  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.
