Phase behavior of blends of linear and branched polyethylenes in the molten and solid states by small-angle neutron scattering
- Florida State Univ., Tallahassee, FL (United States). Dept. of Chemistry
- Oak Ridge National Lab., TN (United States)
- Exxon Chemical Co., Baytown, TX (United States). Plastics Technology Division
The state of mixing in blends of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) in the liquid and solid state has been examined by small-angle neutron scattering (SANS) in conjunction with deuterium labeling. In the melt, SANS results indicate that HDPE/LDPE mixtures from a single-phase solution for all concentrations, including blends containing high volume fractions ([phi] > 0.5) of branched polymer, for which multiphase melts have previously been suggested. Proper accounting for isotope effects is essential to avoid artifacts, because the H/D interaction parameter is sufficiently large ([sub [chi]HD] [approximately] 4 [times] 10[sup [minus]4]) to cause phase separation in the amorphous state for molecular weights (MW) >150,000. In the solid state, after slow cooling from the melt ([approximately]0.75 C/min), the HDPE/LDPE system shows extensive segregation into separate domains [approximately]100--300 [angstrom] in size. Both the shape and magnitude of the absolute scattering cross section are consistent with the conclusion that the components are extensively segregated into separate lamellae. Two-peak melting curves obtained for such mixtures support the SANS interpretation, and the segregation of components in the solid state is therefore a consequence of crystallization mechanisms rather than incompatibility in the liquid state.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5090665
- Journal Information:
- Macromolecules; (United States), Vol. 27:2; ISSN 0024-9297
- Country of Publication:
- United States
- Language:
- English
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