Nascent phase separation and crystallization kinetics of an iPP/PEOc polymer alloy prepared on a single multicatalyst reactor granule

The crystalline morphology and the liquid-liquid phase separation (LLPS) of an isotactic polypropylene/poly(ethylene-co-octene) (iPP/PEOc) polymer alloy prepared on a single multicatalyst reactor granule were studied by polarized optical microscope, phase contrast optical microscope, and scanning electron microscopy (SEM). We found that the LLPS process had a dominant effect on the final crystalline morphology of the iPP/PEOc polymer alloy. As the LLPS time was increased at 160 degrees C, more and more elastomer component was dispersed uniformly in the iPP spherulites as droplets, instead of being rejected to the outside and concentrated at the boundaries of the spherulites, when the sample was isothermally crystallized at 140 degrees C. The morphologies can be explained by the phase separation and crystallization kinetics. By simply changing the LLPS time, we could control the size of the elastomer droplets (for example between 1 and 10 mu m) that dispersed in the iPP spherulites. Meanwhile, a special structural feature which had different iPP spherulites linked together by numerous iPP fibers separated by interconnected elastomer domains was observed by SEM. This in-reactor blending/alloying process provides a new initial state (nascent state) which is not obtainable by conventional solution blending or extruder blending processes for the study of phase separation and crystallization processes in a polyolefin alloy and also provides a flexible and maybe better way to control the structure, dispersion, and finally the properties of elastomer toughened iPP alloys in application.