Elongational rheology of LLDPE / LDPE blends

The objective of this study is to investigate the effect of low density polyethylene (LDPE) content in linear low density polyethylene (LLDPE) on the crystallinity and strain hardening of LDPE / LLDPE blends. Three different linear low density polyethylenes (LL-1, LL-2 and LL-3) and low density polyethylenes (LD-1, LD-2 and LD-3) were investigated. Eight blends of LL-1 with 10, 20, 30 and 70 wt % of LD-1 and LD-3, respectively, were prepared using a single screw extruder. The elongational behavior of the blends and their constituents were measured at 150°C using an RME rheometer. For the blends of LL-1 with LD-1, the low shear rate viscosity indicated a synergistic effect over the whole range of concentrations, whereas for the blends of LL-1 with LD-3, a different behavior was observed. For the elongational viscosity behavior, no significant differences were observed for the strain hardening of the 10–30% LDPE blends. Thermal analysis indicated that at concentrations up to 20%, LDPE does not significantly affect the melting and crystallization temperatures of LLDPE blends. In conclusion, the crystallinity and rheological results indicate that 10–20% LDPE is sufficient to provide improved strain hardening in LLDPE. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3070–3077, 2003