Miscibility of isotactic polypropylene/ethylene-propylene random copolymer binary blends

Miscibility for blends of isotactic polypropylene (PP) and ethylene-d4−propylene random copolymer (EPR)s prepared by copolymerization of propylene and perdeuterated ethylene with metallocene catalyst has been investigated by small-angle neutron scattering (SANS). SANS experiments were conducted for the blends of PP with EPRs containing 19 mol % (D-EPR19) and 47 mol % (D-EPR47) of deuterated ethylene unit at various temperatures. SANS results indicated that most of the blends are in the homogeneous one-phase mixture, and the Flory−Huggins interaction parameter χ analyzed by the random phase approximation is approximately 5.0 × 10-3 for the PP/D-EPR47 blend while it is very small and within the range −1.0 × 10-3 ≤ χ ≤ 1.0 × 10-3 for the PP/D-EPR19 blend. It was also revealed that χ does not change with temperature meaningfully within the temperature range 440 ≤ T ≤ 482 K, while phase separation due to crystallization of PP was observed at 373 K. No domain structure of EPR whose size is in the range of an op...