Microstructural Interpretation of Influences of Molecular Weight on the Tensile Properties of High-Density Polyethylene Solids Using Rheo-Raman Spectroscopy
Microstructural Interpretation of Influences of Molecular Weight on the Tensile Properties of High-Density Polyethylene Solids Using Rheo-Raman Spectroscopy
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DOI：
10.1021/acs.macromol.0c02124
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发表时间：
2021-01-12
期刊：
影响因子：
5.5
通讯作者：
Nitta, Koh-hei
中科院分区：
文献类型：
--
作者：
Kida, Takumitsu;Hiejima, Yusuke;Nitta, Koh-hei
通过制备不同分子量、恒定多分散指数（M-w/M-n）的高密度聚乙烯（HDPEs），研究了重量-平均分子量（M-w）对结构-性能关系的影响。随着M-w的增加，层状晶层厚度增加，而非晶层厚度和tie-分子分数等非晶态特征保持不变。用原位拉曼光谱研究了这些hdpe的微观变形。取向参数< P-2 >在应变硬化区与M-w呈幂律关系，指数为-3/4。分子取向的M-w依赖性被解释为层状团簇单元的重新排列，其大小由聚合物链在熔融状态下的端到端距离决定。研究发现，低M-w的HDPEs结晶链受到较高的拉伸应力，这意味着形成了大量的拉紧链。
The influence of the weight-average molecular weight (M-w) on the structure-properties relationship was investigated by preparing high-density polyethylenes (HDPEs) of various M-w but constant polydispersity index (M-w/M-n) values. The thickness of the lamellar crystalline layer increased with increasing M-w, whereas the amorphous characteristics, such as the amorphous layer thickness and tie-molecule fraction, remained unchanged. The microscopic deformation of these HDPEs was investigated by in situ Raman spectroscopy. The orientation parameter < P-2 > showed a power law to M-w with an exponent of -3/4 in the strain-hardening region. The M-w dependence of the molecular orientation was interpreted as the realignment of the lamellar cluster units, the size of which was determined by the end-to-end distance of the polymer chains in their melt state. It was found that higher stretching stress is applied to the crystalline chains for HDPEs of lower M-w implying that a larger amount of taut-tie chains is formed.