Both surface and bulk erosion mechanisms have been argued for
PLA hydrolytic degradation in literature [12,14,30]. Luo et al. have
found that adding TiO2 nanoparticles can change the hydrolytic
mechanism from heterogenous degradation for unfilled PLA to bulk
degradation, which is in correlation with the hydrophilicity of TiO2
nanoparticles [30]. In our study, however, we have found that the
bulk erosion dominates not only in PLA but also in PLA/NR blends
even though a quickly erosion occurred on the surface just like
shown in the surface analysis. This indicates that NR does not
change the erosion mechanism of PLA though NR has enhanced the
hydrophobility of PLA, which will be further confirmed by the
following investigation