Simulation and Verification for Sulfur Accelerated Vulcanization of Gum Natural Rubber Compound

2002 ◽  
Vol 75 (2) ◽  
pp. 287-297 ◽  
Author(s):  
Ru-liang Fan ◽  
Yong Zhang ◽  
Chen Huang ◽  
Peng Gong ◽  
Yin-xi Zhang
Keyword(s):  
Natural Rubber ◽  
Rate Constants ◽  
Arrhenius Equation ◽  
Kinetic Scheme ◽  
Activation Energies ◽  
Simulation Process ◽  
Swelling Equilibrium ◽  
Wide Range ◽  
Different Temperatures ◽  
Good Agreement

Abstract A simplified and realistic kinetic scheme was proposed for the cure reversion mechanism of accelerated sulfur vulcanization for gum natural rubber (NR) compounds. The vulcametric curves at different temperatures were simulated from curing to overcuring periods by using a kinetic approach. The different rate constants and activation energies were calculated from the simulation process. The simulated results showed a good agreement with isothermal vulcametric data over a wide range of temperatures and showed that the relationships between the rate constants and the cure temperatures were in accordance with the Arrhenius Equation. The activation energies (Ea1, Ea2, and Ea3) of the formation, desulfurization and decomposition of polysulfidic crosslink obtained from Arrhenius plots were 79.5,102.6 and 138.8 kJ/mol, respectively. The experimentally measured crosslink densities determined by using swelling equilibrium and chemical probe techniques agreed with the simulated vulcametric curves to some extent.

Studies of the Vulcanization of Elastomers. VIII. The Vulcanization of Synthetic Rubbers with Thiuram Disulfides (1)

1957 ◽  
Vol 30 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Walter Scheele ◽  
Horst-Eckart Toussaint
Keyword(s):  
Natural Rubber ◽  
Quantitative Study ◽  
Rate Constants ◽  
Activation Energies ◽  
First Order ◽  
Wide Range ◽  
Tetraethylthiuram Disulfide

Abstract The vulcanization of Buna S-3 by tetraethylthiuram disulfide is reported. A quantitative study of the transformation reactions led to the following results. (1) Using tetraethylthiuram disulfide as representative of the class, it was found that two thirds of it undergoes transformation to zinc dithiocarbamate during the vulcanization of Buna S-3, independent of the temperature. (2) Both the decrease of thiuram disulfide and increase of dithiocarbamate are first-order reactions within a wide range of the transformation. (3) The rate constants of the decrease of thiuram and of the increase of dithiocarbamate are a little less than a tenth power greater than for the vulcanization of natural rubber. This is possibly explainable by the different structure of the allyl units in Buna S-3. (4) The activation energies of the decrease of thiuram as well as the increase of dithiocarbamate are nearly the same and are greater than for the vulcanization of natural rubber.

Measurement of the loss tangent of low-density polyethylene with a nanoindentation technique

2000 ◽  
Vol 15 (5) ◽  
pp. 1195-1198 ◽  
Author(s):  
J. L. Loubet ◽  
W. C. Oliver ◽  
B. N. Lucas
Keyword(s):  
Loss Tangent ◽  
Arrhenius Equation ◽  
Viscoelastic Behavior ◽  
Low Density ◽  
Diamond Indenter ◽  
Different Temperatures ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
Two Temperatures ◽  
Good Agreement

This paper describes experimental measurements of the linear viscoelastic behavior of the surface of low-density (LD) polyethylene in contact with a pyramidal Berkovich diamond indenter. The experiments were carried out at two different temperatures, 15.9 and 27.2 °C, between frequencies of 0.1 and 800 Hz. Using the shift of the loss tangent between the two temperatures at frequencies lower than 20 Hz and an Arrhenius equation, an activation energy of 105 ± 2 kJ/mol was obtained. This value is in good agreement with the bulk value of the a relaxation of LD polyethylene reported in the literature.

scholarly journals Electrical Transport properties of Ni-Cr binary alloys

2014 ◽  
Vol 24 (2) ◽  
pp. 135
Author(s):  
P. H. Suthar ◽  
B. Y. Thakore ◽  
P. N. Gajjar
Keyword(s):  
Transport Properties ◽  
Electrical Transport ◽  
Binary Alloys ◽  
Correlation Effect ◽  
Model Potential ◽  
Electrical Transport Properties ◽  
Wide Range ◽  
Different Temperatures ◽  
Cr Concentration ◽  
Good Agreement

Electrical transport properties viz. electrical resistivity and thermal conductivity of Ni-Cr binary alloys are determine by our recognized single parametric model potential in wide range of Cr concentration. In this work, screening functions (Ichimaru and Utsumi, Farid et al. and Sarkar et al.) are employed along with the Hartree and Taylor functions to study the relative influence of the exchange and correlation effect. Given liquid alloys are studied as a function of their composition at three different temperatures according to Faber-Ziman model. Computed values of electrical transport properties are in good agreement with the experimental data available in literature.

