The Effect of Rare Earth beta-Nucleating Agents on 1-Butene Bulk Polymerization and Crystallization Behavior

Poly (1-butene) was modified with rare earth beta-nucleating agents which were introduced in situ during bulk polymerization of 1-butene. The influence of nucleating agent amount on the molecular weight, melting temperature (T-m), degree of crystallinity (X-o), and crystallization behavior of resulting poly (1-butene) was investigated in detail by gel permeation chromatography (GPC), differential scanning calorimeter (DSC), polarizing microscopy (POM), and wide angle X-ray diffraction (WAXD). The results show that with the increase of nucleating agent content the isotacticity of poly (1-butene) was slightly increased, the number-average molecular weight (M-n) was obviously improved and the molecular weight distribution was narrowed while the activity of Ziegler-Natta catalyst was somewhat decreased. The addition of rare earth beta-nucleating agents changed the crystallization behavior of polymers, the spherulite size of nucleated poly (1-butene) dramatically decreased compared with that of pure poly (1-butene) and tends to homogenization with the increasing of nucleating agents content, the X-e of poly (1-butene) is improved, especially when the addition of beta-nucleating agents is 300 mg, but dropped dramatically after this point. In addition, the rare earth beta-nucleating agents not only play an positive role in improving T-m by changing the proportion of forms I' and III, but also speed up the transformation of crystalline form from II to I, shorten the crystal transformation period.