(201a) Early Structure Development during Flow-Induced Crystallization of Bimodal Blends of Model Isotactic Polypropylenes

Studies of structure and morphological development during shear-induced crystallization of model blends of isotactic polypropylene (iPP) were performed using in-situ rheo-optical (birefringence and turbidity) and x-ray scattering measurements (SAXS and WAXD). Binary blends were prepared in which a high molecular weight fraction of iPP (L-PP, 3500 kg/mol) with narrow molecular weight distribution was blended with lower molecular weight metallocene iPP (Base-PP, 186 kg/mol). A new method for isolating the signal arising from a given depth at each time point during flow-induced crystallization using real time rheo-optical and x-ray scattering measurements has enabled us to confirm several existing results and has unveiled several new keys on propagation of threadlike precursors. The impact of the concentration of long chains on the anisotropic crystalline development will also be discussed.