Compatibilization of polyethylene (waste) mixtures through reactive extrusion

Abstract

The production of plastic materials has experienced incredible growth over the past decades. Polyethylene constitutes the largest part (25%) of plastic production, finding its application mostly as film in industrial and food packaging and agricultural use. However, since packaging materials are getting increasingly complex, polyethylene waste is nearly always mixed with other polymers, making direct recycling impossible. Compatibilization of polymer blends can be used to convert an immiscible polymer blend into a homogeneous material with synergistic properties. When this compatibilization is carried out inside an extruder, one less reaction step is needed and the material can directly be processed according to its application.

This study addresses the reactive compatibilization of recycled LDPE (rLDPE) originating from industrial film waste with its polymer impurities, as well as virgin low-density polyethylene (LDPE)/polyamide 6 (PA6) blends of various compositions through reactive extrusion with PE grafted with MA (PE-g-MA). A literature review was carried out, summarising the current state-of-the-art of reactive compatibilization and reactive extrusion. The composition of the recycled stream was identified through various characterisation methods. Through a wide variety of characterisation techniques, the mechanical properties of the extruded sample pellets were investigated, as well as the mechanical and optical properties of the blown film.

The compatibilizing effect on the virgin LDPE/PA6 blends was found to grow in importance with increasing PA6 content. For 1 wt%, the samples did not exhibit any improvement upon compatibilization. The samples containing 5 wt% showed their improvements predominantly in the optical properties. The 10 wt% samples showed large enhancements overall, after being treated with the compatibilizer. Both the optical and mechanical properties of rLDPE saw a significant amelioration as a result of compatibilization. This study thus achieved compatibilization through reactive extrusion for an extensive variety of polymer samples.