Nanostructured Composites Based on Polyethylene–Polyamide Blends. I. Preparation and Mechanical Behavior

Abstract

The objective of this study is to manufacture and investigate novel microfibrillar‐reinforced materials (MFC) based on oriented blends of high‐density polyethylene (PE) and polyamide 12 (PA12). Compositions containing 10 and 20 wt% of PA12 were prepared, some of the latter comprising also 10 wt% of a copolymeric compatibilizing agent. The blends were extruded in the form of strands subsequently cold drawn to reach a maximum draw ratio of λ≈16. The oriented strands so produced were further compression molded at 155°C, thus, obtaining film‐shaped MFC in which the PE isotropic matrix was reinforced by long PA12 microfibrils with a preferred orientation or by short, randomly oriented PA12 microfibrils. The PE–PA12 films also were pressed with no orientation of either phase. The PE–PA12‐based MFC were characterized by microscopy techniques, thereby, proving the existence of the reinforcing microfibrils. Differential scanning calorimetry studies provided indications for chemical interactions induced by the compatibilizer. The MFCs based on the compatibilized PE:PA12 displayed stress at break values being 50–60% higher than those of the matrix material (PE). This effect was accompanied by disappearing of the cold flow region in the stress–strain curve. The mechanical and structural data of all MFCs were discussed in respect to the polyamide fibrils length and orientation, as well as to the effect of compatibilizer.