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Article

Rheological Study of Gelation and Crosslinking in Chemical Modified Polyamide 12 Using a Multiwave Technique

1
Department of Polymer Engineering, University of Bayreuth, Universitätsstrasse 30, 95447 Bayreuth, Germany
2
Bavarian Polymer Institute, Universitätsstrasse 30, 95447 Bayreuth, Germany
*
Author to whom correspondence should be addressed.
Polymers 2020, 12(4), 855; https://doi.org/10.3390/polym12040855
Received: 17 February 2020 / Revised: 2 April 2020 / Accepted: 3 April 2020 / Published: 7 April 2020
(This article belongs to the Special Issue Polymer Rheology: Fundamentals and Applications)
When processing particular polymers, it may be necessary to increase the molecular weight, for example, during polymer recycling or foaming. Chemical additives such as chain extenders (CE) are often used to build up the molecular weight during reactive extrusion. One issue of chain extenders, however, is that they can cause gelation or crosslinking of the polymer during processes with long residence times. This can lead to strong process fluctuations, undesired process shutdowns due to uncontrollable torque and pressure fluctuations and finally consistent material quality cannot be guaranteed. To measure and understand the reactivity between the polymer and the CE a rheological test can help. However, the standard gel point evaluation used for thermosets by examining the point of intersection of storage- and loss modules is not suitable, as this method is frequency-dependent. This study uses a multiwave rheology test to identify the gel-point more reliably. Both evaluation methods were compared on a polyamide 12 system, which is modified with an industrially relevant chain extender. The results show that the multiwave test can be applied on a chemical modified thermoplastic system and that the material system indicates a general tendency to crosslink. The frequency-independent gel-point evaluation shows that the gel-point itself is dependent on the processing temperature. Finally, it was possible to detect undesired side reactions, which are not recognizable with the standard testing method. Both findings are directly relevant for the reactive extrusion process and help to understand the mechanism of gelation. View Full-Text
Keywords: rheology; multiwave; gelation; crosslinking; polyamide; PA12; chemical modification; chain extender; Joncryl; Vestamid rheology; multiwave; gelation; crosslinking; polyamide; PA12; chemical modification; chain extender; Joncryl; Vestamid
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MDPI and ACS Style

Dörr, D.; Kuhn, U.; Altstädt, V. Rheological Study of Gelation and Crosslinking in Chemical Modified Polyamide 12 Using a Multiwave Technique. Polymers 2020, 12, 855. https://doi.org/10.3390/polym12040855

AMA Style

Dörr D, Kuhn U, Altstädt V. Rheological Study of Gelation and Crosslinking in Chemical Modified Polyamide 12 Using a Multiwave Technique. Polymers. 2020; 12(4):855. https://doi.org/10.3390/polym12040855

Chicago/Turabian Style

Dörr, Dominik, Ute Kuhn, and Volker Altstädt. 2020. "Rheological Study of Gelation and Crosslinking in Chemical Modified Polyamide 12 Using a Multiwave Technique" Polymers 12, no. 4: 855. https://doi.org/10.3390/polym12040855

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