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

Abstract

Ethene/propene terpolymers containing either 1-vinylcylohexene-4 (VCHen) or vinylcyclohexane (VCHan) as termonomer component were prepared using MAO-activated rac-Me 2 Si(2-MeBenz[e]Ind 2 ZrCl 2 (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(DM) 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.