材料期刊网

以基于Cr系催化剂、不同己烯含量的管材用乙烯己烯共聚物为研究对象, 应用1H固体NMR技术测定了其室温下的相结构参数以及不同温度下的相结构变化. 研究发现, 随着共聚单体含量的增加, NMR结晶相组分的含量降低,  界面区和无定形区组分含量增加, 且两者在NMR测定的长周期中所占的比例也增加. 提出了以界面区含量和无定形区含量的比例随温度的变化作为定性判断非晶区中链段运动受限程度的依据. 此外, 采用相同的1H固体NMR技术研究了不同耐压等级聚乙烯管材料基体树脂的聚集态结构. 发现室温下随着管材料耐压等级的增加, 结晶相组分含量减少而其他两组分含量增加, 且NMR测定的长周期中结晶相组分所占比例降低而其他两组分比例升高. 实验结果证明, 上述定性判断非晶区中链段运动受限程度的判据与材料的耐压等级有较好的对应关系.

Using different  ¹H solid--state NMR techniques, the Cr--catalyzed ethylene--hexene copolymer with different hexene content was investigated, and the effects of comonomer content on the phase composition, molecular
mobility and domain size of the copolymer were studied. The results showed that the mass fraction of crystalline phase was decreased with the hexene content increasing, while the fractions of the other two components were
increased. Meanwhile, the fraction of the interface and amorphous component was increased in the NMR long period. Furthermore, we choose the variance of M_I/M_A , the ratio of mass fraction of interface component to the fraction of amorphous component, with temperature as the qualitative determination of the confined degree of the segment in non--crystalline  region. Cr--catalyzed PE copolymer for pipe application with different duration grade was investigated. It was found that the mass fraction of rigid component decreased with the duration-grade increasing, while the fractions of the other two components increased. The same trend of the fraction in NMR long period was illustrated by the ¹H spin diffusion result. The variance of  M_I/M_A showed great correspondence to the duration grade of the materials.