The morphology of blends of linear and branched polyethylenes by small-angle neutron and x-ray scattering

Book · Sun Dec 31 04:00:00 EST 1995

OSTI ID:225269

Londono, J D; Wignall, G D; Lin, J S ^[1]; Alamo, R G; Mandelkern, L ^[2]

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1. Oak Ridge National Lab., TN (United States)
2. Florida State Univ., Tallahassee, FL (United States)

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 homogeneous 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 the authors examine the hypothesis that a phase separated mixture might give a scattering pattern similar to a homogeneous blend if the domain sizes were larger than the maximum spatial resolution of the SANS experiment (D > 2{pi}/Q{sub min} {approximately} 2,000 {angstrom}). In this scenario, the differential scattering cross section d{Sigma}/d{Omega}(Q) {approximately} Q{sup {minus}2}, though phase separation decreases the cross section in this Q-range with respect to the homogeneous blend. For HDPE/LDPE blends in the melt, this decrease in intensity was not observed, thus ruling out the possibility of phase separation.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 225269
• Report Number(s): CONF-941144--; ISBN 1-55899-278-2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
DIAGNOSTIC TECHNIQUES
EXPERIMENTAL DATA
MORPHOLOGY
NEUTRONS
PHASE STUDIES
POLYETHYLENES
SMALL ANGLE SCATTERING
SOLUBILITY
X RADIATION