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The Morphology of Blends of Linear and Branched Polyethylenes by Small-Angle Neutron and X-Ray Scattering

Published online by Cambridge University Press:  22 February 2011

J. D. Londono ,
G. D. Wignall ,
R. G. Alamo ,
L. Mandelkern  and
J. S.Lin
J. D. Londono
Affiliation:
Oak Ridge National Laboratory, Oak Ridge TN 37830
G. D. Wignall
Affiliation:
Oak Ridge National Laboratory, Oak Ridge TN 37830
R. G. Alamo
Affiliation:
Oak Ridge National Laboratory, Oak Ridge TN 37830
L. Mandelkern
Affiliation:
Oak Ridge National Laboratory, Oak Ridge TN 37830
J. S.Lin
Affiliation:
Oak Ridge National Laboratory, Oak Ridge TN 37830
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Abstract

The solid-state morphology and liquid-state homogeneity of blends of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) were investigated by small-angle neutron and x-ray scattering (SANS and SAXS). The solid state morphology was investigated as a function of composition and cooling rate from the melt. After slow cooling, the evidence indicated that the mixtures were either completely (HDPE-rich blends) or almost completely (LDPE-rich blends) phase separated into separate HDPE and LDPE lamellae over the whole compositional range. In contrast, for rapidly quenched blends the components are extensively co-crystallized for all concentrations, though the SANS data indicated that the branched component had a tendency to be preferentially located in the inter-lamellar regions. In the liquid state, the blends were homogenous at all compositions, showing that the solid state morphology is not determined by the melt structure, but is a function of the crystallization kinetics. Further evidence for blend homogeneity in the liquid is presented. In particular we examine the hypothesis that a phase separated mixture might give a scattering pattern similar to a homogenous blend if the domain sizes were larger that the maximum spatial resolution of the SANS experiment (D > 2π/Qmin ~ 2000Å). In this scenario, the differential scattering cross section dΣ/dΩ(Q) ~ Q-2, though phase separation decreases the cross section in this Q-range with respect to the homogenous blend. For HDPE/LDPE blends in the melt, this decrease in intensity was not observed, thus ruling out the possibility of phase separation.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 376: Symposium BB – Neutron Scattering in Materials Science , 1994 , 281
Copyright
Copyright © Materials Research Society 1995

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References

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