Files in this item



application/pdf9021759.pdf (4MB)Restricted to U of Illinois
(no description provided)PDF


Title:Oriented polymer crystal growth from flowing solutions
Author(s):Spevacek, John Anthony
Doctoral Committee Chair(s):McHugh, Anthony J.
Department / Program:Chemical Engineering
Discipline:Chemical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Polymer
Engineering, Materials Science
Abstract:The kinetics of dilute solution flow-induced crystallization in a tubular flow geometry have been quantified for several polymer systems using digital image processing to observe and monitor the birefringence of the crystallizing fiber. Three molecular weights of polyethylene were studied in 0.01 wt% xylene solutions as well as solutions of polypropylene in decalin and solutions of polystyrene in xylene. Crystallization was studied over a range of temperatures and flowrates and was found to always occur by a two-step process with a highly concentrated amorphous polymer phase forming first, followed later by crystallization. The kinetics were observed to follow the Avrami equation. The time exponent, n, was found to have values around 2, while the constant, k/X$\sb\infty$, was found to show the predicted temperature dependency for nucleation and growth kinetics, i.e. proportionality to exp($-$T$\sb\infty$/T$\sb{\rm x}\Delta$T). It was found that the melting point elevation predicted from theories of strain-induced crystallization could not be used to explain the rapid kinetics of crystallization. Consequently, a theory was developed which allowed the observed solution velocity effects to be included into the Avrami equation thereby yielding a quantitative explanation for the role of flow in the crystal nucleation and growth process. Work with amorphous polystyrene showed the initial unoriented phase separation step occurring, although the phase appeared to be a swollen gel. Further work on the precursor and its formation is crucial to advancing knowledge in this area.
Issue Date:1990
Rights Information:Copyright 1990 Spevacek, John Anthony
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9021759
OCLC Identifier:(UMI)AAI9021759

This item appears in the following Collection(s)

Item Statistics