Thermal isomerizations of protonated bicyclo[3.1.0]hexenones

1988 ◽  
Vol 66 (6) ◽  
pp. 1350-1354 ◽  
Author(s):  
Ronald F. Childs ◽  
Baha E. George
Keyword(s):  
Rate Constants ◽  
Ring Opening ◽  
Strong Acid ◽  
Activation Energies ◽  
Thermal Isomerization ◽  
The Other ◽  
Triflic Acid ◽  
Wide Range

The thermal isomerization of a wide range of protonated methyl substituted bicyclo[3.1.0]hex-3-en-2-ones to protonated phenols has been examined using triflic acid as a strong acid solvent. The rate constants and activation energies of these isomerizations have been determined. The barriers to the isomerizations were shown to be dependent on the number and position of the methyl substituents. The results show that three different mechanisms are needed to account for these isomerizations, two of which involve a preliminary circumambulatory rearrangement prior to ring opening and the other process involving a direct ring opening of the initial protonated bicyclohexenone to give an intermediate meta-protonated phenol.

Temperature Dependent Optical Response of Si(100): Theory vs. Experiment

2011 ◽  
Vol 1370 ◽  
Author(s):  
A.I. Shkrebtii ◽  
J. Heron ◽  
J.L. Cabellos ◽  
N. Witkowski ◽  
O. Pluchery ◽  
...  
Keyword(s):  
Optical Response ◽  
Layer By Layer ◽  
Temperature Dependent ◽  
Reflectance Anisotropy ◽  
Surface Optical ◽  
Wide Range ◽  
Different Temperatures ◽  
Linear Optical Properties ◽  
First Time ◽  
Good Agreement

ABSTRACTWe investigate theoretically and experimentally the temperature-dependent linear optical properties of the clean c(4×2) reconstructed Si(100) surface for a wide range of temperatures. We combine two theoretical formalisms: the first one incorporates the contribution of temperature-dependent atomic motion to the surface optical response and, the second uses a dielectric function layer-by-layer separation method. Using these formalisms, we model temperature-dependent reflectance anisotropy (RA) of this surface for the first time: finite temperature ab-initio Car-Parrinello Molecular Dynamics (CPMD) at different temperatures up to 1000 K provide temperature-dependent atomic structural inputs for optical calculations and subsequent average of dielectric functions. Experimentally, one-domain c(4x2) Si(100) surface was prepared and characterised by Reflectance Anisotropy Spectroscopy (RAS) in a temperature range between 300 K and 800 K. Good agreement between experiment and theory is demonstrated, including a temperature-induced red shift of both the surface and bulk optical peaks. Theoretical results indicate that the temperature-induced modification of the optical response is substantially more pronounced for the surface than for the bulk.

The Effect of Carbon Black Type on the Dynamic Properties of Natural Rubber

1973 ◽  
Vol 46 (4) ◽  
pp. 897-926 ◽  
Author(s):  
J. D. Ulmer ◽  
V. E. Chirico ◽  
C. E. Scott
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Surface Area ◽  
Strain Amplitude ◽  
Dynamic Properties ◽  
Dynamic Strain ◽  
Rubber Compound ◽  
Wide Range ◽  
Frequency Interaction ◽  
Different Temperatures

Abstract The influence of carbon black type on the dynamic properties of natural rubber is examined for nine carbon blacks, encompassing a wide range of structure and surface area. The dynamic properties are measured at 23° C and 100° C, over a 2 decade range of log frequency, and over a range of 1 to 25 per cent dynamic strain. The effect of carbon black structure and surface area on dynamic properties of a natural rubber compound are dependent on the combination of strain amplitude and frequency test conditions. The effect of carbon black surface area and structure at different temperatures varies on an absolute basis but not necessarily on a relative basis. Correlations of forced non resonant measurements of dynamic properties with dynamic measurements using other instruments confirms the strain amplitude and frequency interaction with carbon black type. Also, the Goodyear-Healy Rebound machine, the Goodrich Flexometer, and the Pirelli Hysteresimeter can be used to estimate basic dynamic properties over limited strain amplitude and frequency conditions. In addition, mixing procedure was found to have a significant effect on the dynamic properties of a natural rubber compound filled with N-327.

scholarly journals Tensile Behavior of Acrylonitrile Butadiene Styrene at Different Temperatures

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jiquan Li ◽  
Yadong Jia ◽  
Taidong Li ◽  
Zhou Zhu ◽  
Hangchao Zhou ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Glassy State ◽  
Quantitative Relationship ◽  
Acrylonitrile Butadiene Styrene ◽  
Tensile Behavior ◽  
Fitting Method ◽  
Wide Range ◽  
Different Temperatures ◽  
Good Agreement ◽  
Butadiene Styrene

Temperature greatly influences the mechanical response of acrylonitrile butadiene styrene (ABS). The tensile behavior of ABS was explored in this study. The tensile experiments were conducted at a wide range of temperatures (from 40°C to 130°C). A model was established to reveal the quantitative relationship between temperature and tensile behavior of ABS. The results of tensile experiments showed that tensile behavior of ABS exhibited glassy state and high-elastics state. The model was also divided into two parts that rely on the boundary of glass transition temperature, in which the parameters of the model were calculated by the fitting method. The model predictions showed a good agreement with the results of the experimental tensile test. This study provides the quantitative relationship between temperature and tensile behavior of ABS, which saves time and experimental costs.

