稀土β-成核剂对1-丁烯本体聚合和产物聚(1-丁烯)结晶性能的影响

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

采用Ziegler-Natta催化剂催化1-丁烯本体聚合,稀土β-成核剂经原位聚合的方法加入到体系,并考察成核剂加入量对产物聚(1-丁烯)的分子量和结晶性能的影响.通过凝胶渗透色谱(GPC)、示差扫描量热仪(DSC)、偏光显微镜(POM)和广角X射线衍射仪(WAXD)对聚合物进行表征分析.实验结果表明,随着稀土β-成核剂加入量的增大,催化剂活性有所下降,聚合物等规度略有提高,而聚合的分子量显著提高,分子量分布变窄;聚合时成核剂的加入提高了聚(1-丁烯)的结晶性能,随着成核剂加入量的增多聚合物晶粒变小且尺寸趋向均一化,聚合物结晶度也得到了提高,当成核剂加入量为30 mg时,聚合物结晶度和熔融焓出现突变现象.此外,稀土β-成核剂的加入会改变熔融前聚(1-丁烯)中晶型Ⅰ'和Ⅲ所占比例从而影响聚合物的熔点,成核剂的存在也改变了晶型II向晶型I的转变速率,缩短了晶型转变周期.

Poly（1-butene） was modified with rare earth β-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（ Tm）,degree of crystallinity（χc）,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 numberaverage molecular weight（ Mn） 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 β-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 χcof poly（1-butene） is improved,especially when the addition ofβ-nucleating agents is 300 mg,but dropped dramatically after this point. In addition,the rare earth β-nucleating agents not only play an positive role in improving Tmby 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.