Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Methodology for identifying multilayer packaging materials using selective dissolution and precipitation technique, microscopy, FTIR, and DSC.

ABSTRACT
Environmental problems related to waste accumulation have encouraged recycling, especially of polymers, such as multilayer packaging, which is hardly recycled because it consists of distinct materials in each layer. Furthermore, knowing the polymers that compose the films is essential to make their recycling feasible. The purpose of this work was to identify the polymers that compose three different post-consumer multilayer packaging films by the techniques of selective dissolution and precipitation in a system of solvent-nonsolvent composed of toluene-acetone, Fourier transformed infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Selective dissolution suggested the presence of 1.5–11 wt% of ethylene vinyl alcohol copolymer (EVOH), polyamide (PA), poly(ethylene terephthalate) (PET), and/or poly(vinyl chloride) (PVC), and 77–93.5 wt% of ethylene vinyl acetate copolymer (EVA), polyethylene (PE), and/or polypropylene (PP) in the packaging films. FTIR spectra showed characteristic absorption bands of EVA, EVOH, PE, PET, and PA, whereas DSC curves indicated the presence of high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), modified PE, EVOH, and PA, which were assumed to be the constituents of the films. These results proved that the techniques selected to analyze the films were suitable and produced valuable information for the recycling of these materials.