EXCEPTIONALLY LARGE BANDED SPHERULITES

This article concerns the crystallization of maleic anhydride from a b lend containing 2 wt% of poly(acrylonitrile). High speed photography a nd temperature measurements during the crystallization as well as X-ra y diffraction from the blend after crystallization are consistent with a banded spherulitic morphology. The spacing of the bands, typically 4 to 15 mm, is two orders of magnitude larger than that reported in pr evious studies of the structure of banded spherulites. The velocity of the growth front is determined to be 33 cm/s when crystallization ini tiates from a solution supercooled by 28-degrees-C. X-ray diffraction patterns recorded using three orthogonal beam propagation -directions at different locations in the band structure show (within experimental error) that the blends have the twisting orientation of crystallites characteristic of banded spherulites. Interestingly, the bands caused by spherulitic crystallization of maleic anhydride are imprinted on th e polymer phase in the blend. This imprinting as well as the exception ally large band spacing in the crystallized blend may open the way for studies that would clarify the mechanism of formation of the twisting crystal orientation in banded spherulites.