Structure Formation and Crystallization in Two-Phase Polymer Blend Flows (Fibers, Polyethylene, Polypropylene)
Sakellarides, Stefanos L.
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https://hdl.handle.net/2142/69772
Description
Title
Structure Formation and Crystallization in Two-Phase Polymer Blend Flows (Fibers, Polyethylene, Polypropylene)
Author(s)
Sakellarides, Stefanos L.
Issue Date
1986
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Abstract
Flow induced crystallization of high density polyethylene and polypropylene has been studied in a two-phase flow system using linear low density polyethylene as the carrier phase. Extensional stresses were generated under slow flow conditions by either of two methods: one involving flow past a stationary seed, the other involving a droplet deformation and bursting mechanism. In both cases, oriented, fibrillar crystallization of the high density phase was observed optically and correlated with calculations indicating the presence of flow-induced extensional gradients. Morphological, thermal, and birefringence data indicate that the crystalline fibers produced are oriented and superheatable, and consist of a multifibrillar substructure. For fibers produced by the droplet bursting process a semi-quantitative agreement was found between fiber melting point and birefringence based on the simplified analysis for the bursting induced extensional flow. These results demonstrate that two-phase flows of crystallizable systems are a convenient means for studying the phenomenon of flow induced crystallization in polymer melts.
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