The influence of reaction conditions on structural properties and swelling kinetics of polyurethane hydrogels intended for agricultural purposes

2021 ◽  
pp. 105085
Author(s):  
Jelena Tanasić ◽  
Tamara Erceg ◽  
Ljiljana Tanasić ◽  
Sebastijan Baloš ◽  
Olivera Klisurić ◽  
...  
Keyword(s):  
Structural Properties ◽  
Swelling Kinetics ◽  
Reaction Conditions ◽  
Kinetics Of

Effects of salts on the kinetics of oxidation of alkenes by thallic salts in aqueous solutions

1981 ◽  
Vol 46 (3) ◽  
pp. 693-700 ◽  
Author(s):  
Milan Strašák ◽  
Jaroslav Majer
Keyword(s):  
Aqueous Solutions ◽  
Phase Transfer ◽  
Heterogeneous Reaction ◽  
Qualitative Model ◽  
Kinetic Effect ◽  
Tetraalkylammonium Salts ◽  
Reaction Conditions ◽  
Kinetics Of Oxidation ◽  
Kinetics Of ◽  
Heterogeneous Reaction Conditions

The kinetics of oxidation of alkenes by thallic sulphate in aqueous solutions, involving the two reaction steps-the hydroxythallation and the dethallation - was studied, and the effect of salts on the kinetics was examined; this made it possible to specify more precisely the reaction mechanism and to suggest a qualitative model of the reaction coordinate. It was found that in homogeneous as well as in heterogeneous reaction conditions, the reaction can be accelerated appreciably by adding tetraalkylammonium salts. These salts not only operate as catalysts of the phase transfer, but also exert a significant kinetic effect, which can be explained with a simplification in terms of a stabilization of the transition state of the reaction.

scholarly journals A Novel Pseudomonas geniculata AGE Family Epimerase/Isomerase and Its Application in d-Mannose Synthesis

Foods ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1809
Author(s):  
Zhanzhi Liu ◽  
Ying Li ◽  
Jing Wu ◽  
Sheng Chen
Keyword(s):  
3D Structure ◽  
Three Dimensional ◽  
Optimal Temperature ◽  
Reaction Conditions ◽  
Enzymatic Production ◽  
Physiological Properties ◽  
Potential Applications ◽  
Kinetics Of ◽  
Optimal Reaction ◽  
Gene Age

d-mannose has exhibited excellent physiological properties in the food, pharmaceutical, and feed industries. Therefore, emerging attention has been applied to enzymatic production of d-mannose due to its advantage over chemical synthesis. The gene age of N-acetyl-d-glucosamine 2-epimerase family epimerase/isomerase (AGEase) derived from Pseudomonas geniculata was amplified, and the recombinant P. geniculata AGEase was characterized. The optimal temperature and pH of P. geniculata AGEase were 60 °C and 7.5, respectively. The Km, kcat, and kcat/Km of P. geniculata AGEase for d-mannose were 49.2 ± 8.5 mM, 476.3 ± 4.0 s−1, and 9.7 ± 0.5 s−1·mM−1, respectively. The recombinant P. geniculata AGEase was classified into the YihS enzyme subfamily in the AGE enzyme family by analyzing its substrate specificity and active center of the three-dimensional (3D) structure. Further studies on the kinetics of different substrates showed that the P. geniculata AGEase belongs to the d-mannose isomerase of the YihS enzyme. The P. geniculata AGEase catalyzed the synthesis of d-mannose with d-fructose as a substrate, and the conversion rate was as high as 39.3% with the d-mannose yield of 78.6 g·L−1 under optimal reaction conditions of 200 g·L−1d-fructose and 2.5 U·mL−1P. geniculata AGEase. This novel P. geniculata AGEase has potential applications in the industrial production of d-mannose.

scholarly journals Polyelectrolyte Gels: A Unique Class of Soft Materials

Gels ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 102
Author(s):  
Ferenc Horkay
Keyword(s):  
Exchange Process ◽  
Interaction Strength ◽  
Soft Materials ◽  
Industrial Applications ◽  
Future Research ◽  
Swelling Kinetics ◽  
Polyelectrolyte Gels ◽  
Ion Exchange Process ◽  
Counter Ions ◽  
Kinetics Of

The objective of this article is to introduce the readers to the field of polyelectrolyte gels. These materials are common in living systems and have great importance in many biomedical and industrial applications. In the first part of this paper, we briefly review some characteristic properties of polymer gels with an emphasis on the unique features of this type of soft material. Unsolved problems and possible future research directions are highlighted. In the second part, we focus on the typical behavior of polyelectrolyte gels. Many biological materials (e.g., tissues) are charged (mainly anionic) polyelectrolyte gels. Examples are shown to illustrate the effect of counter-ions on the osmotic swelling behavior and the kinetics of the swelling of model polyelectrolyte gels. These systems exhibit a volume transition as the concentration of higher valence counter-ions is gradually increased in the equilibrium bath. A hierarchy is established in the interaction strength between the cations and charged polymer molecules according to the chemical group to which the ions belong. The swelling kinetics of sodium polyacrylate hydrogels is investigated in NaCl solutions and in solutions containing both NaCl and CaCl2. In the presence of higher valence counter-ions, the swelling/shrinking behavior of these gels is governed by the diffusion of free ions in the swollen network, the ion exchange process and the coexistence of swollen and collapsed states.

