Amorphous and crystallized poly(L-lactic
acid) (PLLA) films were prepared and the hydrolytic
degradation of the ultraviolet (UV)-treated and UV-nontreated
films was investigated. This study reveals that
the combination of UV and thermal treatments can produce
the PLLA materials having different hydrolytic
degradation profiles and that the UV-irradiation in the
environment will affect the design of recycling process
for PLLA articles. In an early stage, the degrees of
hydrolytic degradation monitored by weight loss (Wloss),
number-average molecular weight (Mn), and melting
temperature (Tm) were higher for the UV-treated films
than for the UV-nontreated films. In a late stage, the
trend traced by Wloss was reversed, and the difference
in the degrees of hydrolytic degradation between the
UV-treated and UV-nontreated films monitored by Mn
and Tm became smaller, with the exception of the
degrees of hydrolytic degradation of the amorphous
films traced by Tm. Also, in the early stage, the degrees
of hydrolytic degradation monitored by Wloss and Mn
were higher for the crystallized films than for the amorphous
films. In the late stage, this trend was reversed,
with the exception of the degrees of hydrolytic degradation
of the UV-treated films monitored by Mn. The main
factors that determined the Wloss and Tm were the molecular
weight and initial crystallinty but not the molecular
structures such as terminal C¼C double bonds and
crosslinks. VC 2012 Wiley Periodicals, Inc. J Appl Polym
Sci 125: 2394–2406, 2012