Structural, mechanical and barrier properties of active PLA-antioxidant films

Ascorbyl palmitate (AP) and alpha-tocopherol (AT) were added to poly-(lactic acid) (PLA) film to investigate their effects on PLA's physical, structural, mechanical and barrier properties. AP crystals appeared on the PLA surface after solvent evaporation and changed PLA transparency. AP decreased the PLA contact angle on the recto side and increased film polarity and wettability. X-ray photoelectron spectroscopy showed that AT increased the concentration of C-(C, H), O=C and O-H bonds on the verso side, but decreased the concentration of C-O and O-CD bonds. Atomic force microscopy confirmed that the PLA surface microstructure was drastically influenced by the addition of antioxidants in terms of roughness parameters (R-a and R-q). AT significantly decreased the film crystallization temperature down to 74.1 degrees C due to its plasticizing effect. Both AT and AP reduced PLA Young's modulus and tensile strength. PLA water vapor permeability was not significantly influenced by AP and AT. AP is not recommended to be used in PLA active packaging. (C) 2012 Elsevier Ltd. All rights reserved.