Influence of the morphology and viscoelasticity on the thermomechanical properties of poly(lactic acid)/thermoplastic polyurethane blends compatibilized with ethylene-ester copolymer Giordano Pierozan Bernardes , Nathália da Rosa Luiz, Ruth Marlene Campomanes Santana, Maria Madalena de Camargo Forte Laboratory of Polymeric Materials (LaPol), School of Engineering, Federal University of Rio Grande do Sul (UFRGS), P.O. Box 15010, 91501-970, Porto Alegre, State of Rio Grande do Sul, Brazil Correspondence to: G.P. Bernardes (E-mail: giordano.bernardes@ufrgs.br) ABSTRACT: Viscoelastic, interfacial properties, and morphological data were employed to predict the thermal and mechanical properties of compatibilized poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends. The combination of interfacial thickness measured by con- tact angle and entanglement density determined by dynamical mechanical analysis analyze data was employed to evaluate the mechanical behavior of PLA/TPU blends with and without ethylene-butyl acrylate-glycidyl methacrylate (EBG) compatibilization agent. The PLA/TPU blend (70/30 wt %) was prepared in a Haake internal mixer at 190  C and compatibilized with different contents of EBG. The evaluation of the interfacial properties revealed an increase in the interfacial layer thickness of the PLA/TPU blend with EBG. The scanning electronic micros- copy images showed a drastic reduction in the size of the dispersed phase by increasing the compatibilizer agent EBG content in the blend. The compatibilization of the PLA/TPU blends improved both the Izod impact strength and yield stress by 38 and 33%, respectively, in comparison with neat PLA/TPU blend. The addition of EBG into PLA/TPU blends significantly increased the entanglement density and the PLA toughen- ing but resulted in a decrease of PLA deformation at break. The PLA and TPU glass transitions were affected by the EBG, suggesting that the PLA and TPU domains were partially miscible. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48926. KEYWORDS: biodegradable; elastomers; morphology; surfaces and interfaces; structure–property relationships Received 5 September 2019; accepted 22 December 2019 DOI: 10.1002/app.48926 INTRODUCTION Poly(acid lactic) (PLA) is currently one of the most important and employed biodegradable polymers 1 obtained from renewable resources. 2 PLA is notable for its high elastic modulus and stiffness, 3 as well as biocompatibility and biodegradability. 4 How- ever, drawbacks such as brittleness and low thermal stability, 5 as well as low heat deflection, 6 require PLA be modified to fulfill project requirements, especially for physical properties. These changes can be done through bulk modification (copolymeriza- tion), crosslinking, and blending, as reported by Saini et al. 7 Polymer blending, in contrast to other routes, is the most usual option for improving PLA mechanical properties, especially as it enables a better balance of the tensile strength and toughness. In general, PLA is blended with thermoplastic elastomers (TPEs) such as thermoplastic polyurethane (TPU), ethylene-based elastomers (for instance, ethylene-vinyl acetate (EVA), 8 ethylene- acrylic acid copolymer (EAA), 9 and ethylene-methyl acrylate- glycidyl methacrylate (EMAGMA) 10 ) and polyesters (i.e., poly (butylene adipate-terephthalate) (PBAT) 11 and poly(butylene succinate) (PBS) 12 ). The incorporation of flexible polymers, espe- cially TPEs, decreases the PLA elastic modulus and increases both impact absorption and deformation at break. Jia et al., 13 in a study about PLA/TPU blends reinforced with mica, revealed that 50 wt % of TPU reduced the PLA tensile modulus from 240 to nearly 120 MPa and increased the PLA deformation at break from around 30% to approximately 810%. TPE also tends to increase the polymer matrix chain entanglement density due to higher vis- cosity and stronger intermolecular forces. Oommen et al. 14 investi- gated natural rubber (NR)/poly(methyl methacrylate) (PMMA) (50/50 wt %) blends compatibilized with NR-g-PMMA and reported an entanglement density increase from 761 to 729 mol m -3 by adding 5% of NR-g-PMMA. The higher entanglement density was due to the compatibilization agent reducing the interfacial tension and promoting a better adhesion between the phases. The mechanical performance of a polymer blend during its appli- cation is influenced by the thermodynamic and intermolecular © 2020 Wiley Periodicals, Inc. 48926 (1 of 11) J. APPL. POLYM. SCI. 2020, DOI: 10.1002/APP.48926