A study of flow-induced crystallization in two-phase polymer melts

The effects of shearing and elongational flows on flow induced crystallization in polymer melts were investigated for the two-phase system of high molecular weight polyethylene suspended in a linear low density polyethylene carrier phase. Shearing flow was produced by a counter-rotating couette device and elongational flow was produced by means of a four roller mill device. Deformation and bursting of droplets were observed in both of these flows, however, shearing flow was found unsuitable for quantitative studies, since the orientation of the optical axes in the carrier and suspended phases were not coaxial. Hot stage and dichroism studies indicated that crystallization occurs in the suspended phase in the four roller mill, at temperatures above which quiescent crystallization would occur. In-situ birefringence measurements were made and initial crystallization rates were determined and found to depend upon both stress and strain in the deforming droplet. This was very suggestive of a viscoelastic phenomenon, not simply, a nucleation and growth controlled mechanism, thus the separability, of flow effects and nucleation and growth crystallization, is brought into question by this complex behavior. A first order approximation based on molecular rheology has been used to gain qualitative and quantitative insights on the observed trends.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Guy, R. Kirk

Contributors dc:contributor

• McHugh, Anthony J.

• Engineering, Chemical

Statement dc:rights

• Copyright 1992 Guy, R. Kirk

Language dc:language

eng

Identifier

AAI9236476
(UMI)AAI9236476

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/22112