PHASE-BEHAVIOR OF ISOTACTIC POLYPROPYLENE-POLY(ETHYLENE ETHYLETHYLENE) RANDOM COPOLYMER BLENDS/

The melt-state phase behavior of isotactic polypropylene (i-PP) blende d with a series of poly(ethylene/ethylethylene) random copolymers has been investigated using small-angle neutron scattering (SANS). These P EExx copolymers, where xx is the percentage of ethylethylene (EE) unit s, were prepared by hydrogenation of anionically polymerized polybutad ienes with controlled amounts of 1,2 addition. Random phase approximat ion (RPA) fits to the scattering data for blends of i-PP with a deuter ated, low molecular weight PEE90 at 180 degrees C indicate a statistic al segment length for i-PP that is 10% less than that reported previou sly. Scattering from blends of i-PP with higher molecular weight PEE90 and PEE73 at 180 degrees C can be quantitatively fit using the RPA th eory with chi as the only adjustable parameter, indicating melt miscib ility. PEE46 and PEE62 are strongly and marginally immiscible, respect ively, with i-PP at 180 degrees C. These results establish a ''window' ' in EE content in which these random copolymers can form single phase mixtures with i-PP.