Sharkskin and melt fracture of some biodegradable polymers

Sharkskin and melt fracture phenomena have been investigated in two commercial biodegradable polyestersaliphatic-aromatic co-polyester (AAC), poly(lactic acid) (PLA) and their blends. The study was conducted in a two bore capillary rheometer. It was observed that at high shear rates and stresses PLA exhibits sharkskin and gross melt fracture, while AAC exhibits only gross melt fracture. Experiments indicate that the blends exhibit both phenomena and that blending is beneficial for postponing the onset of flow instabilities to higher shear stresses.