Elongational Flow-Induced lamellar Rotation Observed in a Polystyrene-block-Poly(ethylene propylene) Diblock Copolymer

초록

The lamellar forming diblock copolymer, polystyrene-block-poly(ethylene propylene) (SEP) has been also investigated. The disordered lamellar domains of compression molded SEP samples were also aligned in a preferred direction by roll-casting at 200 oC. In EFOR measurement, uniaxial elongation has been applied at 180 oC with a Hencky strain rate, , of 0.01 sec-1 in the direction either parallel (denote Case I) or perpendicular (Case II) to the direction of the lamellar normals. The apparent retardation, Rapp, and initial moduli measured during the early stage of elongation, either PS or PEP domain is preferentially elongated. Transient elongational viscosity, , measured during the Case I elongation exhibits a continuous increase up to rupture, indicating the absence of the morphological change during elongation. One measured during the Case II elongation shows an initial increase up to t ~ 20 s, followed by a gradual decrease of its increase rate up to 80 s, prior to a final prominent increase before rupture.