M. Agarwal et al., CHARACTERIZATION OF THE DEGRADATION OF POLYLACTIC ACID POLYMER IN A SOLID SUBSTRATE ENVIRONMENT, Biotechnology progress, 14(3), 1998, pp. 517-526
Polylactic acid (PLA) polymer film was degraded in abiotic and biotic
environments to understand the role of microbes in the degradation pro
cess of lactic acid based polymers. The degradation studies were condu
cted in a well-characterized biotic system, an abiotic system, a steri
le aqueous system; and a desiccated environment maintained at 40, 50,
and 60 degrees C. The combination of experiments in different environm
ents isolated the distinct effect of microbes, water, and temperature
on the morphological changes in the polymer during degradation. Due to
lack of availability of radiolabeled PLA, various analytical techniqu
es were applied to observe changes in the rate and/or mechanism of deg
radation. CO2 evolved, weight loss, and molecular weights were measure
d to evaluate the extent of degradation. X-ray diffraction and differe
ntial scanning calorimetry techniques monitored the morphological chan
ges in the polymer. FTIR was used as a semiquantitative tool to gather
information about the chemistry of the degradative process. Neither o
f the above analytical techniques indicated any difference in the rate
or mechanism of degradation attributable to the presence of microorga
nisms. The extent of degradation increased at higher process temperatu
res. FTIR data were evaluated for significant statistical difference b
y t-test hypothesis. The results confirmed hydrolysis of ester linkage
as the primary mechanism of degradation of PLA. On the basis of these
data, a probable path of PLA degradation has been suggested.