Design and Performance of Salami-Structured Polymer Alloys by Reactive Blending: Toward Light-Weight, Superior-Toughness, and High-Strength Materials

Abstract Design of polymer alloys that combine lightweight, high-strength, and superior toughness has been a long-standing motivation toward emerging technologies while still facing ongoing challenges. Inspired by the unique salami microstructure in commercial HIPS, here, we present a feasible strategy to construct salami morphology by exploiting the disparities in melting points (Tm) of polymers using conventional reactive processing method. Taking maleic anhydride-grafted poly(styrene-ethylene/butyl diene-styrene) (SEBS-g-MAH) toughened polypropylene (PP) system as an example, we attempt to use polyamide 6 (PA6), with its higher Tm (220 °C), as the rigid multicores within soft SEBS-shells by processing at an intermediate temperature between the Tm of matrix and subinclusions. Specifically, the premade SEBS-g-PA6 via reactive blending was incorporated into PP via melt compounding at 190 °C. Distinct from the traditional procedure, PA6 grafts exhibited solid-like behaviors during blending, effectively “locking” the migrations of PA6 segments to achieve multiple cores within the elastomeric particles. Through the introduction of subinclusions, we demonstrate a synergistic improvement of toughness (51.4 kJ/m2), stiffness (0.86 GPa), and desirable strength (33.6 MPa) while maintaining lightweight (low density of 0.92 g/cm3) for the salami structured alloys. This work resolves the challenge of the persistent performance trade-off of materials, providing a versatile and efficient paradigm for designing high-performance all-polymer alloys.