Analysis of surface structure with regard to interfacial delamination in polyester films with incompatible polymers

Abstract

AbstractPoly(ethylene terephthalate) (PET) films containing incompatible polymer particles were analyzed, with particular reference to the relationship between the PET particle interfacial tension and the microvoids, or the protrusion that were formed when the composite material was stretched at 90°C. A model was developed to simulate void formation and surface protrusion due to interfacial delamination between PET and three types of dispersed incompatible polymers, poly(4‐methyl‐1‐pentene), polypropylene, and polystyrene. The numerical results, obtained with the finite element method, were compared with experimental data of the blends for both the internal and subsurface regions. The experimental measurements showed that the increase in the difference in the surface tension between PET and the added incompatible polymer was associated with the formation of larger voids. The protrusions were also generated in the stretching and delamination between PET and the incompatible polymers, but a decrease in the interfacial tension agreed with the formation of a larger protrusion. Modeling studies showed that increasing the interfacial tension between the two components in a blend causes a decrease in the critical stress for delamination. Interfacial tension values related qualitatively to the critical stress for void formation and protrusion calculated with the numerical analysis. A concavity was also necessary for understanding the surface structure of the films, along with protrusion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1243–1251, 2004