  
Heating Rate ◽  
Lignin Content ◽  
Cellulose Degradation ◽  
Calorific Value ◽  
Degradation Process ◽  
Proximate Analysis ◽  
Cellulose Content ◽  
Heating Rates ◽  
Biomass Residues

Kinetic analysis for the combustion of three agro-industrial biomass residues (coconut husk, corn husk, and rice husk) was carried out in order to provide information for the generation of energy from them. The analysis was performed using the results of the data obtained by thermogravimetric analysis (TGA) at three heating rates (10, 20, and 30 K/min). The biomass residues were characterized in terms of proximate analysis, elemental analysis, calorific value, lignin content, α-cellulose content, hemicellulose content, and holocellulose content. The biomass fuels were thermally degraded in an oxidative atmosphere. The results showed that the biomass thermal degradation process is comprised of the combustion of hemicellulose, cellulose, and lignin. The kinetic parameters of the distributed activation energy model indicated that the activation energy distribution for the pseudocomponents follows lignin, cellulose, and hemicellulose in descending order. The activation energy values for each set of reactions are similar between the heating rates, which suggests that it is independent of the heating rate between 10 K/min and 30 K/min. For all the biomass samples, the increased heating rate resulted in the overlap of the hemicellulose and cellulose degradation events.

scholarly journals DTA Evaluation of Spruce Wood Degradation Process

2017 ◽  
Vol 25 (40) ◽  
pp. 41-48
Author(s):  
Ivan Hrušovský ◽  
Peter Rantuch ◽  
Jozef Martinka ◽  
Simona Dzíbelová
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Degradation Process ◽  
Heating Rates ◽  
Wood Degradation ◽  
Wood Sawdust ◽  
Spruce Wood ◽  
Calculated Activation Energy ◽  
Two Stages ◽  
Calculated Activation

Abstract The decomposition stages of spruce wood sawdust were analyzed by means of sequential differential calorimetry. Two stages of decomposition were identified and activation energy of one stage was calculated using the Kissinger method. The DTA was conducted by means of SEDEX safety calorimeter. Sample was analyzed under three heating rates of 10, 20 and 45 °C/h in temperature range from room temperature to 400 °C. The calculated activation energy for the last and most clear decomposition peak was 122.63 KJ/mol. The results are comparable with the data calculated by J.V. Rissanen et al., who calculated activation energy for Spruce hemicellulose as 120 KJ/mol.

scholarly journals Devolatilization of African Palm (Elaeis guineensis) Husk studied by TG-MS

2018 ◽  
Vol 38 (2) ◽  
pp. 9-17
Author(s):  
Alberto Ricardo Albis Arrieta ◽  
Ever Ortiz Muñoz ◽  
Ismael Piñeres Ariza ◽  
Andrés Felipe Suárez Escobar ◽  
Marley Cecilia Vanegas Chamorro
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Mass Spectroscopy ◽  
Elaeis Guineensis ◽  
Degradation Process ◽  
Pyrolysis Process ◽  
Distributed Activation Energy Model ◽  
Evolved Gas ◽  
Secondary Reactions ◽  
Thermal Degradation Process

 Using simultaneous thermogravimetrical analysis coupled with mass spectroscopy, the pyrolysis of African palm husk, using several heat rates and programs was performed. Seven relations of mass/charge were followed of the evolved gas of the pyrolysis process, fitting the kinetics and the mass spectroscopy signals to the distributed activation energy model (DAEM) with different numbers of pseudo-components. Fitting with four pseudo-components proved to be the best for modeling the thermal degradation process. Kinetic parameters were not affected by the heating rate or program employed, which agrees with other reports for similar biomass. Methane, methanol formaldehyde, furfural were successfully fitted to the DAEM model, nevertheless CO2 and NO2 were not able to be represented by this model due to its production in secondary reactions in gaseous phase.

