ABSTRACT
Chitosan (CS) layers are coated on a poly(ethylene terephthalate) (PET) film in order to decrease the oxygen permeability through the polymeric films for food packaging applications. Oxygen transmission rate (OTR) of the 130 µm PET films can be decreased from 11 to only 0.31 cm3/m².day with a coated layer of 2 µm of CS. Additional decrease is obtained with the addition of vermiculite (VMT) to CS matrix in high proportion (40 to 50 w/w%). The OTR of the coated PET films decreased to very low values, below the detection limit of commercial instrumentation (≤0.008 cm3/m2 day). This high-barrier behavior is believed to be due to the brick wall nanostructure, which produces an extremely tortuous path for oxygen molecules.
ABSTRACT
In this study, a novel and extremely facile method for the synthesis of conducting polypyrrole (PPy) was achieved in aqueous solution. This radiolytic method is totally free of template and environmentally friendly compared with traditional chemical methods. According to ultraviolet-visible (UV-vis) spectroscopy and Fourier transform infrared (FTIR) spectroscopy analysis, pyrrole (Py) monomers were polymerized into PPy thanks to their oxidation by HO(â¢) radicals produced by the radiolysis of water when exposed to γ irradiation. The morphology of PPy was characterized by cryo-transmission electron microscopy (cryo-TEM) in aqueous solution and by scanning electron microscopy (SEM) after deposition. In an original way, high-resolution atomic force microscopy, coupled with infrared nanospectroscopy, was used to probe the local chemical composition of PPy nanostructures. The results demonstrated that spherical and chaplet-like PPy nanostructures were formed by γ-radiolysis. Thermogravimetric analysis (TGA) and electronic conductivity measurements showed that radiosynthesized PPy had good thermal stability and an electrical conductivity higher than that of chemically synthesized PPy.