Effect of Reaction Conditions on the Kinetics of Living Isobutylene Polymerization at High Initiator/TiCl4Ratios

2000 ◽  
Vol 33 (13) ◽  
pp. 4634-4638 ◽  
Author(s):  
C. Paulo ◽  
J. E. Puskas ◽  
S. Angepat
Keyword(s):  
Reaction Conditions ◽  
Kinetics Of

Curing and swelling kinetics of new magnetorheological elastomer based on natural rubber/waste natural rubber gloves composites

2018 ◽  
Vol 51 (7-8) ◽  
pp. 583-602
Author(s):  
Nabil Hayeemasae ◽  
Hanafi Ismail
Keyword(s):  
Natural Rubber ◽  
Material Properties ◽  
Swelling Kinetics ◽  
Curing Process ◽  
Magnetorheological Elastomer ◽  
Rubber Composites ◽  
Rubber Waste ◽  
New Type ◽  
Kinetics Of ◽  
Single Filler

This article proposes a new type of magnetorheological elastomer (MRE) based on natural rubber (NR) and waste natural rubber gloves (wNRg) blends. The material properties of the MRE samples were investigated with specific focus on the curing and swelling kinetics. Two different series were prepared; the first used carbonyl iron (CI) as the single filler in the MRE, whereas the second hybridized CI with carbon black (CB) to prepare an MRE resistant to solvents. The results show that most properties depend strongly on the nature of both fillers. The higher thermal conductivity of the CI caused a substantial decrease in both the scorch and curing times and the activation energy in the curing process. Based on the diffusion study, a higher volume of fillers in the rubber composites resulted in a greater area of blockage and restricted the penetration of the solvent tested throughout the composites, irrespective of whether CI alone or in combination with CB was used in the composites.

Kinetics of Glycerol Biotransformation to Dihydroxyacetone by Immobilized Gluconobacter oxydans and Effect of Reaction Conditions

2007 ◽  
Vol 72 (9) ◽  
pp. 1269-1283 ◽  
Author(s):  
Jiří Raška ◽  
František Skopal ◽  
Karel Komers ◽  
Jaroslav Machek
Keyword(s):  
Yeast Extract ◽  
Batch Reactor ◽  
Gluconobacter Oxydans ◽  
Poly Vinyl Alcohol ◽  
Glycerol Concentration ◽  
Reaction Conditions ◽  
Extract Concentration ◽  
Autocatalytic Model ◽  
Kinetics Of ◽  
Reaction Schemes

Biotransformation of glycerol to 1,3-dihydroxyacetone was carried out in an isothermal isochoric batch reactor with Gluconobacter oxydans immobilized in poly(vinyl alcohol) gel capsules. The reaction course was described with a three-step kinetic model. Two reaction schemes were proposed and compared with 8 kinetic experiments at 25 °C. The experimental dependences of glycerol and dihydroxyacetone concentrations on reaction time were simulated very well by the autocatalytic model. The effects of reaction temperature and initial concentrations of yeast extract and glycerol were studied. Temperature 25-30 °C, initial yeast extract concentration 2-4 g l-1 and initial glycerol concentration 20-50 g l-1 were found as optimal. The determined rate constants can be used to advantage for industrial production of dihydroxyacetone from glycerol.

Effect of Elastocapillarity on the Swelling Kinetics of Hydrogels

2021 ◽  
Author(s):  
Ida Ang ◽  
Zezhou Liu ◽  
Chung Yuen Hui ◽  
Nikolaos Bouklas
Keyword(s):  
Swelling Kinetics ◽  
Kinetics Of

Kinetic Studies of Adsorption Process of Zambian Kapiri Mposhi Zeolites

2021 ◽  
Vol 37 (2) ◽  
pp. 467-475
Author(s):  
Marina G. Xavier
Keyword(s):  
Adsorption Process ◽  
Kinetic Studies ◽  
Solute Concentration ◽  
Exchange Property ◽  
Batch Adsorption ◽  
Reaction Conditions ◽  
Kinetics Of Adsorption ◽  
Calcination Temperatures ◽  
Optimum Reaction ◽  
Kinetics Of

Batch adsorption studies were done on aqueous solutions of Pb(NO3)2 at varying solute concentration, adsorbent dose, contact time, temperature, calcination temperatures and pH. Residual concentrations of the solute were found out using AAS and optimum conditions were studied. Adsorbent used in this study is locally available silicate rich mineral which closely resembles zeolites. The net negative charge on the framework of hydrated aluminosilicates is responsible for ion exchange property. Freundlich model was used to validate the results obtained from batch experiments plotting lnCe vs lnqe. Objective of this work is to study the kinetics of adsorption considering the interplay of particle diffusion in addition to proving the effectiveness as an adsorbent. A diffusion model also was also applied apart from kinetic model to analyze the experimental results more specifically. For maximizing the efficiency of the adsorption process and minimizing the time involved, variables like temperature, reactants and pH were manipulated using kinetic studies. It establishes the optimum reaction conditions for various experimental parameters in the process of adsorption.

In-vitro-digestion and swelling kinetics of whey protein, egg white protein and sodium caseinate aerogels

2020 ◽  
Vol 101 ◽  
pp. 105534 ◽  
Author(s):  
Christian Kleemann ◽  
Raffael Schuster ◽  
Elisabeth Rosenecker ◽  
Ilka Selmer ◽  
Irina Smirnova ◽  
...  
Keyword(s):  
Whey Protein ◽  
Sodium Caseinate ◽  
In Vitro Digestion ◽  
Egg White ◽  
Swelling Kinetics ◽  
Egg White Protein ◽  
Kinetics Of
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