Control of Chain Orientation in Blends of Polypropylene and Polybutene‐1

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An extruded sheet having unique molecular orientation is developed using a miscible blend of isotactic polypropylene (PP) and isotactic polybutene‐1 (PB). Blends containing a small amount of N,N′‐dicyclohexyl‐2,6‐naphthalenedicarboxamide are extruded from a ribbon‐shaped die onto a chill roll at various temperatures. It is found that form‐I crystals of PB become oriented in the flow direction, whereas β‐form crystals of PP become oriented perpendicular to the flow direction. The molecular orientation is the most obvious for the blend containing 60 wt% of PB extruded at a chill roll temperature of 80 °C. The anisotropy in the tensile modulus of the obtained extruded sheet is reduced by its extraordinary molecular orientation. image