Phenomenological Modeling of the Apparent Viscosity as a Function of the Degree of Curing of an EPDM Elastomer

MRS Advances ◽  
2020 ◽  
Vol 5 (62) ◽  
pp. 3205-3214
Author(s):  
S. Gómez-Jimenez. ◽  
A.M. Becerra-Ferreiro. ◽  
E. Jareño-Betancourt. ◽  
J. Vázquez-Penagos.
Keyword(s):  
Apparent Viscosity ◽  
Curing Kinetics ◽  
Transition Process ◽  
Practical Method ◽  
Phenomenological Approach ◽  
Gel Point ◽  
Viscosity Behavior ◽  
Regression Techniques ◽  
Degree Of Curing ◽  
Vulcanization Process

AbstractThe moving die rheometer technique (MDR) is used to measure the elastic and viscous components of rubber. The analysis of the rheometry and the kinetic behavior can be used to obtain mathematical models to predict the viscosity of elastomers as a function of the temperature, the time and the degree of curing. These predictions allow the control, the optimization and the design of the process. In this research the phenomenological model of Kamal-Sourour was used to describe the curing kinetics, while the Carreau Macosko model was used to describe the viscous behavior of an ethylene - propylene diene industrial type compound (EPDM). The mathematical parameters for each model where determined by using non-linear regression techniques. Since the viscosity increases significantly while the curing rate decreases, we proposed a mathematical model based on the Carreau expression in order to consider the influence of the kinetic of curing in the apparent viscosity behavior. It was found that after the curing rate reaches its maximum the viscosity tends to infinity; that is, the chemical transition process known as fluidity point or gel point occurs in the vicinity of maximum curing rate. According to the results, it is concluded that rubber viscosity is well described by considering the curing variations; the fluidity point in the vulcanization process can also be obtained by the practical method of phenomenological approach.

Experimental Research on Apparent Viscosity Behavior of Cationic/Anionic Worm-Like Micelles

2014 ◽  
Vol 644-650 ◽  
pp. 4884-4887
Author(s):  
Ni Li ◽  
Rui Zhang
Keyword(s):  
Double Bond ◽  
Cationic Surfactant ◽  
Experimental Research ◽  
Anionic Surfactant ◽  
Apparent Viscosity ◽  
Self Assembly ◽  
Molar Ratio ◽  
Trimethylammonium Chloride ◽  
Viscosity Behavior

In this paper, cationic surfactant and anionic surfactant form worm-like micelles by self-assembly. The cationic surfactant is acryloxyethyl trimethylammonium chloride (DAC). The anionic surfactant is potassium erucic (KEU). Mixed the cationic surfactant and anionic surfactant, because the DAC molecule contain a double bond, then, polymerized the solution with VA - 044. By contrast many experiments, the purpose is to get the highest apparent viscosity. After comparing, when the molar ratio of n (KEU) : n (DAC) = 5:1, the largest viscosity of worm-like micelles is 1450mPa•s.

Investigating Curing Kinetics for a Thin-Walled Carbon Fibre Structure

2020 ◽  
pp. 58-70
Author(s):  
Ya. Chen ◽  
P.P. Maung ◽  
G.V. Malysheva
Keyword(s):  
Carbon Fibre ◽  
Exothermic Reaction ◽  
Curing Kinetics ◽  
Temperature Gradients ◽  
Computational Method ◽  
Temperature Fields ◽  
Filament Wound ◽  
Initial Stage ◽  
Aerial Vehicle ◽  
Degree Of Curing

The paper presents a computational method and an example of using it to derive parameters of a high-pressure filament-wound carbon fibre vessel designed for unmanned aerial vehicle applications. A feature of the vessel design is its variable thickness, which may result in temperature gradients, residual stresses, and diminished strength. We propose a method for assessing curing kinetics that takes into account the heat emitted during this process. We used the ESI PAM-RTM software package for simulation and determined that at the initial stage of the curing process the temperature and degree of curing in the thinner part of the product exceed those in its thicker part. As the degree of curing increases, the exothermic reaction taking place affects the temperature fields, which leads to an increase in temperatures and degree of curing in the thicker regions. In order to level the temperature gradients and degree of curing over the whole vessel, we propose to heat it at different rates. Our investigation results allowed us to establish the optimum manufacturing conditions ensuring the minimum temperature gradient values

scholarly journals UV cured platinum-free, soft PDMS networks

2014 ◽  
Author(s):  
Anders Egede Daugaard ◽  
Kaustav Goswami ◽  
Anne Ladegaard Skov
Keyword(s):  
Mechanical Properties ◽  
Ambient Temperature ◽  
Polymer Matrix ◽  
Dielectric Spectroscopy ◽  
Curing Kinetics ◽  
Gel Point ◽  
Materials Properties ◽  
Dimethyl Siloxane ◽  
Photochemical Crosslinking ◽  
Curing Method