Thermal Behavior of Polychlal Fiber Modified with Phosphorus Oxychloride

1992 ◽  
Vol 10 (4) ◽  
pp. 323-334 ◽  
Author(s):  
Kazuhiko Fukatsu
Keyword(s):  
Activation Energy ◽  
Weight Loss ◽  
Thermogravimetric Analysis ◽  
Thermal Behavior ◽  
Phosphorus Oxychloride ◽  
Degradation Kinetics ◽  
Degradation Process ◽  
Rapid Weight Loss ◽  
Maximum Activation ◽  
Thermal Degradation Process

The thermal behavior of polychlal fiber partially phosphorylated with phosphorus oxychloride has been studied using a conventional dynamic thermogravimetric technique. The dynamic thermogravimetric analysis curves have been analyzed using analytical methods reported in the literature to obtain information about the sequential stages in the thermal degradation process. The data obtained reveals that the phosphorus system is capable of modifying the degradation kinetics, with the phosphorylated polychlal fiber having a reduced maximum activation energy and more rapid weight loss dur ing the initial degradation.

scholarly journals Structural Characterization, Antioxidant Activity, and Biomedical Application of Astragalus Polysaccharide Degradation Products

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Jian-Min Wang ◽  
Xin-Yuan Sun ◽  
Jian-Ming Ouyang
Keyword(s):  
Molecular Weight ◽  
Antioxidant Activity ◽  
Biomedical Application ◽  
Degradation Products ◽  
Human Kidney ◽  
Degradation Process ◽  
Chain Structure ◽  
Molecular Weights ◽  
Reducing Ability

To study the antioxidant capacity of Astragalus polysaccharides (APS) with different molecular weights, we used hydrogen peroxide to degrade original Astragalus polysaccharide (APS0) with an initial molecular weight of 11.03 kDa and obtained three degraded polysaccharides with molecular weights of 8.38 (APS1), 4.72 (APS2), and 2.60 kDa (APS3). The structures of these polysaccharides were characterized by 1H NMR, 13C NMR, FT-IR, and GC/MS. The degradation process did not cause significant changes in the main chain structure of APS. The monosaccharide component of APS before and after degradation was slightly changed. The antioxidant ability in vitro (removing hydroxyl and ABTS radicals and reducing ability) and in cells (superoxide dismutase and malondialdehyde generation) of these polysaccharides is closely related to their molecular weight. If the molecular weight of APS is very high or low, it is not conducive to their activity. Only APS2 with moderate molecular weight showed the greatest antioxidant activity and ability to repair human kidney epithelial (HK-2) cells. Therefore, APS2 can be used as a potential antistone polysaccharide drug.

The Effect of Intumescent Flame Retardant Contained Microencapsulated Red Phosphorus on the Flame Retardance and Thermal Degradation Behaviour of Epoxy Resin

2011 ◽  
Vol 197-198 ◽  
pp. 1167-1170
Author(s):  
Zhi Ping Wu ◽  
Yun Chu Hu ◽  
Mei Qin Chen
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Flame Retardant ◽  
Epoxy Resin ◽  
Flame Retardants ◽  
Degradation Process ◽  
Intumescent Flame Retardant ◽  
Flame Retardance ◽  
Red Phosphorus ◽  
Degradation Behaviour

The effect of intumescent flame retardant (IFR) contained microencapsulated red phosphorus on the flame retardance of E-44 epoxy resin (EP) was studied. The test results indicated that good flame retardancy can be realized when epoxy resin treated with 30% IFR. Thermogravimetric analysis showed that the charring amount at high temperature of EP can increase substantially when IFR was incorporated. In order to further explain this phenomenon, Dolye integration method of thermal degradation dynamics was employed to study the thermal degradation process of EP treated with IFR based on the microencapsulated red phosphrous according to the thermal gravimetry analysis results.The activation energy and reactor order of different thermal degradation stages were obtained. The results of thermal degradation dynamics implied the intumescent flame retardants can improve the flame retardance of the epoxy resin through decrease the degradation speed and increase the activation energy of the second thermal degradation stage.

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