Linear low-density polyethylene/poly(ethylene-ran-butene) elastomer blends: Miscibility and crystallization behavior

Abstract

The phase and crystallization behavior of the blends consisting of LLDPE (0.7 mol% hexene copolymer) and PEB (26 mol% butene copolymer) have been investigated using optical microscopy (OM), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The blends exhibited an upper critical solution temperature of 162°C. The solubility parameter analysis showed that the solubility parameter of LLDPE decreased more rapidly than that of PEB with temperature. However, due to the slow kinetics of phase separation, at lower crystallization temperatures, the crystallization and melting behavior of LLDPE mainly reflected the miscibility between LLDPE and PEB. Crystallization from the two-phase state could present two crystallization peaks. PEB didn’t change the crystal cell unit and crystallinity of LLDPE, but changed its distribution of lamellar thickness or crystal perfection. The dilute effect of PEB also changed the overall nature of the nucleation and growth process of LLDPE. The equilibrium melting temperature in this blend could be obtained by the Hoffman-Weeks method, and comparing with that of the pure LLDPE, it was reduced and kept relatively constant in the bi-phase state. The phase diagram made up of the LLPS boundary, equilibrium melting temperatures and melting temperatures observed may be better to indicate the phase and crystallization behavior of LLDPE/PEB blends.