Dewetting dynamics of sheared thin polymer films: an experimental study

TL;DR

This experimental study investigates how shear influences the dewetting behavior of ultra-thin molten polymer films, revealing that shear accelerates hole growth and alters their shape, with a model explaining these effects.

Contribution

It introduces a model that accounts for shear-thinning and capillary forces to explain dewetting dynamics under shear in thin polymer films.

Findings

Shear increases the growth speed of dewetting holes.

Shear modifies the shape of dewetting holes to an ellipsoid.

The proposed model captures the experimental observations effectively.

Abstract

An experimental investigation is reported on the effect of shear on the bursting of molten ultra-thin polymer films embedded in an immiscible matrix. By using an optical microscope coupled with a shearing hotstage, the dewetting dynamics, i.e. the growth of dewetting holes is monitored over time at various shear rates. It is observed that their circularity is modified by shear and that for all temperatures and thicknesses studied, the growth speed of the formed holes rapidly increases with increasing shear rate. A model balancing capillary forces and viscous dissipation while taking into account shear-thinning is then proposed and captures the main features of the experimental data, such as the ellipsoid shape of the holes and the faster dynamics in the direction parallel to the shear. This research will help to understand the instabilities occurring during processing of layered polymeric structures, such as multilayer coextrusion.