Mechanical and optical effects of elastomer interaction in polypropylene modification: Ethylene-propylene rubber, poly-(ethylene-co-octene) and styrene-butadiene elastomers

The interaction between binary combinations of three different elastomer classes commonly applied in impact modification of isotactic polypropylene (iPP) was studied. Blends based on a homogeneous ethylene-propylene (EP) random copolymer (EP-RACO) and a heterophasic EP impact copolymer comprising ethylene-propylene rubber (EPR) with different external elastomer types, one homogeneous ethylene-1-octene copolymer (EOC), and two hydrogenated styrenebutadiene-styrene triblock copolymers (SEBS) with different styrene content, were prepared. The phase morphology, mobility as a function of temperature, mechanical and optical properties were studied. Special effects could be achieved for the combination of two different elastomer types. The results clearly demonstrate the possibility to achieve attractive property combinations in ternary systems consisting of a crystalline PP matrix and two different types of elastomer, EPR or EOC on the one hand and SEBS on the other hand. A combination of density matching and compatibilization effects allows reaching good low temperature impact strength together with a transparency close to matrix level when selecting a butadiene-rich SEBS type

Rheology/morphology interactions in polypropylene/polyamide-6 nanocomposites

Polypropylene/polyamide-6 (PP/PA-6) blends and their nanocomposites with unmodified and organically treated layered silicates (montmorillonite) were prepared in a melt compounding process to explore their mechanical performance. The rheology and morphology of these materials was studied. It could be shown that in all cases the inorganic filler enriched in the PA phase, resulting in a phase coarsening of the PP/PA nanocomposite as compared to the non-filled PP/PA blend. The mechanical properties of these nanoblends are consequently only slightly better than the pure polymers with respect to the modulus, while the impact level is below the pure polymers, reflecting the heterogeneity of the nanoblend