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Crystallization behavior of poly( N ‐methyldodecano‐12‐lactam). IV. Nonisothermal crystallization
Author(s) -
Kratochvíl J.,
Sikora A.
Publication year - 2004
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.21255
Subject(s) - crystallization , nucleation , thermodynamics , exponent , kinetic energy , materials science , activation energy , kinetics , crystallography , chemistry , physics , linguistics , philosophy , quantum mechanics
Abstract Nonisothermal crystallization of poly( N ‐methyldodecano‐12‐lactam) (MPA) was investigated using DSC method at cooling rates of 2–40 K/min. With increasing cooling rate, crystallization exotherms decreased in magnitude and shifted toward lower temperatures. Subsequent heating runs (10 K/min) showed an exotherm just above T g , which increased in magnitude with the rate of preceding cooling run, corresponding to the continuation of primary crystallization interrupted as the system crossed T g on cooling. Kinetic evaluation by the Avrami method gave values of exponent n close to 2.0, suggesting two‐dimensional crystal growth combined with heterogeneous nucleation. The Tobin method, covering the intermediate range of relative crystallinities, provided n ≅ 2.20, suggesting possible partial involvement of homogeneous nucleation at later stages of nonisothermal crystallization. The crystallization rate parameter k 1/n showed a linear dependency on cooling rate for both methods, the Tobin values being slightly higher. The Ozawa approach failed to provide reasonable values of the kinetic exponent m of MPA. The Augis–Bennet method was used to determine the effective activation energy of the entire nonisothermal crystallization process of MPA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 564–572, 2005