Starch-based biodegradable blends:: morphology and interface properties

In order to improve the properties of plasticized wheat starch (PWS) and to conserve its final biodegradability, PWS can be blended with biodegradable polyesters [polyesteramide, poly(e-caprolactone), poly(lactic acid), poly(butylene succinate adipate) and poly(butylene adipate terephthalate)] which exhibit variable polar characteristics. This paper is focused on the analysis of the compatibility of these blends which vary according to their formulation. To understand the lack of affinity between the different phases, interface adhesion has been investigated by contact angle measurements to obtain the work of adhesion. From these determinations a forecast approach has been developed to predict blend compatibility. Blend structures were obtained by scanning electron microscopy observations. Blends show either a dispersed structure or a co-continuous morphology. Percolation thresholds (co-continuity) and full continuity regions were determined thanks to a method based on solvent extraction. Finally, rheological investigations have been carried out on the different biodegradable polymers to understand better the blend structure formation during the process. (C) 2004 Society of Chemical Industry.