(648f) Simulation of Polymer Crystal Growth with Various Morphologies Using a Phase-Field Model

A
finite element-based phase-field model was developed
to simulate crystal growth in semicrystalline
polymers with various crystal morphologies. The original Kobayashi's
phase-field model for solidification of pure materials was
adopted to account for polymer crystallization. Evolution of a
non-conserved phase-field variable was considered to
track the interface between the melt and the crystalline phases. A local free
energy density was used to account for the meta-stable
states in polymer solidification. The developed model was
successfully applied for simulation of two-dimensional (2D) polymer
single- and polycrystalline morphologies (rectangular, orthorhombic, hexagonal,
and spherulitic) in polypropylene and polystyrene
(example in Fig.1). These morphologies were compared
based on different supercooling and interface
anisotropy. The results of simulated crystal morphology and growth rates were
validated using experiments (example in Fig.2). The unique aspect of this work is that the employed model is
capable of simulating multiple arbitrarily-oriented
crystals and has no limitations with respect to the crystal morphology. The
results show significant thermal effects on the shape and growth rate of polymer
crystals.

Fig.1. 2D representations of a single spherulite growth of isotactic polypropylene crystal.

Fig.2. Optical microscope
(OM) images of spherulites in isotactic polypropylene
at

 (a) 100x and (b) 500x magnifications obtained
with the Carl-Zeiss® inverted OM in DIC mode.