scholarly journals CHEMO-MECHANICAL MODEL FOR PREDICTING THE LIFETIME OF EPDM RUBBERS

2019 ◽  
Vol 92 (4) ◽  
pp. 722-748 ◽  
Author(s):  
Xavier Colin ◽  
Mouna Ben Hassine ◽  
Moussa Nait-Abelaziz
Keyword(s):  
Mechanical Behavior ◽  
Thermal Aging ◽  
Mechanical Model ◽  
Degradation Kinetics ◽  
Weight Changes ◽  
Cross Link ◽  
Elementary Reactions ◽  
Industrial Material ◽  
Macromolecular Network ◽  
Concentration Changes

ABSTRACT A chemo-mechanical model has been developed for predicting the long-term mechanical behavior of EPDM rubbers in a harsh thermal oxidative environment. Schematically, this model is composed of two complementary levels: The “chemical level” calculates the degradation kinetics of the macromolecular network that is introduced into the “mechanical level” to deduce the corresponding mechanical behavior in tension. The “chemical level” is derived from a realistic mechanistic scheme composed of 19 elementary reactions describing the thermal oxidation of EPDM chains, their stabilization against oxidation by commercial antioxidants but also by sulfide bridges, and the maturation and reversion of the macromolecular network. The different rate constants and chemical yields have been determined from a heavy thermal aging campaign in air between 70 and 170 °C on four distinct EPDM formulations: additive free gum, unstabilized and stabilized sulfur vulcanized gum, and industrial material. This “chemical level” has been used as an inverse resolution method for simulating accurately the consequences of thermal aging at the molecular (concentration changes in antioxidants, carbonyl products, double bonds, and sulfide bridges), macromolecular (concentration changes in chain scissions and cross-link nodes), and macroscopic scales (weight changes). Finally, it gives access to the concentration changes in elastically active chains from which are deduced the corresponding changes in average molar mass MC between two consecutive cross-link nodes. The “mechanical level” is derived from a modified version of the statistical theory of rubber elasticity, called the phantom network theory. It relates the elastic and fracture properties to MC if considering the macromolecular network perfect, and gives access to the lifetime of the EPDM rubber based on a relevant structural or mechanical end-of-life criterion. A few examples of simulations are given to demonstrate the reliability of the chemo-mechanical model.

Mechanical behavior of poly(methyl methacrylate)-based ionogels

Soft Matter ◽  
2014 ◽  
Vol 10 (40) ◽  
pp. 7993-8000 ◽  
Author(s):  
Mingyu Li ◽  
Jianyu Li ◽  
Hui Na ◽  
Joost J. Vlassak
Keyword(s):  
Methyl Methacrylate ◽  
Mechanical Behavior ◽  
Fracture Energy ◽  
Cross Link ◽  
Poly Methyl Methacrylate ◽  
Link Density ◽  
Cross Link Density ◽  
The Cross ◽  
The Ideal

We demonstrate that the fracture energy of ionogels correlates inversely with the cross-link density. The behavior of ionogels is well captured by the ideal elastomeric gel model.

Coupled analysis on hyper-viscoelastic mechanical behavior and macromolecular network alteration of rubber during thermo-oxidative aging process

Polymer ◽  
2019 ◽  
Vol 171 ◽  
pp. 15-24 ◽  
Author(s):  
Jieying Zhi ◽  
Qinglin Wang ◽  
Mengjie Zhang ◽  
Zhenze Zhou ◽  
Anna Liu ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Aging Process ◽  
Coupled Analysis ◽  
Oxidative Aging ◽  
Macromolecular Network

Effects of thermal aging on thermo-mechanical behavior of a glass sealant for solid oxide cell applications

2014 ◽  
Vol 34 (10) ◽  
pp. 2525-2534 ◽  
Author(s):  
Hamid Abdoli ◽  
Parvin Alizadeh ◽  
Dino Boccaccini ◽  
Karsten Agersted
Keyword(s):  
Mechanical Behavior ◽  
Thermal Aging ◽  
Solid Oxide ◽  
Solid Oxide Cell

