High-temperature flow behavior of glass-forming liquids

A free-volume interpretation

M. Cukierman, J. W. Lane, Donald R Uhlmann

Research output: Contribution to journalArticle

119 Citations (Scopus)

Abstract

High-temperature viscous flow data are reported for three relatively simple organic liquids: o-terphenyl, salol, and α-phenyl-o-cresol. The results are combined with previous flow data on the same liquids to obtain viscosity-temperature relations over some 15 orders of magnitude. For each liquid, as well as for tri-α-naphthylbenzene, the free-volume theory of Turnbull and Cohen is found to provide a close representation of the data for viscosities between 10-2 P (the high-temperature limit of the data) and about 104 P. Over this range, even the pre-exponential factors derived from fitting the experimental results are in close agreement with those predicted by the theory. At lower temperatures, the free-volume expression overestimates the difficulty of flow. For all four organic liquids, the fractional free volumes at the points of departure, T, of the experimental data from the free volume predictions are close to 0.015. An empirical high-temperature flow relation of the free-volume form is suggested as η≈s[(MkT)1/2/a20] exp{0.25/[0.015 + Δα(T - TB)]}, where M is the mass of the molecule, a 0 is its diameter, and Δα is the difference in thermal expansion coefficient between liquid and glass. It is suggested again that free-volume theories be used to represent flow behavior in the fluid range rather than in the high-viscosity region as the glass transition is approached.

Original languageEnglish (US)
Pages (from-to)3639-3644
Number of pages6
JournalThe Journal of Chemical Physics
StatePublished - 1973
Externally publishedYes

Fingerprint

Free volume
Glass
glass
Liquids
liquids
organic liquids
Viscosity
viscosity
Temperature
cresols
terphenyls
viscous flow
Viscous flow
Thermal expansion
Glass transition
thermal expansion
Molecules
Fluids
fluids
coefficients

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

High-temperature flow behavior of glass-forming liquids : A free-volume interpretation. / Cukierman, M.; Lane, J. W.; Uhlmann, Donald R.

In: The Journal of Chemical Physics, 1973, p. 3639-3644.

Research output: Contribution to journalArticle

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