Intrinsic flame retardant phosphonate-based vitrimers as a recyclable alternative for commodity polymers in composite materials

Jens C. Markwart, Alexander Battig, Tobias Urbaniak, Katharina Haag, Katharina Koschek, Bernhard Schartel, Frederik R. Wurm*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

17 Citations (Scopus)
25 Downloads (Pure)


Recycling of crosslinked fiber-reinforced polymers is difficult. Moreover, as they are often based on flammable resins, additional additives are needed. So-called “vitrimers” open the possibility of recycling and reprocessing and repairing with dynamically crosslinked chemistries. To date, vitrimer-based composites still need flame retardant additives, such as organophosphates. An additive-free vitrimer composite has not been reported. Herein, we synthesized an intrinsic flame-retardant vitrimer, relying on vinylogous polyurethanes containing covalently installed phosphonates as flame-retardant units and prepared glass-fiber-reinforced composites. We studied recycling and flame retardant properties and compared the data to phosphorus-free vitrimers and conventional epoxy resins (with and without additive flame retardant). Our phosphonate-based vitrimer proved in first tests, a flame retardant effect comparable to commercial flame retardant resins. The bending strength and bending modulus for the phosphorus-vitrimer glass fiber composites were comparable to glass fiber composites with permanently cross-linked epoxies. In summary, we were able to prove that the covalent installation of phosphonates into vitrimers allows the preparation of recyclable and intrinsic flame retardant composites that do not need flame retardant additives. We believe this concept can be expanded to other polymer networks and additives to generate recyclable and sustainable high-performance materials.
Original languageEnglish
Pages (from-to)4933-4941
Number of pages9
JournalPolymer chemistry
Issue number30
Publication statusPublished - 14 Aug 2020
Externally publishedYes


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