A strategy for biomass-derived matrix with facile moulding and closed-loop recycling capabilities

Developing polymer matrices with closed-loop recyclability is a key solution to solve the sustainability issues caused by unrecyclable end-of-life multi-phase composites, and using building blocks from renewable resources rather than petrochemical products presents an attractive option. However, the strategy of first extracting monomers from biomass feedstocks and then polymerizing them is functionality-removed, complexity-increased, and energy-inputted. We report a strategy demonstration from current polymer-monomer-matrix mode to polymer-macromolecule-matrix, based on retaining the advantages in property, processing, and recycling of silk protein. The silk matrix as was its fiber-reinforced composite show spontaneously room-temperature molding and curing capabilities, totally avoiding the use of any additives. The obtained composites also possess high mechanical property and environmental durability. Moreover, the multicycle recyclability of composites could be achieved by a simple room-temperature dissolution procedure, acquiring lossless reinforcing fibers and reusable silk protein. Conventional carbon fiber composites require high temperature curing and have complex recycling procedures. Here, the authors report high strength silk fibroin carbon fiber composites which are synthesized and recycled via room-temperature solvent-based methods.