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Crystallization behavior and spherulitic morphology of poly(lactic acid) films induced by casting process
Author(s) -
Houichi Hikmet,
Maazouz Abderrahim,
Elleuch Boubaker
Publication year - 2015
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.24028
Subject(s) - crystallization , materials science , nucleation , morphology (biology) , casting , kinetics , isothermal process , chemical engineering , optical microscope , growth rate , avrami equation , composite material , thermodynamics , crystallization of polymers , scanning electron microscope , polymer , physics , geometry , mathematics , quantum mechanics , biology , engineering , genetics
A novel way using a polarized optical microscopy and statistical image analysis techniques for direct investigation of the crystallization kinetics and spherulitic morphology of poly (lactic acid) induced by casting process has been proposed. DSC analyses were carried out to explore the effect of drawing in thermal properties of PLA. We found that the rate of cold crystallization was sharply increased with draw ratio. Isothermal calorimetric results reveal that thin films crystallize slowly compared to sheets. Moreover, thin films don't fit the Avrami model demonstrating that more stretching may modify the crystallization kinetics of films. A comparison was made between pure PLA and stretched materials using Hoffman theory and giving a compiled view on the details of crystallization behavior with relation to stretch effect. At draw ratio 167, the growth rate reach its maximum and the crystallization rate go up exponentially. POM experiments showed the existence of two different spherulitic populations in thin films and two nucleation mechanisms was identified. Accordingly, the growth rate was found to be not linear with time. Furthermore, the X‐ray diffraction analyses showed the presence of α and α ' crystal form in thin films contrarily to sheets with α form. POLYM. ENG. SCI., 55:1881–1888, 2015. © 2014 Society of Plastics Engineers