Dynamic mechanical properties and low-velocity wetting behavior of plastic crystalline states for n-alkane blends

Steven J. Severtson, Michael J. Nowak

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Data presented here demonstrate a correlation between viscoelastic properties and wetting behavior for an n-alkane, binary mixture, and several macrocrystalline paraffin waxes. Mesophases in the premelting region of n-alkane systems were identified using differential scanning calorimetry, and their level of viscoelasticity was characterized via dynamic mechanical spectroscopy (DMS). Thermal analysis indicates that transitions between crystalline, plastic crystalline, and the isotropic phases for these systems coincide with peaks in loss tangent values measured using DMS. The combination of a broad range of viscoelastic properties and a relatively constant equilibrium contact angle over the premelting region provides a unique opportunity to study the relationship between substrate mechanical properties and wetting behavior. Dynamic contact angle measurements were performed for water on these surfaces using low substrate velocity (2-264 μm/s) Wilhelmy plate tensiometry. Advancing dynamic contact angles were found to have a velocity dependence that was greatly enhanced far removed from phase transitions, while equilibrium values were observed for receding angles at all substrate velocities and temperatures. Correlations were identified between loss tangent values for the substrate, phase transitions, and the magnitude and relaxation kinetics of advancing dynamic contact angles. Results clearly demonstrate that differences exist between wetting and dewetting mechanisms for water on n-alkane substrates. Advancing angle data could not be fit with models attributing contact angle behavior to substrate deformation, adsorption/desorption rates at the three-phase line, or hydrodynamic considerations. We speculate that observed results are associated with enhanced molecular freedom, which can be gauged by the mechanical loss tangent. Findings from this study may provide insight to anomalous wetting behavior reported for other low-energy substrates.

Original languageEnglish (US)
Pages (from-to)4990-4996
Number of pages7
JournalLangmuir
Volume17
Issue number16
DOIs
StatePublished - Aug 7 2001

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