Effect of various alumina nano‐fillers on the thermal and mechanical behaviour of low‐density polyethylene–Al₂O₃ composites

Two different alumina powders were dispersed in low‐density polyethylene (LDPE) to evaluate if any role can be ascribed to the crystalline phase, size and morphology of the alumina filler. In particular a submicrometric α‐alumina and a nanocrystalline transition (γ/δ) alumina were added to the polymer at 5 wt% concentration, using a Brabender mixing unit. Both the neat inorganic fillers showed a good dispersibility in the polyolefin. The thermal and mechanical properties of the composites obtained were evaluated. As expected, a significant increase of the stiffness and abrasion resistance of LDPE was achieved in both cases. Furthermore, the composites showed a higher thermo‐oxidative stability with respect to neat LDPE. Independent of their crystalline phase, size and morphology, both fillers gave a similar enhancement of composite features.