Structural transformation of polyethylene phase in oriented polyethylene/polypropylene blends: a hierarchical structure approach

Injection-moulded specimens of polyethylene/polypropylene blends were drawn at room temperature and subsequently annealed at 140°C, i.e. above the melting temperature of polyethylene, but below the melting temperature of isotactic polypropylene. Structural transformations of the polyethylene phase were assessed at several levels of hierarchical structure by polarised FTIR spectroscopy with photoacoustic detection, DSC, WAXS and SAXS analyses, and dynamic mechanical analysis. The results indicate reorientation of polyethylene chains, corresponding rearrangement of crystalline lamellae and healing of interfibrillar flaws upon annealing.