A mechanical model for adjustable passive stiffness in rabbit detrusor

2006 ◽  
Vol 101 (4) ◽  
pp. 1189-1198 ◽  
Author(s):  
John E. Speich ◽  
Kevin Quintero ◽  
Christopher Dosier ◽  
Lindsey Borgsmiller ◽  
Harry P. Koo ◽  
...  
Keyword(s):  
Steady State ◽  
Mechanical Model ◽  
Strain Softening ◽  
Slow Component ◽  
Viscoelastic Model ◽  
Passive Force ◽  
Passive Stiffness ◽  
Cross Link ◽  
Force Relaxation ◽  
Adjustable Passive Stiffness

Strips of rabbit detrusor smooth muscle (DSM) exhibit adjustable passive stiffness characterized by strain softening: a loss of stiffness on stretch to a new length distinct from viscoelastic behavior. At the molecular level, strain softening appears to be caused by cross-link breakage and is essentially irreversible when DSM is maintained under passive conditions (i.e., when cross bridges are not cycling to produce active force). However, on DSM activation, strain softening is reversible and likely due to cross-link reformation. Thus DSM displays adjustable passive stiffness that is dependent on the history of both muscle strain and activation. The present study provides empirical data showing that, in DSM, 1) passive isometric force relaxation includes a very slow component requiring hours to approach steady state, 2) the level of passive force maintained at steady state is less if the tissue has previously been strain softened, and 3) tissues subjected to a quick-release protocol exhibit a biphasic response consisting of passive force redevelopment followed by force relaxation. To explain these and previously identified characteristics, a mechanical model for adjustable passive stiffness is proposed based on the addition of a novel cross-linking element to a hybrid Kelvin/Voigt viscoelastic model.

Tailoring single chain polymer nanoparticle thermo-mechanical behavior by cross-link density

Soft Matter ◽  
2017 ◽  
Vol 13 (15) ◽  
pp. 2808-2816 ◽  
Author(s):  
Suwon Bae ◽  
Or Galant ◽  
Charles E. Diesendruck ◽  
Meredith N. Silberstein
Keyword(s):  
Mechanical Behavior ◽  
Single Chain ◽  
Cross Link ◽  
Chain Polymer ◽  
Polymer Nanoparticle ◽  
Link Density ◽  
Cross Link Density

Effects of acrylonitrile content on thermal characteristics and thermal aging properties of carbon black-filled NBR composite

2020 ◽  
pp. 009524432094124
Author(s):  
Young Seok Lee ◽  
KiRyong Ha
Keyword(s):  
Thermal Aging ◽  
Aging Process ◽  
Elastic Recovery ◽  
Thermal Characteristics ◽  
Butadiene Rubber ◽  
Cross Link ◽  
Scanning Calorimetry ◽  
Aging Properties ◽  
Link Density ◽  
Cross Link Density

In seal applications, thermal characteristics and thermal aging properties of rubber are essential factors in determining the applicable temperature range and lifetime of the seal. In this study, thermal characteristics and thermal aging properties of the acrylonitrile butadiene rubber composite in response to the acrylonitrile (ACN) content were investigated. Thermal stability, glass transition temperature ( T g), and dynamic property were determined by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis, respectively. The results showed that T g, thermal decomposition temperature, and tan δ were increased as the ACN content increased. To investigate the thermal aging properties of the composite, the composite was subjected to an accelerated thermal-oxidative and thermal aging process at 100°C for 168 h. The aged composites were evaluated by investigating the change in cross-link density, mechanical properties, and elastic recovery. The change in the chemical functional group was also studied using attenuated total reflectance Fourier transform infrared spectroscopy. The results indicate that subjecting the composite to thermal-oxidative and thermal aging process decreased the elongation at break and elastic recovery, while the cross-link density, Shore A hardness, and 100% modulus were increased. All of the properties were also dependent on the ACN content as well as the aging conditions.

scholarly journals Elasto – plastic modelling of the behaviour of non - active clays under chemo – mechanical actions

2020 ◽  
Vol 205 ◽  
pp. 04011
Author(s):  
Guido Musso ◽  
Giulia Scelsi ◽  
Gabriele Della Vecchia
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Mineralogical Composition ◽  
Pore Fluid ◽  
Fluid Composition ◽  
Highly Active ◽  
Modified Cam Clay ◽  
Concentration Changes ◽  
Slope Instabilities ◽  
Soil Activity

