BETA-NUCLEATORS AND BETA-CRYSTALLINE FORM OF ISOTACTIC POLYPROPYLENE

Different levels of beta-form crystallinity in isotactic polypropylene (IPP) were produced by blending a series of additives. X-ray diffract ion analyses showed that the Kx values varied from 0 to 0.95. Indigoso l Brown IRRD, Indigosol Red Violet IRH, Cibantine Orange HR, Indigosol Pink IR, Cibantine Blue 2B, Indigosol Golden Yellow IGK, and Indigoso l Grey IBL were found to be effective beta-nucleators. The respective Kx values of the iPP samples containing the above seven beta-nucleator s of 0.05 wt % are 0.54, 0.68, 0.82, 0.82, 0.86, 0.92, and 0.95. All t he beta-nucleators possess fused benzene rings or heterocycles in thei r molecular structures. X-ray diffraction studies on them revealed a m utual character in that the strongest or the second-strongest reflecti ons almost locate at the d-spacing of 2.83 Angstrom. The magnitude is about half of that of the beta-form crystallinity d-spacing (5.64 Angs trom). The beta-form level also depends an a number of factors under o ur control, such as the beta-nucleator concentration, cooling rate, cr ystallization temperature, and melt temperature. Polarizing microscope observations suggested that beta-spherulites possess a bright color a nd that their Maltese Crosses display some concentric banding of a rat her spiky, jagged character. Their lamellae exhibit a correlated and d endritic structure seen by a scanning electron microscope. (C) 1995 Jo hn Wiley and Sons, Inc.