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Monitoring the damage development by dynamic-mechanical and dielectric analyzer

Authors:
Sahbi Aloui at NETZSCH Group
Sahbi Aloui
Horst Deckmann at NETZSCH Group
Horst Deckmann
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Abstract

Static sealing elements undergo continuous changes in operating and environmental conditions. They are subject to natural, thermo-oxidative or mechanical aging processes and must be replaced after a certain time. The condition for cost efficiency is that a sealing gasket should be used over its entire service life without having to invest in complex and expensive monitoring systems. The simplest and smartest monitoring system is usually already present: the reinforcing filler, which can be electrically conductive.
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PR AX IS
P RACT ICE
14 KGK · 04 2019 www.kgk-rubberpoint.de
ZU SA MMENFASSUNG
Statisch beanspruchte Dichtun-
gen geben Auskunft über ihren
Verschleiß
Statische Dichtungselemente sind ständi-
gen Veränderungen der Betriebs- und Um-
weltbedingungen ausgesetzt. Sie unterlie-
gen verschiedenen Alterungsprozessen, die
ihre Abdichtungsleistung stark variieren
können und müssen daher nach einer ge-
wissen Zeit ausgetauscht werden. Kosten-
effizient ist es, eine statische Dichtung
über ihre gesamte Lebensdauer zu nutzen
ohne in komplexen und kostenintensiven
Überwachungssysteme investieren zu
müssen. Das einfachste und cleverste
Überwachungssystem ist meistens schon
vorhanden: der verstärkende Füllstoff, der
elektrisch leitfähig sein kann.
Sealing elements are used in tech-
nical applications to prevent mass
transfer between two components
or auxiliary chambers [1]. The desired
property profile is achieved primarily
through a variety of design options.
Besides the polymer and necessary ad-
ditives, the filler used also plays a cru-
cial role in establishing a sealing ele-
ment’s characteristics such as compres-
sive strength, thermal and chemical re-
sistance. Depending on the mounting
conditions for the different sealing sys-
tems, creep and relaxation processes
lead to premature mechanical aging
and premature wear of the seal. If iden-
tical sealing elements are used in differ-
ent applications, the aging processes in
the respective application can vary con-
siderably. Removing the seals and
checking their mechanical properties is
not a solution. As a rule, the seals can-
not be used after disassembly. Ideal in
this context would be a so-called „mark-
er“, which „reports“ the mechanical
state of the mounted seal and enables
continuous „monitoring“. Ideally, as
“marker” a combination of simultane-
ous dynamic mechanical and dielectric
analysis is used.
Static Seals provide information about
their own wear
Monitoring Damage Development by Dynamic-Mechanical and Dielectric Analyzer Static sealing ele-
ments undergo continuous changes in operating and environmental conditions. They are subject to natu-
ral, thermo-oxidative or mechanical aging processes and must be replaced after a certain time. The condi-
tion for cost efficiency is that a sealing gasket should be used over its entire service life without having to
invest in complex and expensive monitoring systems. The simplest and smartest monitoring system is
usually already present: the reinforcing filler, which can be electrically conductive.
Authors
Sahbi Aloui, Horst Deckmann
Netzsch Gerätebau, Ahlden
Sahbi.Aloui@Netzsch.com
Monitoring the damage development by
dynamic-mechanical and dielectric analyzer.
Bildquelle: alle Gabo Netzsch
... Since the dielectric response of elastomeric materials is governed by the current mechanical state of the filler network, changes in the filler network can be analyzed by simultaneous mechanical and dielectric measurements when the relationship between the mechanical state and the "snapshot" dielectric spectrum of the material is known [12][13][14][15]. In this case, the simultaneous analysis of the dynamic mechanical and dielectric properties delivers the current mechanical state of the built-in elastomeric materials [16]. ...
... The simultaneous dynamic-mechanical and dielectric measurements were performed with the dynamic-mechanical and dielectric analyzer DiPLEXOR® 500 N from NETZSCH Gerätebau GmbH equipped with a broadband dielectric spectrometer BDS 40 supplied by Novocontrol GmbH, shown in Fig. 5 [16,22]. ...
View
... Since the dielectric response of elastomeric materials is governed by the current mechanical state of the filler network, changes in the filler network can be analyzed by simultaneous mechanical and dielectric measurements when the relationship between the mechanical state and the "snapshot" dielectric spectrum of the material is known [12][13][14][15]. In this case, the simultaneous analysis of the dynamic mechanical and dielectric properties delivers the current mechanical state of the built-in elastomeric materials [16]. ...
... The simultaneous dynamic-mechanical and dielectric measurements were performed with the dynamic-mechanical and dielectric analyzer DiPLEXOR® 500 N from NETZSCH Gerätebau GmbH equipped with a broadband dielectric spectrometer BDS 40 supplied by Novocontrol GmbH, shown in Fig. 5 [16,22]. ...
Simultaneous characterization of dielectric and dynamic-mechanical properties of elastomeric materialsunder static and dynamic load
Article
  • Jan 2021
  • POLYMER
The inner dynamics of carbon black filled elastomeric material under static and dynamic load are examined by means of simultaneous dielectric and dynamic-mechanical analysis at room temperature. The experiments are performed on styrene butadiene rubber (SBR) samples filled with carbon black well above the dielectric percolation threshold. By increasing the mechanical load, a decrease in the conductivity is found due to continuous mechanical damage to the filler network structure, which prevents the transport of charge carriers through the sample via the carbon black network. The Cole-Cole equation is applied to fit the experimental data. The resulting fit-parameters show different load dependence. The mechanical damage to the filler network makes the relaxation processes broader and leads to higher relaxation times, whereby the relaxation strength increases. This has been attributed to an increase in the correlation length of the filler network with increasing load.
View
Influence of the Polarity of the Plasticizer on the Mechanical Stability of the Filler Network by Simultaneous Mechanical and Dielectric Analysis
Article
Full-text available
  • May 2022
Four styrene butadiene rubber (SBR) compounds were prepared to investigate the influence of the plasticizer polarity on the mechanical stability of the filler network using simultaneous mechanical and dielectric analysis. One compound was prepared without plasticizer and serves as a reference. The other three compounds were expanded with different plasticizers that have different polarities. Compared with an SBR sample without plasticizer, the conductivity of mechanically unloaded oil-extended SBR samples decreases by an order of magnitude. The polarity of the plasticizer shows hardly any influence because the plasticizers only affect the distribution of the filler clusters. Under static load, the dielectric properties seem to be oil-dependent. However, this behavior also results from the new distribution of the filler clusters caused by the mechanical damage and supported by the polarity grade of the plasticizer used. The Cole–Cole equation affirms these observations. The Cole–Cole relaxation time τ and thus, the position of maximal dielectric loss increases as the polarity of the plasticizer used is also increased. This, in turn, decreases the broadness parameter α implying a broader response function.
View
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