Rheological study of the influence of Mw and comonomer type on the miscibility of m-LLDPE and LDPE blends

The influences of molecular weight and m-LLDPE comonomer type on the miscibility of m-LLDPE with LDPE in the melt state were investigated with rheological methods. Dynamic, steady shear and transient measurements were carried out in an ARES rheometer at 190 °C. The Mw of the shortly branched m-LLDPE has influenced its miscibility with LDPE and immiscibility has increased with the increase in Mw of m-LLDPE. The miscibility of the high-Mw m-LLDPE with LDPE was non-symmetric with respect to composition as revealed by the dependence of their η0, η′(ω), G′, N1(γ̇), and N1(t) on blend composition. Addition of a small amount of the hexene m-LLDPE to LDPE was more likely to cause immiscibility than the addition of a small amount of LDPE to m-LLDPE. Increasing the m-LLDPE branch length (comonomer) from butene to hexene did not influence the miscibility of m-LLDPE/LDPE blends. Agreement was observed between the measured rheology and theoretical predictions of Einstein, Scholz et al., Palierne and Bousmina emulsion models. The ratio of interfacial tension to droplet radius was estimated to be ∼103 N/m2.