View source for Durability Elastomers

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<span style="font-size:1.2em;font-weight:bold;">Durability elastomers</span>
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==General==

In a durability test, one or more [[Material & Werkstoff|materials]] are exposed to practice-oriented conditions over a defined period of time. These conditions of artificial [[Ageing|ageing]] can be very diverse and range from thermo-oxidative, thermal and thermal-medial stress to artificial weathering and a combination of these stresses with mechanical [[Stress|stress]] and/or alternating stress between the different types of stress. The reaction of the [[Material & Werkstoff|material]](s) to the selected, realistic stress is to be recorded quantitatively in order to evaluate its durability. For this reason, [[Specimen|test specimens]] or [[Test Piece|test pieces]] are usually taken at different times and tests are carried out. For [[Polymer|polymer]] [[Material & Werkstoff|materials]] in general, a selection of direct and indirect methods is available for this purpose [1].

==Indirect verification of durability==

Indirect evidence of age-related material changes is usually provided by mechanical testing. The literature on [[Elastomers|elastomers]] very often describes the use of [[Tensile Test|tensile tests]] and/or [[Hardness|hardness tests]] to quantitatively measure ageing effects and thus indirectly prove ageing. Less frequently, for example, [[Tear Test|tear tests]], investigations using [[Elastic Modulus#Dynamic-mechanical analysis (DMA)|dynamic mechanical analysis (DMA)]], special [[Testing|tests]] such as stress [[Relaxation Plastics|relaxation]] investigations or [[Compression Test|measurements of compression]] set are carried out. The use of [[Fracture Mechanical Testing|fracture mechanics investigations]] should also be considered in the context of durability investigations due to their high structural sensitivity [2].

The evaluation of the characteristics of a [[Surface|surface]], such as roughness or specific [[Surface Tension and Interfacial Tension|surface tension]], in a before/after comparison can also be helpful in assessing durability and elucidating [[Ageing Elastomers|ageing]] mechanisms.

==Direct verification methods for durability==

Direct methods such as [[FTIR Spectroscopy|infrared spectroscopy]] (IR spectroscopy), [[Nuclear Magnetic Resonance Spectroscopy|nuclear magnetic resonance]] (NMR spectroscopy), X-ray photoelectron spectroscopy (XPS), [[Differential Scanning Calorimetry (DSC)|differential scanning calorimetry (DSC)]], chemiluminescence, gel permeation chromatography (GPC) and Raman spectroscopy can be used to directly detect age-related changes such as (post-)[[Cross-linking Elastomers|cross-linking]], chain scission, and the formation and degradation of functional groups.

In studies on the durability of [[Elastomers|elastomeric materials]], IR spectroscopy is used to detect structural changes, e.g. in the form of age-related oxidation of chain segments with the formation of carbonyl or hydroxyl groups, for example, whereby limitations in applicability due to carbon black reinforcement often have to be accepted. A combination of [[Thermogravimetric Analysis (TGA)|thermogravimetric analysis (TGA)]] and [[FTIR Spectroscopy|FTIR spectroscopy]], for which commercial devices are available, also allows temperature-resolved evaluation of decomposition and degradation processes. Investigations into swelling behaviour can also contribute to clarifying the change in [[Degree of Cross-Linking Elastomers|cross-linking density]] due to ageing. [[Nuclear Magnetic Resonance Spectroscopy||NMR spectroscopy]] can also be used to obtain information about the polymer network, i.e. ageing-related changes can be detected via the relaxation times to be determined.

Many studies documented in the literature on the [[Ageing Elastomers|ageing behaviour of elastomeric materials]] often deal only with either direct or indirect methods. The results have shown that a combination of the results of various direct and indirect methods and test procedures provides the most meaningful results in terms of elucidating age-related structural changes (see also: [[Hybrid Methods, Examples|hybrid methods, examples]]).

==See also==

* [[Ageing]]
* [[Ageing Elastomers|Ageing elastomers]]
* [[Cross-linking Elastomers|Cross-linking elastomers]]
* [[Degree of Cross-Linking Elastomers|Degree of cross-linking elastomers]]
* [[Hybrid Methods, Examples|Hybrid methods, Examples]]

==References==

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|[1]
|[[Ehrenstein, Gottfried W.|Ehrenstein, G. W.]], Pongratz, S.: Beständigkeit von Kunststoffen, Carl Hanser, Munich Vienna (2007), ISBN 978-3-446-21851-2; see AMK-Library under G 31) 
|-valign="top"
|[2]
|[[Reincke,_Katrin|Reincke, K.]], Langer, B., [[Grellmann,_Wolfgang|Grellmann, W.]], Döhler. S., Heuert, U.: Alterung und Beständigkeitsuntersuchungen von Elastomerwerkstoffen. KGK Kautschuk Gummi Kunststoffe 67 (2014) 10, pp. 60–67 DOI: https://www.kgk-rubberpoint.de/wp-content/uploads/migrated/paid_content/artikel/3324.pdf 
|}

[[Category:Elastomers]]
[[Category:Ageing]]