Effects of reprocessing cycles and ageing on the rheological and mechanical properties of virgin-recycled HDPE blends

Laboratoire des Systèmes Electromécaniques (LASEM), Ecole Nationale d’Ingénieurs de Sfax (ENIS), Université de Sfax, B.P.W3038, Sfax, Tunisie
mnif.ridha@yahoo.fr

Received: 10 June 2015
Accepted: 4 November 2015

Abstract

The reprocessing ability of virgin and recycled High Density Polyethylene (HDPE) blends has been investigated to examine the recycling feasibility in industrial production. Virgin-recycled HDPE blends were re-processed and re-formed up to three cycles by extrusion moulding. The effect of recycled HDPE content and reprocessing cycles coupled with ageing through “transyl” on the properties of the prepared blends was evaluated by tensile test and by melt flow index (MFI) tests. Furthermore, the ageing of the blends were studied via an immersion in “transyl” lubricant (Hydrocarbons, C10-C13, N-Alkanes, Isoalckanes, Cyclics, Aromatics (2–25%)). The sorption process was analyzed by gravimetric measurements at different temperatures. Also, diffusion coefficients of solvent molecules in the HDPE samples were identified. Results revealed that the mechanical properties of the samples worsened on increasing the level of recycled HDPE and after each reprocessing operation even if the most relevant decreases were observed after the first reprocessing. The processability of virgin-recycled HDPE blends has lead to slight decrease of viscosity, more remarkable on increasing the recycled HDPE content. The rheological behaviour was not influenced by the reprocessing only at the first three reprocessing cycles. The combination of reprocessing and accelerated ageing has degraded the material faster than either processing or ageing performed separately.