ORIGINAL PAPER Structure–property relationships in ternary polymer blends with core–shell inclusions: revisiting the critical role of the viscosity ratio Omid Moini Jazani 1 & Vahabodin Goodarzi 2 & Farkhondeh Hemmati 3 & Mohammad Reza Saeb 4 Received: 21 June 2016 /Accepted: 4 October 2016 # Springer Science+Business Media Dordrecht 2016 Abstract Structure–property relationship in typical polypro- pylene/polycarbonate/poly[styrene-b-(ethylene-co-butylene)- b-styrene] (PP/PC/SEBS) ternary blends containing maleated SEBS (SEBS-g-MAH) was investigated. Three grades of PC with different melt viscosities were used, and changes in blend morphology from PC/SEBS core–shell particles partially surrounded by SEBS-g-MAH to inverse SEBS/PC core–shell particles in PP matrix were observed upon varying the viscos- ity ratio of PC to SEBS. It was found that the viscosity ratio completely controls the size of the core–shell droplets and governs the type, population, and shape of the dispersed do- mains, as evidenced by rheological, mechanical, and thermomechanical behavioral assessments. Dynamic mechan- ical analysis of samples with common (PC–SEBS) and in- verse (SEBS–PC) core–shell particles revealed that they show completely different behaviors: blends containing PC–SEBS presented a higher storage and loss modulus, while blends containing SEBS–PC exhibited a lower β-transition tempera- ture. Moreover, ternary blends with PC cores showed the highest Young’s modulus values and the lowest impact strength, due to the different fracture modes of the blends containing PC–SEBS and SEPS–PC core–shell droplets, which present debonding and shell-fracture mechanisms, re- spectively. Morphological observations of blends with high- molecular-weight PC demonstrated the presence of detached droplets and rods of PC in the PP matrix, along with compos- ite core–shell and rod-like particles. Micrographs of the frac- ture surfaces confirmed the proposed mechanisms, given the presence of stretched (debonded) PC (SEBS) cores encapsu- lated by SEBS (PC), which require more (less) energy to achieve fracture. The correlation between the mechanical and morphological properties proves that decreasing core di- ameter and shell thickness has positive effects on the impact strength but decreases the Young’ s modulus. Keywords Core–shell morphology . Viscosity ratio . Thermomechanical behavior . Ternary blends . Mechanical properties Introduction Multicomponent polymer blends are of great interest because of their potential to display diverse morphologies, which makes them promising materials for applications requiring a wide range of mechanical properties. In this context, our understand- ing of the relationships between a blend’ s microstructure and its mechanical properties is of critical importance [1–4]. The effects of material/processing parameters such as polymer type, blend composition, melt viscosity, and/or elasticity ratio, inter- facial tension, and shear rate on the morphologies of polymer blends have been addressed in diverse studies [5, 6]. It is as clear as crystal for those working in the filed that polymer blends are mostly immiscible and show bi- or triphasic mor- phologies owing to the high molecular weights of their polymer * Omid Moini Jazani o.moini@eng.ui.ac.ir * Mohammad Reza Saeb saeb-mr@icrc.ac.ir 1 Department of Chemical Engineering, College of Engineering, University of Isfahan, Isfahan, Iran 2 Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, P.O. Box 19945-546, Tehran, Iran 3 Caspian Faculty of Engineering, College of Engineering, University of Tehran, 43841-119, Rezvanshahr, Guilan, Iran 4 Department of Resin and Additives, Institute for Color Science and Technology, P.O. Box: 16765-654, Tehran, Iran J Polym Res (2016) 23:231 DOI 10.1007/s10965-016-1116-0