Melt miscibility and mechanical properties of metallocene LLDPE blends with HDPE: Influence of Mw of LLDPE

Abstract

The influence of Mw of LLDPE on the rheological, thermal and mechanical properties of m-LLDPE/HDPE blends of low and high branch content (BC) was studied. Melt rheology of m-LLDPE blended with linear HDPE revealed strong influence of Mw on melt miscibility at both branching levels. Low Mw m-LLDPE/HDPE blends are suggested to be miscible at all compositions, while viscosity of high Mw m-LLDPE/HDPE blends showed negative deviation from log additivity suggesting layered morphology of these blends. The DSC results suggest that compatibility in the solid state is independent of Mw and BC. For all blends studied, the HDPE-rich blends were found to contain single crystal populations suggesting high degree of cocrystallization, whereas, m-LLDPE rich phase showed separate crystallization. The melt miscibility and the crystallization of high BC m-LLDPE blends with HDPE are suggested to be controlled by different factors. Small strain mechanical properties of these blends were found to be a strong function of blend compatibility and the specific properties of the blend components. © 2006 The Society of Polymer Science.