The Crystallization of Polyetheretherketone (Peek) From the Glass
Brennan, John Edward
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https://hdl.handle.net/2142/71854
Description
Title
The Crystallization of Polyetheretherketone (Peek) From the Glass
Author(s)
Brennan, John Edward
Issue Date
1988
Doctoral Committee Chair(s)
Geil, Phillip H.
Department of Study
Metallurgy and Mining Engineering
Discipline
Metallurgical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Abstract
The effects of melt thermal history on the morphology and kinetics of PEEK crystallized from the glassy state have been investigated. Amorphous PEEK crystallized as aggregates of microcrystals when annealed at temperatures ranging from 145$\sp\circ$C to 200$\sp\circ$C. Heterogeneous nuclei remained in the melt, with decreasing numbers as a function of melt time and temperature, for up to at least ten minutes over the melt temperature range examined. Additional nuclei observed at long annealing times were created by a second homogeneous or pseudo-homogeneous process. Intermixing of molecules during long melt times destroyed a chemical segregation imposed in the initial casting of the samples. Segregation effects also contributed to the rates of continued nucleation and growth at long annealing times. The molten state may be described, therefore, as a nonhomogeneous melt containing retained crystalline nuclei, both of which are affected by melt history. An Avrami analysis revealed that PEEK was predominantly nucleated heterogeneously as spherulites when annealed at 162$\sp\circ$C or higher. Diffusion of the chains was the rate controlling process. Melt history affected only the kinetics of the crystallization and not the mechanisms. Graphite fibers had no nucleating effect on the crystallization of PEEK from the glass. Differences in nucleating ability among three fiber types during melt crystallization indicated that PEEK may be nucleated by the matching of the graphitic rings with the PEEK phenyl units.
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