Disintegrability under composting conditions of plasticized PLA-PHB blends

摘要

The disintegration under composting conditions of films based on poly(lactic acid)-poly(hydrox-ybutyrate) (PLA-PHB) blends and intended for food packaging was studied. TWO different plasticizers, poly(ethylene glycol) (PEG) and acetyl-tri-n-butyl citrate (ATBC), were used to limit the inherent brit-tleness of both biopolymers. Neat PLA, plasticized PLA and PLA-PHB films were processed by melt-blending and compression molding and they were further treated under composting conditions in a laboratory-scale test at 58 ± 2 ℃. Disintegration levels were evaluated by monitoring their weight loss at different times: 0, 7,14, 21 and 28 days. Morphological changes in all formulations were followed by optical and scanning electron microscopy (SEM). The influence of plasticizers on the disintegration of PLA and PLA-PHB blends was studied by evaluating their thermal and nanomechanical properties by ther-mogravimetric analysis (TGA) and the nanoindentation technique, respectively. Meanwhile, structural changes were followed by Fourier transformed infrared spectroscopy (FTIR). The ability of PHB to act as nucleating agent in PLA-PHB blends slowed down the PLA disintegration, while plasticizers speeded it up. The relationship between the mesolactide to lactide forms of PLA was calculated with a Pyrolysis -Gas Chromatography-Mass Spectrometry device (Py-GC/MS), revealing that the mesolactide form increased during composting.