Vulcanization of Elastomers. 46. The Kinetics of Crosslinking

1964 ◽  
Vol 37 (3) ◽  
pp. 698-708 ◽  
Author(s):  
W. Scheele ◽  
K.-H. Hillmer
Keyword(s):  
Natural Rubber ◽  
Experimental Determination ◽  
Present Article ◽  
Reaction Order ◽  
Practical Importance ◽  
Static Modulus ◽  
Working Out ◽  
Kinetics Of

Abstract The present article represents a first contribution to the investigation of the crosslinking kinetics of 1,5-polyenes, with sulfur as the vulcanizing agent. It is principally concerned with working out the pertinent methodology, and hence is a report on our experience with the “Agfa Vulcameter” (also called the Bayer Vulcameter). Using as an example the zinc benzothiazolyl mercaptide (ZnMBT)/zine stearate accelerated vulcanization of natural rubber with sulfur, which in any case runs with practically no reversion at moderate temperatures, and thus permits an experimental determination of the crosslinking end-values, we were able to show that crosslinking can be described quantitatively and qualitatively with the help of an Agfa Vulcameter. It was proved that the same reaction order and the same rates are obtained, as when the static modulus is used as the criterion for crosslinking. The scientific and practical importance of the results are pointed out.

Synthesis and Determination of the Kinetic Parameters for Non-Isothermal Decomposition of Complexes Ln(thd)3phen

2006 ◽  
Vol 530-531 ◽  
pp. 506-512 ◽  
Author(s):  
Wilton Silva Lopes ◽  
Crislene Rodrigues da Silva Morais ◽  
A.G. de Souza
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Lanthanide Complexes ◽  
Reaction Order ◽  
Decomposition Reaction ◽  
Cylindrical Symmetry ◽  
Boundary Reaction ◽  
Phase Boundary Reaction ◽  
Kinetics Of

In this work the kinetics of the thermal decomposition of two ß-diketone lanthanide complexes of the general formula Ln(thd)3phen (where Ln = Nd+3 or Tm+3, thd = 2,2,6,6- tetramethyl-3,5-heptanodione and phen = 1,10-phenantroline) has been studied. The powders were characterized by several techniques. Thermal decomposition of the complexes was studied by non-isothermal thermogravimetry techniques. The kinetic model that best describes the process of the thermal decomposition of the complexes it was determined through the method proposed by Coats-Redfern. The average values the activation energy obtained were 136 and 114 kJ.mol-1 for the complexes Nd(thd)3phen and Tm(thd)3phen, respectively. The kinetic models that best described the thermal decomposition reaction the both complexes were R2. The model R2 indicating that the mechanism is controlled by phase-boundary reaction (cylindrical symmetry) and is defined by the function g(α) = 2[1-(1-a)1/2], indicating a mean reaction order. The values of activation energy suggests the following decreasing order of stability: Nd(thd)3phen > Tm(thd)3phen.

scholarly journals Kinetika Reaksi Hidrolisis Pati Biji Alpukat (Persea americana Mill) dengan Katalis HCl

2020 ◽  
Vol 4 (1) ◽  
pp. 120-131
Author(s):  
Sitti Rahmawati ◽  
Asnila Asnila ◽  
Suherman Suherman ◽  
Paulus Hengky Abram
Keyword(s):  
Reaction Order ◽  
Second Order ◽  
Hydrolysis Reaction ◽  
Starch Hydrolysis ◽  
First Order ◽  
Graph Method ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Avocado Seed

One of the plants that can be used as raw material for making sugar is plants that contain starch content such as avocado seeds. This study aims to determine the reaction order, the reaction rate constant from the hydrolysis of avocado seed starch using HCl. The method of this research is to determine the optimum concentration of HCl hydrolysis reaction from avocado seed starch using various concentrations of HCl (0.5 M; 1 M; 1.5 M; 2 M; 2.5 M) at the optimum temperature and stirring time (90oC for 70 minute). The hydrolysis process was followed by neutralization using 5 M NaOH solution and evaporated to obtain concentrated glucose, glucose was analyzed qualitatively and quantitatively by the Benedict method and the phenol sulfuric acid method. Based on the results of the maximum glucose levels obtained from the hydrolysis of variations in the concentration of HCl avocado seed starch, HCl 1.5 M. Furthermore, determine the kinetics of the starch hydrolysis reaction using time variations (30, 40, 50, 60 and 70) minutes at 90oC and concentrations The HCl 1.5 M. reaction order is determined by the intral method and the graph method. Determination of the first order graph method is done by plotting the value of ln [A] versus time, while the second order by plotting the value of 1 / [A] versus time. The first order with a 93% confidence level was obtained from the value of R2 = 0.9312, while the second order was 85% obtained from the value of R2 = 0.8581. Determination of the order of the integral method k value tends to remain in the first order formula with an average of k = 0.01962 minutes-1. Based on the two methods, it can be determined that the kinetics of the avocado seed starch hydrolysis reaction follows a first-order reaction.

