Blown Film Characterization of Binary Blends of Metallocene-Catalyzed LLDPEs

摘要

We have explored the effects of blending metallocene-catalyzed linear low-density polyethylenes (LLDPE) of reasonably differing molecular weights on the performance and orientation characteristics of blown films. The presence of relatively longer molecules in a metallocene-catalyzed LLDPE re- sulted in blown films with relatively lower machine direction (MD) tear resis- tance, lower impact strength and higher transverse direction (TD) tear resis- tance. While all of the blown films investigated displayed the Keller-Machin "row" structure, the degree of orientation was observed to increase with in- creasing concentration of long molecules (or high molecular weight blend com- ponent). The observed influence of orientation in the crystalline and non-crystalline phases on the Elmendorftear resistance of the blown films was observed to be consistent with previous investigations on a wide spectrum of commercial LLDPE blown films [15]. Morphological investigations of the blend films indicated the potential significance of microstructural anisotropy on blown film impact performance. This calls into question the wide-spread notion that co-monomer distribution profile is largely responsible for distinguishing the impact performance of various classes of LLDPE blown films.