Oriented polymer crystal growth from flowing solutions

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.

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

• Spevacek, John Anthony

Contributors dc:contributor

• McHugh, Anthony J.

• Chemistry, Polymer
• Engineering, Materials Science

Statement dc:rights

• Copyright 1990 Spevacek, John Anthony

Language dc:language

eng

Identifier

AAI9021759
(UMI)AAI9021759

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/22099