scholarly journals Kinetics of protein–ligand unbinding: Predicting pathways, rates, and rate-limiting steps

2015 ◽  
Vol 112 (5) ◽  
pp. E386-E391 ◽  
Author(s):  
Pratyush Tiwary ◽  
Vittorio Limongelli ◽  
Matteo Salvalaglio ◽  
Michele Parrinello
Keyword(s):  
Drug Design ◽  
Practical Importance ◽  
Binding Pocket ◽  
Water Molecules ◽  
The Mean ◽  
General Protein ◽  
Experimental Values ◽  
Rate Limiting ◽  
Kinetics Of

The ability to predict the mechanisms and the associated rate constants of protein–ligand unbinding is of great practical importance in drug design. In this work we demonstrate how a recently introduced metadynamics-based approach allows exploration of the unbinding pathways, estimation of the rates, and determination of the rate-limiting steps in the paradigmatic case of the trypsin–benzamidine system. Protein, ligand, and solvent are described with full atomic resolution. Using metadynamics, multiple unbinding trajectories that start with the ligand in the crystallographic binding pose and end with the ligand in the fully solvated state are generated. The unbinding rate koff is computed from the mean residence time of the ligand. Using our previously computed binding affinity we also obtain the binding rate kon. Both rates are in agreement with reported experimental values. We uncover the complex pathways of unbinding trajectories and describe the critical rate-limiting steps with unprecedented detail. Our findings illuminate the role played by the coupling between subtle protein backbone fluctuations and the solvation by water molecules that enter the binding pocket and assist in the breaking of the shielded hydrogen bonds. We expect our approach to be useful in calculating rates for general protein–ligand systems and a valid support for drug design.

Study the Polymerization Kinetics of Polyaniline by UV-Vis and HPLC and Determination of the Thermodynamic Functions using Coats-Redfern Equation from TGA Curves

2021 ◽  
pp. 4117-4121
Author(s):  
Juhaina Alghdir ◽  
Ahmad Falah ◽  
Sameh Hamo
Keyword(s):  
Thermodynamic Functions ◽  
Reaction Order ◽  
Thermal Dissociation ◽  
Temporal Stability ◽  
Sem Analysis ◽  
Order Reaction ◽  
Zero Order Reaction ◽  
Mathematical Equations ◽  
Kinetics Of

This study includes the preparation of the polyaniline at the laboratory temperature in an acidic medium. The Scanning Electron Microscopy (SEM) analysis of Polyaniline shows smooth surface and uniform nanoparticles formation with diameters of 56.4 to 90 nm. The polymerization of polyaniline kinetics was studied with two methods: UV-Vis, HPLC. Then the polymerization of polyaniline reaction order was determined and it was the zero-order reaction (n=0) in both of the previous two methods. The study of thermal dissociation indicates the temporal stability of chemicals, and study the decomposition kinetics to determine the thermodynamic functions of material disintegration. There are many methods use mathematical equations applied to TGA to study this phenomenon. The thermodynamic functions of the prepared polymers such as (G*, S*, H*) were determined based on Coats-Redfern equation from TGA curves of the compounds at each step of the disintegration.

Overall Kinetics of Natural Rubber Vulcanization at High Temperatures I—review of Investigation Techniques, Methods and Previous Results of Kinetic Analysis

1971 ◽  
Vol 44 (5) ◽  
pp. 1316-1325 ◽  
Author(s):  
R. B. Redding ◽  
D. A. Smith
Keyword(s):  
Natural Rubber ◽  
Kinetic Analysis ◽  
Kinetic Parameters ◽  
High Temperatures ◽  
Kinetic Data ◽  
Network Chain ◽  
Correct Determination ◽  
Kinetics Of ◽  
Overall Kinetics

Abstract Analysis of previously published cure data illustrates the importance of correct determination of the ultimate level of network chain density in the absence of reversion, and the correction of each kinetic data point for “reversion contributions”. A graphical procedure is described for the determination of kinetic parameters which takes these precautions into account.

Sign in / Sign up

Export Citation Format

Share Document