Ageing effect on morphology, thermal and mechanical properties of impact modified LDPE/PP blends from virgin and recycled materials

An experimental study was conducted to investigate the influence of ageing on the morphological, thermal and mechanical properties of virgin and two types of recycled (from technological and postconsumer wastes) modified polyolefin blends. Immiscible blends of virgin low-density polyethylene (LDPE) and polypropylene (PP) in weight ratio 1:1 were modified with the ethylene–propylene diene monomer (EPDM) rubber impact modifier. The efficiency of modification was investigated as a function of modifier content in the range from 7 to 15 wt%. The blends were prepared by extrusion using a corotating twin screw extruder Brabender DSE35/17D at melt temperature in the range from 150 to 200°C and a screw speed of 20 rpm. Compression-molded samples were subjected to natural and accelerated ageing and characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and mechanical testing. The experiments show that the ageing process deteriorates the mechanical properties of the PP/LDPE blends, and this is more clearly expressed in the blends of virgin material. The results show that the presence of the EPDM modifier delays the process of ageing in PP/LDPE blends. The DSC and SEM investigations confirm the structural changes in the examined compositions.