Development of Structural Model of Strain-Hardening Behavior of Semi-Crystalline Polymeric Solids

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K15345
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 35020:Polymer materials-related
• Research Institution: Japan Advanced Institute of Science and Technology (2021); Nagoya University (2020)
• Principal Investigator: Kida Takumitsu 北陸先端科学技術大学院大学, 先端科学技術研究科, 助教 (40866290)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: ひずみ硬化 / 結晶性高分子 / 力学物性 / タイ分子 / 分子量分布

Outline of Final Research Achievements

The macroscopic stress increases with increasing strain before the fracture of polymeric materials, which is called strain-hardening behavior" for various semi-crystalline polymers such as polyethylene (PE). The structural interpretation of the strain-hardening behavior is essential to improve the mechanical properties of polymers because the strain-hardening behavior strongly correlates to the strength and toughness of polymer materials.
In this study, PE samples with controlled amounts of specific molecular weight components were prepared. The amount of the molecular weight lower than 300,000 had no influence on the strain hardening, although the strain hardening was significantly improved by increasing the amount of the molecular weight higher than 300,000. These results suggest that the tie molecules connecting 6 lamellar crystalline layers act as stress transmitters between crystals, and the amount of the tie molecules connecting 6 lamellae dominates the strain-hardening behavior.

Free Research Field

高分子物理

Academic Significance and Societal Importance of the Research Achievements

結晶性高分子のひずみ硬化挙動はこれまで精力的に研究が行われてきた。特に、超高分子量の分率を増加させることでひずみ硬化性が向上することは報告されてきたが、ひずみ硬化性向上のメカニズムは理解されていなかった。本研究の成果を用いれば、ひずみ硬化性を効果的に改善するために必要な分子量分布を予測することが可能となり、従来の結晶性高分子と比較して劇的にひずみ硬化性および強度を改善することが可能となる。本研究ではPEをモデル試料として用いているが、ポリプロピレンなど他の結晶性高分子にも適用することができ、多くの結晶性高分子の物性改善が期待される。