Upgrading of recycled plastics obtained from flexible packaging waste by adding nanosilicates

Currently, the growing consumption of polymer products creates large quantities of waste materials resulting in public concern in the environment and people life. The efficient treatment of polymer wastes is still a difficult challenge and the recycling process represents the best way to manage them. Recently, many researchers have tried to develop nanotechnology for polymer recycling. The products prepared through the addition of nanoparticles to post-used plastics could offer the combination of improved properties, low weight, easy of processing and low cost which is not easily and concurrently found by other methods of plastic recycling. In this study materials, obtained by the separation and mechanical recycling of post-consumer packaging films of small size (<A3, that is <297×420 mm×mm) were provided by COREPLA. The physical, chemical and rheological characterization of these recycled plastics (denoted as Recyclate A and Recyclate B) evidenced that they are mainly constituted of polyethylene (PE) and of a small fraction of polypropylene (PP). PE/PP incompatibility has been proved and explained in many studies reported in the literature and it represents the main reason for the unsatisfactory mechanical properties of these recycled plastics. The aim of this work was to improve the mechanical properties of these recycled polymeric mixtures by the addition of two different types of organo-modified silicates, also taking advantage of the function of nanofillers as potential blend compatibilizers. In particular, three organoclays (Dellite 67G, sepiolite PM15 and sepiolite UNISA1), differing for the morphology (lamellar or acicular) and/or the type of organic modifier, were melt compounded with the recycled materials in a twin-screw extruder. The morphological, thermal, rheological and mechanical properties of the prepared nanocomposites were extensively discussed.