Design for disassembly of composites and thermoset by using cleavable ionic liquid monomers as molecular building blocks

Aircraft, automotive industries and the increasing numbers of wind turbine blade lead to a huge amount of carbon fiber reinforced polymers requiring to be recycled and/or reused in a closed loop supply chain or circularity of materials. Herein, we have designed and synthesized a tetra-epoxidized imidazolium ionic liquid (Tetra-IL) monomer containing ester-cleavable groups. This monomer was incorporated as a molecular brick platform into conventional epoxy-amine networks in order to tailor the physical properties as well as the end-oflife of the resulting networks. Thus, the introduction of only 10% of IL-based comonomers significantly reduced the gel time by 85% opening perspectives in the field of fast-cure epoxy resins. Overall, all the networks designed in this work presented high thermal stability (>350 degrees C), higher Tg included between 180 and 230 degrees C combined with hydrophobic behavior. Increasing the amount of IL monomer in the networks improved the homogeneity of thermosets and wettability of the epoxy resins with the carbon fibers (CF). Most importantly, the use of Tetra-IL led to the development of degradable networks under mild conditions within a brief timeframe (4.5 h) and allowing to recover the carbon fibers. In summary, this study highlighted the great potential of IL-based comonomers as molecular brick into conventional epoxy thermosets as a promising strategy to tailor the physical properties versus sustainability/degradability for the development of high-performance thermosets and composites.

Automated summary

The increasing demand for recycling and reusing carbon fiber reinforced polymers in various industries prompted the design and synthesis of a tetra-epoxidized imidazolium ionic liquid (Tetra-IL) monomer. This monomer, when incorporated into conventional epoxy-amine networks, improved the physical properties and end-of-life of the resulting networks. The introduction of only 10% of IL-based comonomers significantly reduced gel time and opened up possibilities for fast-cure epoxy resins.