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Title:A study of transient flow-induced crystallization of polymer melts
Author(s):Bushman, Alexander Craig
Doctoral Committee Chair(s):McHugh, Anthony J.
Department / Program:Chemical and Biomolecular Engineering
Discipline:Chemical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Polymer
Engineering, Chemical
Abstract:Flow-induced crystallization of several polymer systems has been studied using a four-roll mill device, coupled with optical polarimetry, to provide an in-situ technique for monitoring the transformation kinetics both during and following flow. The use of a crystallizable droplet phase, suspended within a non-crystallizable carrier phase, prevents die blockage and allows for direct measure of the droplet phase kinematics. Both birefringence and dichroism are used to investigate the crystallinity development within the deforming droplet. Birefringence studies suggest that the initial rate of crystallization is a function of both the induced stress and strain within the deformed material. Pre-crystallinity during the flow regime, prior to flow cessation, is required to achieve reproducible stress-strain behavior. Unlike birefringence studies, the dichroism studies allowed the study of the transient crystallization occurring during the flow regime. Induction times to crystallinity were found to correlate with the extension rate during the deformation. Rheological studies of the polymer systems were performed, wherein viscoelastic data and relaxation time constants were determined. A theoretical model for flow-induced crystallization was developed using a modified strain-induced crystallization model, coupled with the Hamiltonian Bracket formalism, to account for the dynamics of flow. A variety of flow kinematics and their effect on flow-induced crystallization are modeled. A non-linear force factor is incorporated to account for the finite extensibility of the molecule. The model is compared to experimental data and does predict qualitatively the effects of the flow field on crystallization.
Issue Date:1995
Rights Information:Copyright 1995 Bushman, Alexander Craig
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9624297
OCLC Identifier:(UMI)AAI9624297

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