An investigation into the mechanisms underlying the impact of stretching on the conductivity and band structure of polyethylene

Abstract Polyethylene is extensively utilized in various applications, such as capacitors, submarine cable insulation, lithium-ion battery separators, and other fields, because of its superior insulation properties. However, these materials are inevitably subjected to mechanical stress, which leads to alterations in their internal micro structures. These changes subsequently impact charge transport and ultimately degrade their insulation capabilities. Stretching can also affect the breath ability and thermal stability of battery separators. To investigate the structural characteristics of polymers under tensile conditions, this study undertakes a comprehensive analysis of the tensile behavior, trap characteristics, and band structure of polyethylene materials using experimental testing, molecular dynamics simulations, and first-principles calculations, revealing that upon reaching the yield point after stretching, the microscopic free-volume distribution rate increases by 2.97%. Currently, new electronic states have emerged within the band structure. At the mesoscopic level, a notable decrease of 36.4% in the trap density was observed. As the strain intensified, the free volume exhibited a slight increase and subsequently stabilized. Furthermore, more energy level splitting and the formation of new energy levels occur, predominantly owing to the s-orbitals of hydrogen atoms, reaching a peak density of 46.861 eV −1 . This led to an increase in the number of deep traps, which captured a greater number of electrons or holes, thereby enhancing the charge by 152%. The results are expected to provide a new theoretical basis for the synergistic regulation of polymer materials under electric and force fields, as well as for the evaluation of equipment operation under various working conditions.