Synchrotron Studies and Computational Modeling of Flow-Induced Polymer Crystallization in Shear and Extensional Flow

Polymers are used in the manufacturing of products that permeate all facets of life. Many of the most widely used thermoplastic materials are semi-crystalline; that is, they solidify into their final, usable form via crystallization from the melt. Flow fields encountered during processing have a profound affect on crystallization rate, and can fundamentally modify structure and properties of the resulting product owing to induced orientation of molecules and crystallites. This proposal outlines a systematic study of this so-called 'flow-induced crystallization' (FIC) phenomenon. Unique aspects of the proposed research are: (i) application of powerful in situ synchrotron-based x-ray scattering methodologies to study both crystallization kinetics and development of morphological state and orientation at both the atomic and semi-crystalline lamellar levels; (ii) integration of studies employing well-defined homogeneous shear and uniaxial extensional deformations, to more fully explore the range of kinematics present in the most important types of polymer processing operations; and (iii) coordination of experimental studies with computational modeling, to allow direct testing of the critical link in FIC models between molecular orientation and enhanced crystallization kinetics and evaluate the potential of models for use in process simulation.