In recent years, UV chemistry has gained importance in curing of elastomers as it allows for rapid reactions at ambient temperature and thereby saves energy in processing. Current techniques often apply platinum in the UV-cured systems, which is challenged by the increasing cost of platinum. A novel platinum free photochemical curing method for soft poly (dimethyl siloxane) (PDMS) networks based on commercially available starting materials was developed. Soft PDMS networks were obtained through photochemical thiol-ene crosslinking of α,ω-vinyl terminated PDMS with a hexa-functional thiol PDMS. Investigations showed that direct photochemical crosslinking led to slow curing kinetics and resulted in a soft PDMS with inferior materials properties. The efficiency of the crosslinking chemistry was substantially improved, through development of a two-step curing reaction. Initially, the crosslinker and excess linear α,ω-vinyl-PDMS were reacted below the gel-point under UV irraditation into hyperbranched structures. The hyperbranched structures were found to be fast and efficiently crosslinked into ideal networks with good mechanical properties. Finally the approach also allows for localization of fillers in the polymer matrix. The properties of the prepared networks were investigated by both rheology and dielectric spectroscopy.

Research on Apparent Viscosity Behavior of Municipal Sludge

2014 ◽  
Vol 496-500 ◽  
pp. 2984-2988 ◽  
Author(s):  
Song Hui Zhao ◽  
Bo Lou ◽  
Wei Qian ◽  
Xin Feng Long
Keyword(s):  
Moisture Content ◽  
Negative Correlation ◽  
Apparent Viscosity ◽  
Municipal Sludge ◽  
Viscosity Behavior

Researches about the viscous of municipal sludge can be constructive especially in its drying and transportation. The change of apparent viscosity in terms of moisture content and temperature reveals that the former is primary. The apparent viscosity increases rapidly at moisture content lower than 88% with an exponent function and It is negative correlation with moisture content above 90% but only a litter change which has nothing to do with the temperature. However, it becomes to oscillate below 87% of moisture content which is attributed to complicated activities of microbe and temperature.

scholarly journals Kinetic Study of the Epoxy System BADGE n = 0/IPD/ABS

Proceedings ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 61 ◽  
Author(s):  
Francisco Fraga-López ◽  
Eugenio Rodríguez-Núñez ◽  
José Manuel Martínez-Ageitos ◽  
Lucia López Arias ◽  
Uxío Valcárcel-Rubinos
Keyword(s):  
Entire Range ◽  
Reaction Rate ◽  
Acrylonitrile Butadiene Styrene ◽  
Curing Kinetics ◽  
Diglycidyl Ether ◽  
Epoxy System ◽  
Degree Of Curing ◽  
The Impact ◽  
Kinetics Of ◽  
Butadiene Styrene

In this study, we investigated the curing kinetics of the epoxy system formed by the epoxy resin Diglycidyl ether of bisphenol A, Isophorone diamine hardener (IPD), and the thermoplastic modification agent Acrylonitrile butadiene styrene or ABS. The introduction of a third component, in this case ABS, has been carried out to improve the application of this system in waterproofing and use of paints, as well as improving resistance to the impact of this type of systems. In addition, obtaining kinetic and respective parameters will allow us to identify the properties and gain knowledge of possible applications in the industry. In particular, it is intended to reach a kinetic equation that is capable of describing variation in the reaction rate according to the degree of curing for the entire range of conversions, starting from the model proposed by Kamal et al.

