采用核磁共振分析仪、差式扫描量热仪,研究了不同碳链长度极低密度聚乙烯树脂(PE-VLD)产品的支化组成分布和熔融结晶性能;分别选取了平均序列长度、相对单体分布、共聚单体竞聚率进行聚合特性分析;运用自成核退火热分级(SSA)处理,讨论了晶片厚度(L)、相对支化度(S)、结晶度(Xc)等结晶特性.结果表明,密度为0.912 g/cm3、熔体流动速率为1.0 g/10min的PE-VLD产品,以己烯为共聚单体(C6)制备的产品中共聚单体含量、S低于以丁烯为共聚单体(C4)产品;而Xc、L则要高于C4产品.%The branching composition distribution and melting-crystallization properties of very-low-density polyethylene PE-VLD with different chain lengths were investigated by means of 13C-NMR spectroscopy and differential scanning calorimetry.The polymerization characteristics of these PEVLD samples were analyzed on the basis of mean sequence lengths,relative monomer distribution and monomer reactivity ratios,and their crystallization characteristics including lamellar thickness,relative branching degree and crystallinity degree were investigated by SSA thermal classification method.The results indicated that,in the case of PE-VLD with a density of 0.912 g/cm3 and a melt flow rate of 1.0 g/10 min,the sample synthesized by using a butylethylene comonomer exhibited a lower content of copolymerized segment and a lower branching degree than that using a butylene comonomer.However,it had higher crystallinity degree and thicker crystalline lamellas.
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