A reactive molecular dynamics simulation of the atomic oxygen impact on poly(p-phenylene-terephthalamide)

L Liu and CQ Miao and D Song and JF Shi and WX Liu, COMPUTATIONAL MATERIALS SCIENCE, 228, 112341 (2023).

DOI: 10.1016/j.commatsci.2023.112341

Poly(p-phenylene-terephthalamide) (PPTA) is widely used in spacecraft structures due to its excellent mechanical properties and thermal stability. The space environment resistance of PPTA is the key factor affecting its service life. However, the mechanisms of the erosion process of PPTA during Atomic oxygen (AO) impact, which is one of the main factors for polymer degradation in the low earth orbit, remain unclear. In this study, the degradation mechanisms of PPTA under the AO impact are investigated by analyzing the morphology evolution, mass loss, the distribution of temperature, and the small molecules produced with simulation time using the ReaxFF reactive force field molecular dynamics simulations. The results show that the degradation mechanism of crystalline polymers due to the AO impact is closely related to the direction of the AO incidence. Throughout the simulation, the (010) surface has more mass loss and more CO and CO2 production, showing worse degradation than the (001) surface. This is due to the different temperature distributions of the two models caused by kinetic energy transfer in different crystal orientations. The extremely high local temperature on the surface of the (010) model leads to faster disintegration of the material. The simulation results can be used to provide atomic-scale insight into the design of crystalline polymers and their composites to resist atomic oxygen erosion.

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