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• Thermal and flame retardant properties of recyclable disulfide based epoxy vitrimers

  A. Rekondo, A. huegun, V. Berner, C. Höhne, L. Hammer

  Materiales Compuestos (2026). Vol. 09 - Comunicaciones MatComp25 (2025), (Núm. 4 Nuevos Materiales), 28

  
  

  Abstract

  The development of flame-retardant epoxy vitrimers which are suitable for use as a composite matrix material is essential for the transition to a sustainable circular economy. In this work the thermal and flame-retardant properties as well as the rheological characteristics of epoxy vitrimers based on 4-Aminophenyldisulfide (4-AFD) hardener and with different reactive and additive Phosphorus based flame retardants (FR) with different oxidation states were studied. The use of 4-AFD as curing agent imparts vitrimeric properties to the material and allows repairing, reprocessing and recycling. A series of epoxy vitrimers (EV) were prepared aiming to improve the flame-retardant properties while maintaining dynamism and reprocessability. The neat EV (Tg ∼125 °C) showed a limited oxygen index (LOI) of 20.9 ± 0.4 %O2 and no classification and heavy dripping in the UL-94 vertical burning test. With 1.5 wt% of Phosphorous (P) in the EV, LOI values up to 38.5 ± 0.4 %O2 and V-0 classification with excellent self-extinguishing behavior was achieved. Especially gas phase active FRs with lower oxidation states showed better flame-retardant properties in the LOI and UL-94 vertical burning tests with identical phosphorus content. In cone calorimeter test the EVs with 1.5 wt% P reduced the peak heat release rate (PHRR) up to 43 %. The addition of reactive phosphorous-based FRs did not influence the dynamism and recyclability of the material in dynamic mechanical analysis. After mechanical recycling >73 % of the mechanical strength was recovered and the flame retardant EVs do reach as well a V-0 classification in the UL-94 vertical burning test.

  Abstract
  The development of flame-retardant epoxy vitrimers which are suitable for use as a composite matrix material is essential for the transition to a sustainable circular economy. In [...]

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