View source for In-situ Tensile Test in NMR

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<span style="font-size:1.2em;font-weight:bold;">In-situ tensile test in NMR</span>

Development of a hybrid testing method for coupling NMR spectroscopy and mechanical tensile testing for the investigation of elastomers

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==Objective==

The aim of the work presented here is to develop a [[Hybrid Methods|hybrid method]] for [[Polymer Diagnostic|polymer diagnostics]] that does not yet exist in this form [1−3]. In this hybrid method, conventional [[Tensile Test|tensile testing]] and, in future, [[Relaxation Plastics|stress relaxation testing]] under tensile stress are to be coupled with the [[Nuclear Magnetic Resonance Spectroscopy|nuclear magnetic resonance (NMR)]] method known from chemical analysis (see '''Fig. 1''') in order to establish a direct link to structural changes during the [[Deformation|deformation]] of an [[Elastomers|elastomer material]] [4−8]. This makes it possible to obtain stress–strain diagrams recorded in the [[Tensile Test|tensile test]] with information about the [[Strength|strength]] and deformation properties of the material being tested and, at the same time, to obtain information about the molecular structure and mobility of polymer chains using the nuclear magnetic resonance method [9–11] (see: [[Nuclear Magnetic Resonance Spectroscopy|nuclear magnetic resonance spectroscopy]]). The structural parameters for [[Polymer|polymeric]] materials obtained in this way are to serve as the basis for establishing structure-property relationships.


[[File:In-situ_Tensile_Test_Fig-1.jpg]]
{| 
|- valign="top"
|width="50px"|'''Fig. 1''': 
|width="600px" |Schematic presentation of the test setup for performing [[Tensile Test|tensile tests]] in an NMR device system
|}

==Development of the hybrid test method==

The innovative in-situ tensile testing device was constructed on the basis of a technological concept that involves the use of a pneumatic cylinder, as shown in '''Fig. 2'''. The corresponding designs and material specifications were based on the specifications of the superconducting NMR magnet, which has an 8 cm diameter room air drilling and a 3 cm diameter “sample chamber” in the NMR sample head. The pneumatic cylinder was placed in the upper part of the ambient air bore and is connected to the tensile or compression yoke by carbon fibre rods or, in the area of the NMR sample head, by glass rods. The tensile or compression yoke and all other mountings were manufactured from acrylonitrile butadiene styrene ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: ABS) using rapid prototyping technologies. The general choice of materials was based on their performance in strong magnetic fields so as not to interfere with the subsequent high-frequency excitation by the NMR method.


[[File:In-situ_Tensile_Test_Fig-2.jpg]]
{| 
|- valign="top"
|width="50px"|'''Fig. 2''': 
|width="600px" |Technological concept for the development of the innovative hybrid test equipment
|}

The necessary software was implemented in Microsoft's Visual Studio.NET development environment using the C# programming language. Various modules were implemented, including those for recording, displaying, and evaluating stress–strain diagrams. The functionality is based on commercially available software for evaluating [[Tensile Test|tensile tests]] (e.g., [https://www.zwickroell.com/ ZwickRoell GmbH & Co. KG, Ulm]]). This resulted in software components that provide a corresponding user interface for entering the test specimen geometry and important experiment parameters, as well as the option for evaluation. Furthermore, software components were implemented to control the in-situ tensile testing device and thus to send control signals and read out data signals from the sensors. These components enable the control of the pressure in the pneumatic cylinder, the measurement of the crosshead path and, indirectly, via prior calibration, the measurement of the force.

==Application==

'''Figure 3''' shows examples of the results obtained using the new [[Hybrid Methods|hybrid testing method]]. Separate core magnetic (determination of relaxation times ''T''<sub>2</sub> as structural parameters) and mechanical experiments were carried out on natural rubber vulcanizates (NR) with varying [[Cross-Linking Elastomers|cross-linking]] densities. Prismatic test specimens measuring 5 mm x 2 mm with a clamping length of 50 mm were used for the [[Tensile Test|tensile tests]], and test specimens measuring 5 mm x 5 mm x 2 mm were used for the [[Nuclear Magnetic Resonance Spectroscopy|nuclear magnetic investigations]]. The tensile test was used to determine the stress σ and strain ε, as well as relevant [[Material Value|characteristic values]]. A correlation was found between the structure-sensitive ''T''<sub>2</sub> relaxation times and the strain determined at the maximum force from the tensile test. The strain at maximum force εFmax and the ''T''<sub>2</sub> relaxation time decrease with increasing [[Degree of Cross-Linking Elastomers|cross-linking degree]] of the NR vulcanizates, which is due to the higher cross-linking and the associated greater restriction of chain mobility due to additional cross-linking points.

