A modelling approach for the heterogeneous oxidation of elastomers

Herzig, A.; Sekerakova, L.; Johlitz, Michael; Lion, Alexander

doi:10.1007/s00161-017-0568-8

Cited by 11 publications

(24 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The chemical ageing properties are then reflected by altered stress-strain properties of the rubber. The chemical ageing is frequently modelled by molecular dynamics [5] and internal inner variables that are determined by inner differential evolution equations [18][19][20][21]27,30], recently extended into their nonlinear counterpart [16]. In this paper, novel inner differential evolution equations are developed for the inner variables while containing fractional differential operators in order to allow for a wider spectrum of relaxation times found in real molecular networks, thus giving a richer structure to the model.…”

mentioning

confidence: 99%

Dynamic stiffness of chemically and physically ageing rubber vibration isolators in the audible frequency range

Kari

2017

Continuum Mech. Thermodyn.

View full text Add to dashboard Cite

The constitutive equations of chemically and physically ageing rubber in the audible frequency range are modelled as a function of ageing temperature, ageing time, actual temperature, time and frequency. The constitutive equations are derived by assuming nearly incompressible material with elastic spherical response and viscoelastic deviatoric response, using Mittag-Leffler relaxation function of fractional derivative type, the main advantage being the minimum material parameters needed to successfully fit experimental data over a broad frequency range. The material is furthermore assumed essentially entropic and thermo-mechanically simple while using a modified William-Landel-Ferry shift function to take into account temperature dependence and physical ageing, with fractional free volume evolution modelled by a nonlinear, fractional differential equation with relaxation time identical to that of the stress response and related to the fractional free volume by Doolittle equation. Physical ageing is a reversible ageing process, including trapping and freeing of polymer chain ends, polymer chain reorganizations and free volume changes. In contrast, chemical ageing is an irreversible process, mainly attributed to oxygen reaction with polymer network either damaging the network by scission or reformation of new polymer links. The chemical ageing is modelled by inner variables that are determined by inner fractional evolution equations. Finally, the model parameters are fitted to measurements results of natural rubber over a broad audible frequency range, and various parameter studies are performed including comparison with results obtained by ordinary, non-fractional ageing evolution differential equations.

show abstract

mentioning

confidence: 99%

Dynamic stiffness of chemically and physically ageing rubber vibration isolators in the audible frequency range

Kari

2017

Continuum Mech. Thermodyn.

View full text Add to dashboard Cite

show abstract

“…These DLO effects occur when the oxygen consumption by oxidation reactions in the specimen's surface is faster than the diffusion process. In addition, the new oxidative bonds close to the surface lead to deceleration or prohibit further oxygen diffusion, as well as the lower oxygen concentration in the polymer interior, which is more evident at higher temperatures 39,40 . For this reason, close values for hardness, CS and indentation modulus profile were obtained from the center of the specimens in these evaluated temperatures.…”

Section: Resultsmentioning

confidence: 81%

Service lifetime prediction of nitrile butadiene rubber gaskets used in plate heat exchangers

Zanzi

Souza

Dutra

et al. 2022

J of Applied Polymer Sci

View full text Add to dashboard Cite

Gasketed plate heat exchangers are characterized in a usual heat exchanger class. These systems employ elastomeric gaskets as the sealing element. Several conditions lead to oxidation and deterioration of these materials and their properties. In addition, the complex geometry of the gaskets and operation conditions may cause divergence in the expected aging behavior of the rubber. In light of this, this study aims to predict the service lifetime for nitrile butadiene rubber gaskets used in plate heat exchangers based on their geometry under thermo‐oxidative aging. These gaskets were evaluated by means of Shore A hardness, compression set (CS), and indentation modulus profile. Through aging‐sealing tests, an end‐of‐life criteria was determined concerning CS measurements and the service lifetime prediction was obtained by time–temperature superposition and WLF method. Diffusion‐limited oxidation effects were observed at high temperatures in postaging analysis and a non‐Arrhenius behavior was observed at 170°C. The value of 79% CS was obtained as end‐of‐life criteria from 60 to 140°C, ranged from 731 to 80 days, respectively, revealing an activation energy equivalent to 32.3 kJ mol−1. These results might support the maintenance planning control of gasketed plate heat exchangers.

show abstract

“…Thus, the process is called diffusion‐limited oxidation (DLO). [ 28 ] DLO effects can appear during aging depending on aging temperature, time, and oxygen permeability of the material. [ 25,29 ] In the case of EPDM samples, according to reports in the literature, the DLO effect appears only after 100 days at 150°C [ 3,25 ] ; that is, at higher temperatures and longer aging times than those applied in this study.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of the aging of elastomeric acrylonitrile‐butadiene rubber and ethylene‐propylene‐diene monomer gaskets used to seal plates heat exchanger

Souza

Zanzi

Paiva

et al. 2021

Polymer Engineering & Sci

View full text Add to dashboard Cite

Acrylonitrile‐butadiene rubber (NBR) and ethylene‐propylene‐diene monomer (EPDM) gaskets are used as seals in plates heat exchangers due to their elasticity and resilience. However, contact with fluids, oxygen, ozone, and heat lead to permanent deformation. This study investigates the degradation of gaskets submitted to similar service conditions: compressed in a groove for up to 360 h at 100 and 120°C. The analysis was carried through compression set (CS), compression stress relaxation, surface morphology, Shore A hardness, indentation modulus profile, crosslink density, and Fourier transform infrared region with attenuated total reflection analysis. For EPDM, in thermo‐oxidative aging there is a counterbalance between chain scission and crosslinking, which increases CS while hardness and crosslink density remain low. For NBR, diffusion‐limited oxidation causes heterogeneous oxidation, creating a crosslinking network near the surface. The values for CS, Shore A hardness, and crosslink density raised to 50%, 10%, and 75%, respectively. Furthermore, the side thermo‐oxidation was reduced due to the presence of the groove, which reduces oxygen access. Using FITR analysis, a thermo‐oxidative interaction mechanism was proposed for the EPDM and NBR gaskets. It was concluded that EPDM presented a more reliable behavior for the gasket and seal applications under the analyzed conditions.

show abstract

A modelling approach for the heterogeneous oxidation of elastomers

Cited by 11 publications

References 25 publications

Dynamic stiffness of chemically and physically ageing rubber vibration isolators in the audible frequency range

Dynamic stiffness of chemically and physically ageing rubber vibration isolators in the audible frequency range

Service lifetime prediction of nitrile butadiene rubber gaskets used in plate heat exchangers

Evaluation of the aging of elastomeric acrylonitrile‐butadiene rubber and ethylene‐propylene‐diene monomer gaskets used to seal plates heat exchanger

Contact Info

Product

Resources

About