Role of the interface in the melt-rheology properties of linear low-density polyethylene/low-density polyethylene blends: Effect of the molecular architecture of the dispersed phase

摘要

We studied the melt linear viscoelastic and elongational properties of blends consisting of a Ziegler-Natta linear low-density polyethylene (LLDPE) and different LDPEs. The weight fraction of the LDPE used in the blends was 15%. The linear viscoelastic characterization was performed at different temperatures for all of the blends to determine the thermorheological behavior in the melt state. The blends fulfilled the time-temperature superposition but exhibited a broad linear viscoelastic response, which was further than that expected for miscible blends and even immiscible systems with a sharp interface. A rheological study of the application of the Palierne model revealed that in addition to the droplet shape relaxation, another mechanism was present at lower frequencies. We discuss the results by hypothesizing a strong interaction between the high-molecular-weight linear fraction of the LLDPE matrix and a fraction of molecules of the dispersed phase, which formed a thick interface with its own viscoelastic properties. A clear change in this additional mechanism was observed, depending on the dispersed minor-phase properties, which produced an impact on the processing of the blends, and more precisely, on the values of the melt strength in the melt-spinning experiments. © 2010 Wiley Periodicals, Inc.