[[File:In-situ_Tensile_Test_Fig-3.jpg]]
{| 
|- valign="top"
|width="50px"|'''Fig. 3''': 
|width="600px" |Comparison of the relaxation time of free molecules and chain ends in the network with the strain at maximum force
|}

==Outlook==

The completion of the development of the novel [[Hybrid Methods|hybrid testing method]] requires further comparative investigations with reference systems. A further step will be the coupled investigation of stress relaxation processes (see: [[Relaxation Plastics|relaxation plastics]]) and thus the establishment of structure–property correlations. This new method is intended to make a significant contribution to the targeted improvement of application-relevant properties of [[Elastomers|elastomeric materials]]. In addition to the use of the hybrid method in the context of material development and optimization, the structural changes associated with [[Ageing|ageing processes]] are also to be directly detected by recording changes in relaxation times.

==See also==

* [[Nuclear Magnetic Resonance Spectroscopy|Nuclear magnetic resonance spectroscopy (NMR spectroscopy)]]
* [[Hybrid Methods|Hybrid methods]]
* [[Polymer Diagnostic|Polymer diagnostic]]
* [[Hybrid Methods, Examples|Hybrids methods, examples]]

==References==

{|
|-valign="top"
|[1]
|[[Bierögel, Christian|Bierögel, C.]]: Hybrid Methods of Polymer Diagnostics. In: [[Grellmann,_Wolfgang|Grellmann, W.]], [[Seidler,_Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser, Munich (2025) 4th Edition, pp. 487–499 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see [[AMK-Library]] under A 22) 
|-valign="top"
|[2]
|[https://www.researchgate.net/profile/Wolfgang-Grellmann Grellmann, W.], Langer, B.: Methods for Polymer Diagnostics for the Automotive Industry. Materialprüfung 55 (2013) 17–22 [https://www.polymerservice-merseburg.de/fileadmin/inhalte/psm/veroeffentlichungen/Methods_for_Polymer_Diagnostics_for_the_Automotive_Industry__Grellmann_Langer_2013_.pdf  Download as pdf]
|-valign="top"
|[3]
|[https://de.wikipedia.org/wiki/Wolfgang_Grellmann Grellmann, W.], Bierögel, C.: Laserextensometrie anwenden. Materialprüfung 40 (1998) 452–459; [https://doi.org/10.1515/mt-1998-4011-1206 https://doi.org/10.1515/mt-1998-4011-1206]
|-valign="top"
|[4]
|Döhler, S., Heuert, U., Grellmann, W.: Material Properties Imaging zur Werkstoffdiagnostik In: Forschungsbericht, Hochschule Merseburg (2011), S. 119–125 (ISBN 978-3-942703-07-9) 
|-valign="top"
|[5]
|Döhler, S., Heuert, U., Grellmann, W.: Material Properties Imaging zur Aufklärung von Materialeigenschaften, 13. Tagung Problemseminar „Deformation und Bruchverhalten von Kunststoffen“, Proceedings (2011), pp. 419–422 
|-valign="top"
|[6]
|Döhler, S., Glatz, D., Heuert, U., Grellmann, W.: Entwicklung einer neuartigen in-situ-Zugeinrichtung für kernmagnetische Untersuchungen an Elastomeren In: Honekamp, W., Schindler, P. (Eds.), 13. Nachwuchswissenschaftlerkonferenz Proceedings (2012), pp. 185–190 (ISBN 978-3-86870-436-5) 
|-valign="top"
|[7]
|Döhler, S., [[Reincke, Katrin|Reincke, K.]], Heuert, U., Grellmann, W.: Entwicklung eines hybriden Prüfverfahrens zur strukturellen Aufklärung von Deformationseigenschaften elastomerer Werkstoffe, 14. Problemseminar "Deformation und Bruchverhalten von Kunststoffen", 25.–27. Juni 2014, Merseburg, Proceedings pp. 657–663 (ISBN 978-3-942703-30-7) 
|-valign="top"
|[8]
|Döhler, S., Heuert, U., Reincke, K., Grellmann, W.: Entwicklung eines neuartigen hybriden Prüfverfahrens zur Kopplung von Zugversuch und strukturaufklärender NMR-Spektroskopie, Werkstoffprüfung 2015, Fortschritte in der Werkstoffprüfung für Forschung und Praxis, December 3 and 4, 2015, Bad Neuenahr, Proceedings pp. 267–272 (Eds.: Borsutzki, M., Moninger, G.) (ISBN 978-3-514-00816-8); see [[AMK-Library]] under M 36) 
|-valign="top"
|[9]
|Claridge, T. D. W.: High-Resolution NMR Techniques in Organic Chemistry Third Edition, Elsevier Science, Oxford (2016) (ISBN 978-0-0809-9986-9; E-Book ISBN 978-0-0809-9993-7) 
|-valign="top"
|[10]
|Friebolin, H.: Ein- und zweidimensionale NMR-Spektroskopie: Eine Einführung, 5th Edition Wiley-VCH Publishing (2013) (ISBN 978-3-527-33492-6) 
|-valign="top"
|[11]
|Blümich, B.: NMR Imaging of Materials, Clarendon Press, Oxford (2000) (ISBN 9780-1985-2676-6) 
|}

[[Category:Hybrid Methods]]
[[Category:Morphology and Micromechanics]]