Order-Disorder Melt Transformation, Hierarchical Multiphase Separation and Transition, Complex Crystal Polymorphism and Self-Toughening of Isotactic Polypropylene/Poly(1-butene) Blends

A sequential annealing, subsequent crystallization and melting procedure (SA-SMC) is developed to characterize the order–disorder melt transformation at TO-D of 190–200 °C and the corresponding temperature- and time-dependent hierarchical multiphase separation and transformation in melt-compounded isotactic polypropylene/poly(1-butene) blends. Rheological measurements confirmed the transition from an ordered melt with extended random coils to a disordered melt with quasi equilibrium globular chain conformations. Thermodynamically unstable and metastable β-form crystals of the iPP phase with a content of 44–97 wt% are generated in situ from the ordered melts without the addition of β-nucleators. Self-nucleation at 170 °C and macro-phase segregation in the melt unexpectedly result in -form crystallization in the iPP phase. Confined crystallization in the iPB nanophase favor the formation of Form I crystals. Moreover, the blends exhibit scalable self-toughened mechanical properties via synergistic control of the β-phase proportion and nano/mesophase separation. The threshold domain size of the dispersed iPB phase is less than 2 μm for tensile ductile–brittle transformation.