Orientation induced brittle – Ductile transition in a polyethylene/polyamide 6 blend

Polyamide/polyolefin blends are of scientific and technological interest but, on the other hand, the different chemical nature of the two components makes them incompatible, resulting in unsatisfactory physical properties and making compatibilization necessary. In particular, although the two components are ductile, the binary blends can show brittle behaviour. It is also known that the effect of the elongational flow (and then of the induced orientation) on polymer blends is a decrease of elongation at break with increase of the degree of orientation. In this work, the effect of orientation on the mechanical properties of a low density polyethylene/polyamide 6 incompatible blend was investigated. An unexpected, orientation-induced brittle/ductile transition has been found, and interpreted in terms of microstructural changes, involving the orientation of the matrix macromolecules and of the dispersed phase particles.