Abstract
A new kind of self-organized transient fingering pattern and instability was found to generally exist during the adhesive contact and coalescence of two polymer films in the viscous or viscoelastic state. The average radius of the patterns was found to increase with contact time following r = (r i + r o)/2 ∞t n, where r o and r i, are the outer and inner radii of the fingers, and where n varies from 0.15 to 0.3 depending on the viscoelastic properties of the materials. The surface approach rate has no effect on the appearance of the fingering patterns once it is less than some critical rate. The lifetime of the fingering patterns increases with the polymer viscosity as τ ∞ η n (n = 1.6 ±0.2), and peaks at some critical film thickness. The mechanism for the transient patterns is discussed in terms of theoriesof fluid mechanics and the molecular forces between surfaces.
Original language | English (US) |
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Pages (from-to) | 8409-8422 |
Number of pages | 14 |
Journal | Macromolecules |
Volume | 40 |
Issue number | 23 |
DOIs | |
State | Published - Nov 13 2007 |
Externally published | Yes |