Melt Fracture of Polymer Thin Film at Strongly Attractive Surfaces

Abstract

In this study, we report an interesting phenomenon of “melt fracture” which was observed when a high viscosity film dewets from a film of lower viscosity. We propose that this phenomena is similar to the “melt fracture” or “shark skin” that is observed when extruding bulk polymer. We hypothesized that the “melt fracture” occurs as a result of shear which is imposed by the dewetting layer on the visco-elastic lower layer. The dewetting layer is adhered to the lower layer via entanglements across the polymer/polymer interface. When the other interface of the liquid film is adsorbed to an attractive substrate interface, a velocity gradient occurs in the film and therefore can result in the shear gradient. We proposed that if this shear rate exceeds the natural reptation time, melt fracture of thin film resulted. Screening the substrate interaction by first deposition a very thin layer of immiscible polymer such as poly (vinyl-pyridine) PVP reduced the degree of melt fracture. A DI 3000 Atomic Force Microscopy (AFM) was used to quantify the depth and the dynamics of the melt facture process.