Authors: Mohit Mamodia Kishore Indukuri Edward T Atkins Wim H De Jeu Alan J Lesser
Publish Date: 2008/11/01
Volume: 43, Issue: 22, Pages: 7035-7046
Abstract
We report on the deformation behavior of commercially relevant lamellar and cylindrical triblock copolymers poly styrenebethylenecobutylenebstyrene SEBS with two different compositions The structural changes that occur at various length scales have been studied using a simultaneous small and wideangle Xray scattering SAXS/WAXS during uniaxial tensile deformation of the polygrain samples SAXS provides information about changes that occur upon deforming the glassy cylindrical or lamellar PS domains WAXS on the other hand is sensitive to the crystallographic structure of the rubbery midblock Deformation calorimetry has been used to determine the energetics involved The combined results from the various techniques indicate that the deformation takes place in three stages First at small strains dilation occurs in the rubbery phase At intermediate strains the hard lamellar or cylindrical domains undergo microbuckling which is associated with a downturn in the stress–strain curve Finally we interpret that at higher strains the bent lamellar/cylindrical domains rotate in the stretching direction resulting in a significant shear on the rubbery midblock This in turn leads to straininduced crystallization in these materials Although we could not prove it by WAXS deformation calorimetry which is more sensitive than the WAXS was utilized to show its presenceThe authors thank Center for University of Massachusetts and Industry Research on Polymers CUMIRP ClusterM and Kraton Polymers U S LLC for their support and the National Science Foundation Materials Research Science and Engineering Center for their financial support
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