Influence of Copolymer Composition and Curing on Toughness of Isotactic Polypropene Blended Together with Metallocene‐EPDM and Ethene/Propene/Vinylcyclohexane Terpolymers

Ethene/propene terpolymers containing either 1‐vinylcylohexene‐4 (VCHen) or vinylcyclohexane (VCHan) as termonomer component were prepared using MAO‐activated rac‐Me₂Si(2‐MeBenze]Ind)₂ZrCl₂ (MBI). Propene content was varied between 26 and 72 wt.‐% with less than 1 mol‐% termonomer incorporation. Blends containing 85 vol.‐% isotactic polypropene (i‐PP) and 15 vol.‐% of the two EP terpolymer families were prepared by melt‐compounding in a twin‐screw kneader at 200°C to examine the role of sulfur‐mediated crosslinking of the unsaturated EPDM terpolymer phase in comparison to the corresponding blends containing non‐crosslinked saturated EP/VCHan terpolymers. The observed glass temperature (T_g) depression of the T_g of EP(D)M phases with respect to the T_g of the corresponding bulk EP(D)M was attributed to the presence of thermally induced stresses in both blend systems. Blends of i‐PP with crosslinked EPDM showed smaller T_g depression with respect to those of iPP/EPM blends containing non‐crosslinked EP and EPM dispersed phases. Morphology differences were detected for i‐PP/EPM and dynamically vulcanized i‐PP/EPDM blends by means of atomic force microscopy (AFM). The crosslinked i‐PP/EPDM blends exhibited significantly improved low temperature toughness as compared to the corresponding non‐crosslinked i‐PP/EPM blends. Curing of the EPDM elastomer phase in i‐PP/EPDM (85 vol.‐%/15 vol.‐%) blends afforded significantly improved toughness/stiffness balance and a wider toughness window with respect to the corresponding i‐PP/EPM and i‐PP/EP blends without sulfur‐cured rubber phases.