THE EFFECT OF VISCOSITY RATIO ON THE PHASE INVERSION OF POLYAMIDE-66 POLYPROPYLENE BLENDS

The theological properties of the blend components are an important pa rameter in the formation of a blend morphology. The effect of viscosit y ratio on the morphology of polyamide 66/polypropylene blends was stu died, with primary attention to the phase-inversion behavior and the a verage particle size of the dispersed phase. The relationship between the mechanical properties and the phase-inversion composition was inve stigated as well. Noncompatibilized and compatibilized blends having f ive different viscosity ratios were prepared by twin-screw extrusion. Maleic anhydride-grafted polypropylene was used as the compatibilizer to increase the adhesion between the two polymers and to stabilize the blend morphology. Investigation of the morphology of the blends by mi croscopy (SEM and TEM) showed that the smaller the viscosity ration (e ta(PA)/eta(PP)) the smaller was the polyamide 66 concentration at whic h the phase inversion took place and that polyamide 66 became the cont inuous phase. The results are in accord with the model of Jordhamo. Th e compatibilizer induced a sharp reduction of particle size, but did n ot have a major effect on the phase-inversion point. The tensile and i mpact properties of the compatibilized blends were found to correlate with the phase inversion. An improvement in the mechanical properties was observed when polyamide 66 provided the matrix phase. (C) 1994 Joh n Wiley and Sons, Inc.