Toughening of polypropylene with crystallizable poly(ethylene oxide)

A crystallizable polymer, poly(ethylene oxide) (PEO), was used as new modifier to tailor the toughness of isotactic polypropylene (iPP). An optimum performance was achieved at a medium PEO content of 15 wt% where the toughness was enhanced by 300%, while the strength only decreased slightly. To elucidate the origin of toughening in the iPP/PEO blends, various crystallographic and morphological experiments including X-ray diffraction, electron microscopy and calorimetry were adopted to explore the dependences of polymorphic composition and crystallized morphology on PEO content. When the PEO content is less than 15 wt%, the dispersed PEO cannot crystallize, and these non-crystalline PEO microspheres are embedded in both alpha- and beta-form iPP spherulites, which is mainly responsible for the toughening. In contrast, when the PEO content is higher than 15 wt%, the PEO phase becomes crystallizable, and significant phase segregation takes place, resulting in a marked deterioration in mechanical properties. (C) 2011 Society of Chemical Industry