Miscibility analysis in LLDPE/LDPE blends via thermorheological analysis: Correlation with branching structure

Abstract

This article describes correlation between thermorheological properties and the miscibility of LLDPE/LDPE blends. Samples of LLDPE/LDPE with the blending ratio of 5/95, 10/90, 25/75, 50/50, 75/25, and 90/10 were prepared via melt mixing in a twin screw extruder. Both applied polyethylenes are varying in their long‐chain branches. Five methods including the time–temperature superposition (TTS) principle, van Gurp–Palmen plot, Cole–Cole curve, zero‐shear viscosity as a function of concentration, and relaxation spectrum were employed to examine the miscibility behavior of the samples. The results obtained by these methods indicated the immiscibility of the LLDPE/LDPE blends except the one with 10 wt% LLDPE content. Moreover, Scholz and Einstein models used for further checking of miscibility of the blends showed consistent results. Also, by using the Scholz model, the value of α/ R , ratio of interfacial tension to droplet radius, for the blend with 95 wt% LLDPE content was estimated as 876 N m −2 that was comparable with prior values found for LLDPE/LDPE blends. The potential of thermorheological approach as an alternative powerful tool for analyzing LCB and miscibility issues in PE blends could be highlighted. POLYM. ENG. SCI., 54:1081–1088, 2014. © 2013 Society of Plastics Engineers