Fracture behaviors of isotactic polypropylene/poly(ethylene oxide) blends: Effect of annealing

As a part of serial work about the toughening of isotactic polypropylene (iPP) during annealing treatment, this work reports the effect of annealing on fracture behaviors of iPP blend with a little of poly(ethylene oxide) (PEO). Injection-molded bars of an iPP/PEO blend were annealed at different temperatures (50–160 °C) for 12 h and at 100 °C for different durations (12–96 h). The fracture behaviors of the annealed samples, including notched Izod impact fracture, universal tensile fracture, and single-edge notched tensile (SENT) fracture, were comparatively investigated to establish the role of annealing in improving the fracture resistance of the sample. The results showed that the annealing treatment greatly influences the fracture resistance of the blend. The impact-fractured surface morphologies were characterized by scanning electron microscope (SEM) to clarify the possible mechanisms for the improvement of the fracture resistance. It was proposed that, the excellent fracture resistance of iPP with a minor phase of which exhibits relatively low melting temperature can be easily achieved through the simple annealing treatment, even if the minor phase is immiscible with iPP.

► Immiscible polypropylene/poly(ethylene oxide) was annealed at different temperatures (50–160 °C) for 12 h and at 100 °C for different durations (12–96 h).
► Fracture behaviors of the annealed samples were systematically investigated by means of various measurements.
► In a range of annealing temperature (100–140 °C), largely improved fracture resistance was observed.
► Annealing treatment is favorable for the improvement of the storage modulus of the immiscible polymer blend.