1 research outputs found
Biological Oxidative Mechanisms for Degradation of Poly(lactic acid) Blended with Thermoplastic Starch
In
the present study, polyÂ(lactic acid) (PLA) and their blends
with 5%/wt and 10%/wt thermoplastic starch (TPS) were submitted to
degradation in simulated soil. To investigate the mechanisms involved
in the degradation, we also submitted the samples to degradation by <i>tert</i>-butyl hydroperoxide, myoglobin, and peroxide-activated
myoglobin. The samples were analyzed by Fourier-transformed infrared
spectrometry (FTIR), scanning electronic microscopy (SEM), contact
angle analysis, and mass loss measurement. The FTIR results indicated
a weak interaction between the two components (PLA and starch) in
the blend’s amorphous structure. However, the corresponding
SEM images showed that TPA increased ridges and roughness at the material
surface associated with an increase of wettability evidenced by contact
angle analysis. Consistently, TPS favored degradation of the material
both in the simulated soil and pro-oxidant model systems. In the simulated
soil, the occurrence of TPS hydrolysis provided glucose, a biological
fuel, that contributed to the growth of the microorganisms. The similar
degradation patterns observed in mimetic pro-oxidant biological systems
and soil suggest that oxidative reactions catalyzed by heme proteins
from biological sources as well as the presence of peroxides and transition
metal traces in the original materials have a significant contribution
to PLA and PLA/TPS degradation