Manipulating morphology in thermoplastic protein/polyester blends for improved impact strength

Abstract

Novatein thermoplastic protein was blended with 10 wt% poly(butylene adipate- co- terephthalate) (PBAT) compatibilized with Joncryl ADR- 4368 and 2- methylimidazole (2MI). Morphology was tailored for favorable impact strength through changing vis-cosity ratio (λ) and interfacial tension (γ12). For uncompatibilized blends, λ decreased and γ12 increased with increasing Novatein water content, whereas compatibilizers caused a decrease in both λ and γ12. PBAT continuity was high when uncompatibi-lized, but dispersion improved with decreasing λ and increasing γ12. The dispersed domain size decreased in all compatibilized blends; PBAT continuity was lowest in samples with the smallest λ. Compatibilized blends had higher impact strength than Novatein and uncompatibilized blends through improved interfacial adhesion, smaller domain size, and increased dispersion. By altering λ and γ12, and with ap-propriate chemical interaction, a morphology can be created for improved impact strength. Increasing PBAT content showed further increases in impact strength; however, a cocontinuous morphology formed, demonstrating that composition can override the effect of λ and γ12.