Rheological study of heterogeneities in melt blends of ZN-LLDPE and LDPE: Influence of Mw and comonomer type, and implications for miscibility

It is estimated that 60 to 70% of LLDPE enters the market as blends (Utracki 1989a), primarily with other members of the polyolefin family, e.g., LDPE or polypropylene (PP). Despite the long history of polyethylene (PE) blending and its widespread use, many questions about the homogeneity of such blends, with obvious implications for thermodynamics and for the rheology, are still not answered to everyone’s satisfaction. Here we employ rheology to address specifically one of the most common types of blends, namely those using LLDPE and LDPE, where Ziegler-Natta (ZN) LLDPE is used. Even within this type of blend, there can be enormous variations due to volume fraction, u, molecular weight, choice of LLDPE comonomer (i.e., branch length) and branch content as well as distributions of both molecular weight and branching along the LLDPE main chain. For polyethylenes the simple study of the phase morphology of the melt tends to be unhelpful, and in Ibnelwaleed A. Hussein Michael C. Williams Rheological study of heterogeneities in melt blends of ZN-LLDPE and LDPE: Influence of Mw and comonomer type, and implications for miscibility