Compatibilization effects in thermoplastic protein/polyester blends

Novatein thermoplastic protein was extrusion blended with poly(butylene adipate-co-terephthalate) (PBAT) in the presence of dual compatibilizers to produce blends with greater energy absorbing properties than pure Novatein. Compatibilizer pairs were Joncryl ADR-4368 (glycidyl methacrylate-functionalized) with 2-methylimidazole (2MI), and poly-2-ethyl-2-oxazoline (PEOX) with polymeric diphenyl methane diisocyanate (pMDI). Uncompatibilized Novatein/PBAT blends had decreased tensile mechanical properties, attributed to phase separation, and poor interfacial adhesion. PBAT became finely dispersed in both compatibilized systems, but PEOX/pMDI blends showed embrittlement and large Novatein domains, which acted as stress concentrations. Tensile strength and elongation at break for Joncryl/2MI blends did not decrease compared with Novatein, even at 10 wt % PBAT, and impact strength increased threefold. Dynamic mechanical analysis and solvent extraction showed that PBAT coalesced in all systems, at compositions as low as 2 wt %. It was concluded that using Joncryl/2MI as a dual compatibilizer system can successfully produce a morphology that enhances energy absorption during fracture. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45808.