Comparation of Polyethylene and Polypropylene on the Time-Temperature Superposition Principle by Molecular Dynamics Simulations

• Published in: Advanced Experimental Mechanics Vol. advpub
• Main Authors: YUAN Shihong, SAKAI Takenobu
• Format: Journal Article
• Language: English; Japanese
• Published: The Japanese Society for Experimental Mechanics 2025; 日本実験力学会
• Subjects: Creep; Molecular dynamic simulations; Polyethylene; Polypropylene; Time-temperature superposition principle
• ISSN: 2189-4752; 2424-175X
• DOI: 10.11395/aem.25-0001

Polymers and their composites are widely used in aerospace, energy, and automotive industries due to their lightweight, manufacturability, and high impact resistance. Predicting the viscoelastic behavior of these materials is crucial for ensuring their reliability and durability. The Time-Temperature Superposition Principle (TTSP) is commonly used to predict long-term viscoelastic properties like creep and stress relaxation, but its molecular mechanisms are not fully understood. This study employs molecular dynamics simulations to investigate these mechanisms in polyethylene (PE), and polypropylene (PP) with methyl group. Creep analyses at various temperatures show that PP exhibits superior creep resistance compared to PE. Furthermore, the role of free volume was examined, showing that the methyl groups in PP contribute to more stable free volume changes. This study also shows the importance of torsion potential energy for TTSP and demonstrates that the presence of methyl groups primarily affects TTSP through bond and angle potential energies. This study clarified the effect of the presence or absence of methyl groups on TTSP.