Rotational Molding of Recycled HDPE

A significant fraction of the polymeric wastes consists of high density polyethylene for blow molding typically recycled in injection molding and extrusion processes but very often wasted. On the other hand, the polyethylene grades used in Rotational Molding technique are much less available as recycled polymers. In this work the rotational molding of blends of virgin LLDPE (rotational molding grade) and recycled High Density PE (r-HDPE), coming from urban wastes, has been studied. As a first approach r-HDPE and virgin LLDPE have been extrusion blended. Rheological and mechanical properties of different mixtures have been evaluated and compared with those of the virgin LLDPE. The very high viscosity of LLDPE/r-HDPE, not suitable for rotational molding, suggested a direct mixing of powders of r-HDPE and LLDPE at the loading stage of the rotational molding process. The morphology and mechanical properties of a rotational molded part, obtained in this way, have been compared with those the extrusion blended samples. In particular, a composite like morphology led to improved strength and stiffness.