Elongated soy protein isolate-poly(D, L-lactide-co-glycolic acid) microcapsules prepared using syringe filters and their effect on self-healing efficiency of soy protein-based green resin

A self-healing soy-based resin filled with soy protein isolate (SPI) containing poly(D, L-lactide-co-glycolic acid) (PLGA) microcapsules (MCs) was prepared. MCs were prepared using a syringe filter via a membrane emulsification technique. Using this method, spherical (diameter of about 1.30 μm) and elongated MCs (aspect ratios up to 20) could be produced. Tensile properties and self-healing efficiencies of resins were characterized for both MC morphologies in terms of strength recovery and toughness recovery. While both MCs could successfully heal cracks, spherical MCs were seen to compromise the tensile properties of the resin, whereas elongated MCs demonstrated some mechanical enhancement. Overall results showed that elongated MCs having a higher aspect ratio resulted in slightly better self-healing performance as well as a mechanical improvement. The results also show that higher MC loading results in higher self-healing efficiency.