Determination of the Topology Freezing Transition Temperature (Tv) of Vitrimers

Vitrimers are covalently crosslinked polymers with adaptable network structure providing a unique property profile. This study shows a newly-developed method for the direct determination of the topology freezing transition temperature by creep measurements.

Introduction

Vitrimers are covalently crosslinked materials with adaptable network structure by associative bond exchange reactions[1]. For thermally-triggered vitrimers this unique functionality provides stable material properties governed by the covalent network below the topology freezing transition (Tv). Importantly, above Tv, where bond exchange reactions become significantly fast, the material turns into a plastified state useable for various application relevant deformation, shaping and joining procedures. This means vitrimers are potentially reprocessable, recyclable, self-healable and weldable although they are covalently crosslinked[1-3]. As a matter of fact, the service temperature range of thermo-activated vitrimers is primarily determined by Tv.

In the present study, the basic procedure of a newlydeveloped method for the reliable determination of Tv is presented for an epoxy-acid vitrimer undergoing thermo-activated transesterification exchange reactions[4]. This method is experimentally based on a series of creep experiments under tensile load and continuously increasing temperature. Hence, the very accurate strain measurement under constant creep loads combined with effective specimens heating are decisive prerequisites for meaningful results. This application report shows the successful implementation of this method for the direct determination of Tv by the use of the Anton Paar Dynamic Mechanical Analyzer (air bearing-based Modular Compact Rheometer (MCR) with an additional lower linear drive).

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