Co-crystallization in ternary polyethylene blends: tie crystal formation and mechanical properties improvement

Understanding the co-crystallization behavior of ternary polyethylene (PE) blends is a challenging task. Herein, in addition to co-crystallization behavior, the rheological and mechanical properties of melt compounded high density polyethylene (HDPE)/low density polyethylene (LDPE)/Zeigler-Natta linear low density polyethylene (ZN-LLDPE) blends have been studied in detail. The HDPE content of the blends was kept constant at 40wt% and the LDPE/ZN-LLDPE ratio was varied from 0.5 to 2. Rheological measurements confirmed the melt miscibility of the entire blends. Study of the crystalline structure of the blends using DSC, wide angle X-ray scattering, small angle X-ray scattering and field emission SEM techniques revealed the formation of two distinct co-crystals in the blends. Fine LDPE/ZN-LLDPE co-crystals, named tie crystals, dispersed within the amorphous gallery between the coarse HDPE/ZN-LLDPE co-crystals were characterized for the first time in this study. It is shown that the tie crystals strengthen the amorphous gallery and play a major role in the mechanical performance of the blend.(c) 2016 Society of Chemical Industry