1. Introduction
Poly(lactic acid) (PLA) is a well-known biodegradable and biocompatible
polyester derived from renewable resources like corn. Over the
past decade, the discovery of newpolymerization routes alongwith the
elevated environmental awareness of the general public, has resulted
in an expanded use of PLA in the form of fibers and films [1–3]. The
extrusion cast PLA films are usually amorphous, due to its intrinsic slow
crystallization rate [4–6]. Amorphous PLA has lower strength and
dimensional stability, requiring stretching and/or annealing above its
glass transition temperature in order to increase molecular orientation
and crystallinity for many commercial applications. Several research
groups have investigated the evolution of orientation and crystalline
structure during uniaxial deformation of PLA in the rubbery state from
the amorphous precursors [4,7–9]. The structural evolution during
biaxial stretching and subsequent annealing of PLA cast films has also
been presented [10–12]. However, less attention has been paid on the
annealing behavior of as-cast PLA films. Yu et al. [5] reported some data
on PLA extrusion cast films, however, only one-dimensional wide angle
X-ray diffraction (WAXD) results were shown.