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

Abstract

Self-healing soy-based resins with soy protein isolate (SPI) containing poly(D, L-lactide-co-glycolic acid) (PLGA) microcapsules (MCs) were prepared. Spherical (diameter of 1.30 μm) and elongated MCs (aspect ratios up to 20) were produced using a membrane emulsification technique using syringe filters. Self-healing efficiencies of resins were characterized for their 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. For resins with elongated MCs, self-healing efficiencies of about 45% and 41% in terms of strength recovery and toughness recovery, respectively, were obtained. For spherical MCs, the self-healing efficiencies were even higher. However, these higher efficiencies were a result of the compromised tensile properties of the resin. The results also showed that higher MC loading results in higher self-healing efficiency. Use of self-healing green resins can extend the useful life of green composites as well as enhance their safety, thus, allowing them to replace currently used petroleum-based composites in many applications.