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Crystallization of very low density copolymers of ethylene with α‐olefins
Author(s) -
Minick J.,
Moet A.,
Hiltner A.,
Baer E.,
Chum S. P.
Publication year - 1995
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1995.070580819
Subject(s) - copolymer , differential scanning calorimetry , crystallinity , materials science , crystallization , crystal (programming language) , polymer chemistry , lamellar structure , isothermal process , ethylene , crystallography , thermodynamics , polymer , chemistry , catalysis , organic chemistry , composite material , programming language , physics , computer science
Abstract Differential scanning calorimetry (DSC) was used to analyze the crystal distribution in homogeneous ethylene–octene copolymers polymerized by the constrained geometry catalyst technology (CGCT). To minimize ambiguities from thermal history effects, copolymers were isothermally annealed at temperatures within the melting range. The cumulative crystallinity was related to the crystal distribution by the Gibbs–Thomson equation. The results provided a clear distinction between Type I copolymers (density less than 0.89 g/cc) and Type II copolymers (densities between 0.89 and 0.91 g/cc). The former had a singlecrystal population that was identified with the bundled crystals seen in transmission electron micrographs. In comparison, the latter had two crystal populations that correlated with lamellar crystals and bundled crystals. © 1995 John Wiley & Sons, Inc.