The Formation of Large Banded Spherulites in aComplex

We investigate the solidiication behavior of a maleic anhydride / polyacrylonitrile mixture in the banded spherulitic regime. In particular , we measure the velocity of the solidiication front and the resulting wavelength of the bands as the undercooling T is varied. The observed dynamics are representative of that seen in a large class of highly viscous uids that have been solidiied well below their melting temperature. The mechanism for banding seen in spherulitic growth is poorly understood, and while there is no generally accepted model, several have been proposed. One these, thèsolitonic model', predicts that the ratio between the light and dark portions of the bands should diverge as the undercooling is lowered toward a critical value T. Instead , we nd that the ratio between the light and dark bands remains approximately constant. In addition, our data is consistent with anèlastic twist' model proposed by Owen 1], in that the band spacing diverges as T ?3=2 .