l-Lysine templated CaCO3 precipitated to flax develops flowery crystal structures that improve the mechanical properties of natural fibre reinforced composites

We describe how the mechanical properties of natural fibre composites can be improved by precipitating coral-like coatings to the surfaces of reinforcing fibres. We consider three amino-acid templates (l-lysine, glycine and ββ-alanine) on calcium carbonate growth to natural fibres. l-Lysine forms reticulate flower-like crystals, ββ-alanine forms globular crystals and glycine forms blocky crystals. These coralised fibres are used to reinforce styrene butadiene rubber and when compared against untreated-fibre reinforced composites; we find that at sufficiently high concentrations l-lysine templated mineral coatings improve composite strength by more than 100%. Contrarily, ββ-alanine and glycine templated mineral coatings do not improve the composite strength by more than ca. 60% and ca. 40% respectively. Molecular dynamics simulations elucidate the attachment mechanisms for each amino acid and the highest potential is in the l-lysine templated crystals. Finite element analyses reveal the success of l-lysine templated coatings is due to a heightened fibre tractive resistance.