Rheological behaviors of anaerobic granular sludge in a spiral symmetry stream anaerobic bioreactor

2015 ◽  
Vol 72 (4) ◽  
pp. 658-664 ◽  
Author(s):  
Xiaoguang Chen ◽  
Ruobin Dai ◽  
Xinyi Xiang ◽  
Chengyu Ma ◽  
Gang Li ◽  
...  
Keyword(s):  
Apparent Viscosity ◽  
Granular Sludge ◽  
Shear Thinning ◽  
Anaerobic Granular Sludge ◽  
Anaerobic Bioreactor ◽  
Rheological Behaviors ◽  
Viscosity Behavior ◽  
Thixotropic Behavior ◽  
The Relationship ◽  
Sludge Concentration

The rheological behaviors of the anaerobic granular sludge (AGS) in a spiral symmetry stream anaerobic bioreactor (SSSAB) were investigated. Shear-thinning behavior, thixotropic behavior, concentration–viscosity behavior and temperature–viscosity behavior were evaluated based on the constitutive equation of the AGS. The results indicated that the Herschel–Bulkley model was able to adequately describe the constitutive relation of AGS in the SSSAB. The AGS also showed shear-thinning behavior as well as thixotropic behavior. The critical shear rate and network strength of the AGS were 61.8 s−1 and 497.0 W m−3, respectively. The relationship between the apparent viscosity and the sludge concentration was illustrated and explained by the Woodcock formula. The relationship between apparent viscosity of the AGS and temperature could be modeled using the Arrhenius equation. The AGS was significantly thermo-sensitive and its mean energy of activation was 14.640 kJ mol−1. Notably, it was necessary to consider such behaviors in the hydrodynamic modeling of SSSAB in which shear condition, sludge concentration and temperature were in non-uniform distribution.

scholarly journals Self Regulation Santri Penghafal Alquran Usia Sekolah Dasar

2020 ◽  
Vol 3 (2) ◽  
pp. 135-146
Author(s):  
Kharis Sulaiman Hasri ◽  
Suyadi Suyadi
Keyword(s):  
Elementary School ◽  
Qualitative Method ◽  
Extrinsic Motivation ◽  
Self Regulation ◽  
Transition Process ◽  
Phenomenological Approach ◽  
School Students ◽  
Elementary School Age ◽  
Data Collection Instrument ◽  
Depth Interviews

The purpose of this study is to explore self-regulation of Alquran memorizers in elementary school age. This study used a qualitative method with a phenomenological approach. The participants were collected using purposive sampling, which consisted of six students, five parents, and one teacher. The data collection instrument used semi-structured in-depth interviews and observation guidelines. The data were analyzed using the theory of Miles and Huberman with the stages of reduction, presentation, and conclusion. The self-regulation of elementary school students who memorize the Alquran is still guided by their parents both in setting goals, motivation and aspects of affection. In achieving goals, it is also influenced by the motivational aspects which are dominated by transcendental motivation. Meanwhile, the affection aspect occurs in a transition process from extrinsic motivation to intrinsic motivation.

The role of differential phase contrast in electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 176-177
Author(s):  
E.M. Waddell ◽  
J.N. Chapman ◽  
R.P. Ferrier
Keyword(s):  
Phase Contrast ◽  
Practical Method ◽  
Position Vector ◽  
Differential Phase ◽  
Pure Phase ◽  
Differential Phase Contrast ◽  
The Difference ◽  
Image Position ◽  
First Moment

Dekkers and de Lang (1977) have discussed a practical method of realising differential phase contrast in a STEM. The method involves taking the difference signal from two semi-circular detectors placed symmetrically about the optic axis and subtending the same angle (2α) at the specimen as that of the cone of illumination. Such a system, or an obvious generalisation of it, namely a quadrant detector, has the characteristic of responding to the gradient of the phase of the specimen transmittance. In this paper we shall compare the performance of this type of system with that of a first moment detector (Waddell et al.1977).For a first moment detector the response function R(k) is of the form R(k) = ck where c is a constant, k is a position vector in the detector plane and the vector nature of R(k)indicates that two signals are produced. This type of system would produce an image signal given bywhere the specimen transmittance is given by a (r) exp (iϕ (r), r is a position vector in object space, ro the position of the probe, ⊛ represents a convolution integral and it has been assumed that we have a coherent probe, with a complex disturbance of the form b(r-ro) exp (iζ (r-ro)). Thus the image signal for a pure phase object imaged in a STEM using a first moment detector is b2 ⊛ ▽ø. Note that this puts no restrictions on the magnitude of the variation of the phase function, but does assume an infinite detector.

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