Computational Study on the Kinetics and Mechanisms of Unimolecular Reactions of (Z)-(Z)-N-(λ5-phosphanylidene) Formohydrazonic Formic Anhydride: Intramolecular aza-Wittig Reaction in Competition with Mumm Rearrangement

2020 ◽  
Vol 17 (11) ◽  
pp. 884-889
Author(s):  
Somayeh Mirdoraghi ◽  
Hamed Douroudgari ◽  
Farideh Piri ◽  
Morteza Vahedpour
Keyword(s):  
Rate Constants ◽  
Density Functional ◽  
Wittig Reaction ◽  
Computational Study ◽  
Single Step ◽  
Low Energy ◽  
Coupled Cluster ◽  
Unimolecular Reaction ◽  
Single Step Reaction ◽  
Good Agreement

For (Z)-(Z)-N-(λ5-phosphanylidene) formohydrazonic formic anhydride, Aza-Wittig reaction and Mumm rearrangement are studied using both density functional and coupled cluster theories. For this purpose, two different products starting from one substrate are considered that are competing with each other. The obtained products, P1 and P2, are thermodynamically favorable. The product of the aza-Wittig reaction, P1, is more stable than the product of Mumm rearrangement (P2). For the mentioned products, just one reliable pathway is separately proposed based on unimolecular reaction. Therefore, the rate constants based on RRKM theory in 300-600 K temperature range are calculated. Results show that the P1 generation pathway is a suitable path due to low energy barriers than the path P2. The first path has three steps with three transition states, TS1, TS2, and TS3. The P2 production path is a single-step reaction. In CCSD level, the computed barrier energies are 14.55, 2.196, and 10.67 kcal/mol for Aza-Wittig reaction and 42.41 kcal/mol for Mumm rearrangement in comparison with the corresponding complexes or reactants. For final products, the results of the computational study are in a good agreement with experimental predictions.

Kinetics of esterification of monoisopropylphenols with phosphoryl trichloride

1989 ◽  
Vol 54 (5) ◽  
pp. 1311-1317
Author(s):  
Miroslav Magura ◽  
Ján Vojtko ◽  
Ján Ilavský
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Reaction Rates ◽  
Activation Energies ◽  
The Individual ◽  
Kinetics Of

The kinetics of liquid-phase isothermal esterification of POCl3 with 2-isopropylphenol and 4-isopropylphenol have been studied within the temperature intervals of 110 to 130 and 90 to 110 °C, respectively. The rate constants and activation energies of the individual steps of this three-step reaction have been calculated from the values measured. The reaction rates of the two isomers markedly differ: at 110 °C 4-isopropylphenol reacts faster by the factors of about 7 and 20 for k1 and k3, respectively. This finding can be utilized in preparation of mixed triaryl phosphates, since the alkylation mixture after reaction of phenol with propene contains an excess of 2-isopropylphenol over 4-isopropylphenol.

scholarly journals Separate Universe calibration of the dependence of halo bias on cosmic web anisotropy

2020 ◽  
Vol 499 (3) ◽  
pp. 4418-4431 ◽  
Author(s):  
Sujatha Ramakrishnan ◽  
Aseem Paranjape
Keyword(s):  
Dark Matter ◽  
High Precision ◽  
Gaussian Distribution ◽  
Initial Perturbation ◽  
Analytical Framework ◽  
Web Environment ◽  
Wide Range ◽  
Galaxy Assembly ◽  
Very High ◽  
Good Agreement

ABSTRACT We use the Separate Universe technique to calibrate the dependence of linear and quadratic halo bias b1 and b2 on the local cosmic web environment of dark matter haloes. We do this by measuring the response of halo abundances at fixed mass and cosmic web tidal anisotropy α to an infinite wavelength initial perturbation. We augment our measurements with an analytical framework developed in earlier work that exploits the near-lognormal shape of the distribution of α and results in very high precision calibrations. We present convenient fitting functions for the dependence of b1 and b2 on α over a wide range of halo mass for redshifts 0 ≤ z ≤ 1. Our calibration of b2(α) is the first demonstration to date of the dependence of non-linear bias on the local web environment. Motivated by previous results that showed that α is the primary indicator of halo assembly bias for a number of halo properties beyond halo mass, we then extend our analytical framework to accommodate the dependence of b1 and b2 on any such secondary property that has, or can be monotonically transformed to have, a Gaussian distribution. We demonstrate this technique for the specific case of halo concentration, finding good agreement with previous results. Our calibrations will be useful for a variety of halo model analyses focusing on galaxy assembly bias, as well as analytical forecasts of the potential for using α as a segregating variable in multitracer analyses.

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