Environmental variables such as temperature, matric suction and pore fluid composition are well known to influence the hydro-mechanical behavior of clays and shales. The type and the relevance of this influence depends on the mineralogical composition and on the fabric of the material. Soil activity is an engineering proxy for mineralogical composition which can be used for a preliminary characterization of the expected type of behaviour under chemical actions, if those do not imply very significant cation exchange or pH variations. Very large chemo-mechanical effects occur in highly active soils used in engineering works such as barriers for nuclear waste or landfills, however concentration changes also impact on the mechanical behavior of non – active soils and rocks, such as illitic or natural blends of clays. Such materials are widely distributed in nature and their mechanical response upon chemical changes can be problematic in many cases. Examples of engineering relevance include vast slope instabilities promoted by fabric changes due to desalinization in Scandinavian quick clays, and instability or convergence issues for boreholes drilled in shales exposed to muds with a different chemical composition from the one of the pore fluid. An elastoplastic model is formulated to simulate the volumetric behaviour of such materials along chemical and mechanical loads. In addition to the parameters of the Modified Cam Clay, it requires defining the dependency of the elasto-plastic compliance and reference void ratio on pore fluid salinity. The model performs well against experiments from literature where complex chemo-mechanical histories were imposed.

Effect of Die Chip-Outs and Reflow Temperature on the Mechanical Behavior of a 5-Die-Stacked Chip Scale Package

2007 ◽  
Author(s):  
Dennis Evan ◽  
L. Balacano ◽  
Lito P. De La Rama
Keyword(s):  
Stress Concentration ◽  
Mechanical Behavior ◽  
Failure Mechanism ◽  
Mechanical Model ◽  
Fracture Analysis ◽  
Active Area ◽  
Corner Crack ◽  
Reflow Temperature ◽  
Chip Scale Package ◽  
Corrective Actions

Abstract During package qualification, a 5-die-stacked chip scale package was being marginally triggered on high stand-by current collectively known as Power ICCS failure. Affected lots are subjected to 3x reflow at 240°C. Post reflow failures include blown_up, high standby current in Vcc pin (ISBLO), and high standby current in Vccq pin (ISBLOQ). Backside chip-outs are observed on Die 1 and Die 3 of the three failures. Electrical validation showed that only Die 3 is failing. Corner crack on Die 3 is common to the blown_up and ISBLO failing units while crack on Die 3 backside is observed to propagate toward the active area on ISBLOQ failing units. Fracture analysis results show that the crack of the three failures all originated from die backside chip-out. Thermo-mechanical model of the package shows that, by design, Die 3 generates the highest stress concentration. Results show that if chip-outs are present on the area of the die with the highest stress concentration and the unit is subjected to reflow temperature of 240°C, die crack will propagate from the chip-out. This paper presents the unique failure mechanism observed on a 5-die-stacked chip scale package and the corrective actions applied to solve the issue.

Kinetics of SiO2 Nanofibres Dissolution in the Simulated Lung Environment

2008 ◽  
Vol 39-40 ◽  
pp. 347-350 ◽  
Author(s):  
Lukáš Brázda ◽  
Jarmila Studničková ◽  
Petr Exnar ◽  
Aleš Helebrant
Keyword(s):  
Dissolution Rate ◽  
Weight Changes ◽  
Factors Affecting ◽  
Lung Fluid ◽  
Corrosive Solution ◽  
Concentration Changes ◽  
Tissue Geometry ◽  
Rate Limit ◽  
Risk Of Cancer ◽  
Kinetics Of

To avoid the risk of cancer or respiratory diseases, nanofibres have to biodegrade in lung fluid when inhaled. There are two main factors affecting behaviour of the nanofibres in living tissue – geometry of fibres and biopersistence. A dissolution rate of SiO2 nanofibres in a simulated lung environment was tested in this work. Distilled water buffered with TRIS and HCl to pH 7.6 was used as a simple simulated extracellular lung fluid (SLF). Fibres were tested both under the static and dynamic conditions of the corrosive solution. Dissolution rates were calculated from both SiO2 concentration changes in solutions and weight changes of fibres during the exposition. The dissolution rate of tested SiO2 nanofibres was at the rate limit, where fibres could be considered as harmless for health.

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