Spreading of a viscoelastic drop on a solid substrate

TL;DR

This study investigates how viscoelastic drops spread on solid surfaces, revealing faster spreading and different dynamics compared to Newtonian drops, influenced by internal relaxation times and effective viscosity variations.

Contribution

It demonstrates the impact of viscoelasticity on spreading dynamics and introduces a simple perturbation model to explain experimental observations.

Findings

Viscoelastic drops spread faster than Newtonian drops under similar conditions.

The effect of viscoelasticity is observable at timescales comparable to the polymer's relaxation time.

A perturbation model qualitatively matches experimental results.

Abstract

We study the spreading of viscous and viscoelastic drops on solid substrates with different wettability. In the early stages of spreading, we find that the viscoelastic drop spreads with faster and a different power law than the Newtonian drop (i.e. aqueous glycerine solution) for the same zero shear rate viscosity. We argue that the effect of viscoelasticity is only observable for experimental time scales in the order of the internal relaxation time of the polymer solution or longer times. Near the contact line, the effective viscosity is lower for the viscoelastic drop than for the Newtonian drop. Together with its shear rate dependency, this difference in effective viscosity can explain the different spreading dynamics. We support our experimental findings with a simple perturbation model that qualitatively agrees with our findings.