Online study of the formation of PA6 droplets in PP matrix under shear flow

Abstract

Breakup process of polyamide 6 (PA6) in polypropylene (PP) matrix under shear flow was online studied by using a Linkam CSS 450 stage equipped with op- tical microscopy. Both tip streaming and fracture breakup modes of PA6 droplets were observed in this study. It was reported that the droplet would break up by tip streaming model when the radio of the droplet phase viscosity to the matrix phase viscosity (Zr ¼ Zd/Zm) is smaller than 0.1 (Taylor, Proc R Soc London A 1934, 146, 501; Grace, Chem Eng Commun 1982, 14, 225; Bartok and Mason, J Colloid Sci 1959, 14, 13; Rumscheidt and Mason, J Colloid Sci 1961, 16, 238; de Bruijn, Chem Eng Sci 1993, 48, 277). However, the tip streaming model was observed even when the viscosity ra- tio was much greater than 0.1 (Zr ¼ 1.9). In this study for the tip streaming mode, small droplets were ruptured from the tip of the mother droplet. On the other hand, the mother droplet was broken into two or more daughter droplets with one or several satellite droplets between them for the frac- ture mode. It was found that PA6 droplet was much elon- gated at first, and then broke up via tip streaming or fracture to form daughter droplets or small satellite droplets with the shape of fiber or ellipse. Stopping shearing, those elongated droplets began to shrink, and finally became spheres. More- over, it was found that the average domain size of those PA6 spheres considerably decreased with increasing shear time. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2690- 2695, 2007