Sustainable Carbon Fiber Composites Based on Recyclable Bio‐Based Vanillin Thermoset Polymers

ABSTRACT Although bisphenol A (BPA) is the most used organic compound in the production of thermosets for composite materials, there has been an urgent scientific concern to eliminate it in the last years due to the environmental issues raised by the difficulty of repairing, recycling or reprocessing these materials, together with the endocrine‐disrupting effect and toxicity to living species. As an approach to solve these issues, a series of bio‐based monomers with different epoxy content were synthesized from vanillin‐derived compounds. The incorporation of covalent adaptable networks (CANs) was investigated through the polymerization of these monomers with dynamic hardeners (aminophenyl disulfide, 2‐AFD, and 4‐AFD) to provide the resulting thermosets with reprocessing and recycling properties. The optimal curing cycle was investigated, and the resulting vitrimers were characterized in terms of chemical and thermal properties. Subsequently, these materials were mechanically recycled and reprocessed, wherein lower temperatures and pressures were applied in the bio‐based systems in comparison to those employed in the petrol‐derived vitrimers. Finally, a composite laminate was consolidated with these biobased thermosetting resins to develop a rapid manufacturing process through their reprocessing ability. The interlaminar shear strength (ILSS) showed a dependence on the epoxy functionality, with a significant increase observed in the bi‐functional epoxy system compared to the mono‐functional vitrimer. The results of the thermomechanical tests demonstrated that the reprocessing process did not affect the values of the glass transition of the composites, thus opening a way for further recycling or reprocessing of the resulting composite even during and after its operational lifetime.