Miscibility of hexene-LLDPE and LDPE blends: influence of branch content and composition distribution

The influences of branch content (BC) and composition distribution (CD) of hexene linear low-density polyethylene (LLDPE) on its miscibility with low-density polyethylene (LDPE) were investigated. Ziegler–Natta (ZN) and metallocene-LLDPE (m-LLDPE) were used to study the melt miscibility using rheological tools. Dynamic, steady shear and transient measurements were carried out in an ARES rheometer at 190 °C. The miscibility was revealed by the dependence of their ηo, η′(ω), G′, and N1(γ̇) on blend composition. The CD of LLDPE has influenced its miscibility with LDPE. The ZN–LLDPE blend with LDPE was found to be more miscible than an m-LLDPE of the same Mw and similar BC. On the other hand, a high-BC m-LLDPE (32.2 CH3/1000 C) was found to be more miscible with LDPE than a low-BC m-LLDPE (14.4 CH3/1000 C) of the same Mw and MWD. The high-BC m-LLDPE blends with LDPE were partially miscible and immiscibility is likely to develop in LDPE-rich blends. Agreement was observed between the measured rheology and theoretical predictions of Einstein, Scholz et al., Palierne, and Bousmina emulsion models.