Reactive compatibilization and melt compounding with nanosilicates of post-consumer flexible plastic packagings

Flexible plastic packagings are rapidly gaining market share since they offer significant functional benefits. However, they also pose a challenge from a recycling perspective. In fact, due to the presence of different polymeric fractions and to contamination by organic substances and out-of-target materials, such as paper and metals, the mechanical properties of the recycled material are relatively poor. Addition of nanoparticles to plastic waste can offer the combinations of improved properties and processing, and reduce operational cost. Moreover, in recent studies it was demonstrated that they can also act as blend compatibilizers. The aim of this study is the upgrading of Fil-s (acronym for film-small), a fraction of mixed plastic waste stream obtained by the separation and mechanical recycling of post-consumer packaging films of small size. Physical, chemical and rheological characterization evidenced that Fil-s stream is mainly composed of polyethylene and a smaller fraction of polypropylene. With the purpose to improve the performances of Fil-s, lamellar and acicular organoclays were melt compounded with the recycled material in a twin-screw extruder. Moreover, in order to enhance the compatibility between the polyolefin components and the nanofiller dispersion in the mixed polymer matrix, the functionalization of Fil-s with maleic anhydride (MAH) was realized by reactive extrusion. Morphological, thermal, rheological and mechanical properties of the functionalized materials and the nanocomposite systems were extensively discussed. The positive effect of the MAH-grafting on the compatibilization between the two polyolefin components of Fil-s was pointed out and an interesting improvement in ductility of Fil-s was obtained. The further addition of the nanoclays also significantly increased the stiffness of the systems.