Uniaxial elongational flow effects and morphology development in LDPE/phosphate glass hybrids |
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Authors: | Kevin Urman Thomas Schweizer Joshua U Otaigbe |
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Institution: | (1) School of Polymers and High Performance Materials, The University of Southern Mississippi, 118 College Drive #10076, Hattiesburg, MS, USA;(2) Department of Materials, Polymer Physics, ETH Zürich, 8093 Zürich, Switzerland |
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Abstract: | Shear and elongational viscosity measurements were performed on low-density polyethylene/phosphate glass (LDPE/Pglass) hybrid
materials in the liquid state. Under shear deformation, the hybrids with low concentrations of Pglass showed a Newtonian region
at low frequencies, followed by shear-thinning behavior at high frequencies. High Pglass concentrations displayed shear-thinning
behavior over the whole range of frequencies studied. Deviations from the log-additivity rule for viscosity were found to
be compositionally dependent and generally indicated an immiscible mixture. The elongational viscosity of the hybrids increased
at very low Pglass concentrations (1–2 vol.% Pglass) and then was drastically reduced at higher concentrations (i.e., >10 vol.%
Pglass). In addition, elongational flow was found to induce the formation of Pglass fibrils in hybrids containing at least
10 vol.% Pglass. This was correlated to the elongational capillary number; the critical elongational capillary number was
estimated to be 0.22. The elongational deformation was also found to greatly increase the overall crystallinity of the system
due to molecular orientation of the LDPE polymer chains as confirmed by wide angle X-ray diffraction. A critical composition
of 5 vol.% Pglass was found to be the point at which LDPE hybrid rheological properties, molecular orientation, and morphology
changed drastically. |
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Keywords: | Extensional rheology Phosphate glass/polymer hybrids Morphology Flow induced orientation Crystallization |
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