Thermorheological properties of LLDPE/LDPE blends |
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Authors: | O Delgadillo-Velázquez S G Hatzikiriakos M Sentmanat |
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Institution: | (1) Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC, Canada;(2) Xpansion Instruments, Tallmadge, OH, USA |
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Abstract: | The thermorheological behavior of a number of linear low-density polyethylene and low-density polyethylene (LLDPE/LDPE) blends
was studied with emphasis on the effects of long chain branching. A Ziegler–Natta, LLDPE (LL3001.32) was blended with four
LDPEs having distinctly different molecular weights. The weight fractions of the LDPEs used in the blends were 1, 5, 10, 20,
50, and 75%. Differential scanning calorimetry (DSC) analysis has shown that all blends exhibited more than one crystal type.
At high LDPE weight fractions, apart from the two distinct peaks of the individual components, a third peak appears which
indicates the existence of a third phase that is created from the co-crystallization of the two components. The linear viscoelastic
characterization was performed, and mastercurves at 150 °C were constructed for all blends to check miscibility. In addition,
Van Gurp Palmen, zero-shear viscosity vs composition, Cole–Cole, and the weighted relaxation spectra plots were constructed
to check the thermorheological behavior of all blends. In general, good agreement is found among these various methods. The
elongational behavior of the blends was studied using a uniaxial extensional rheometer, the SER universal testing platform
from Xpansion Instruments. The blends exhibit strain-hardening behavior at high rates of deformation even at LDPE concentrations
as low as 1%, which suggests the strong effect of branching added by the LDPE component. |
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Keywords: | Activation energy PE Blend Block copolymer Mastercurve Phase separation Polymer blend |
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