Assessment of the contrasting effects of 0D and 1D nanostructures on the long-term stability of recycled poly(p-phenylene terephthalamide)

This study aims to explore, for the first time, the contrasting effects of 0D and 1D nanoestructures on the long term environmental stability of recycled poly(p-phenylene-terephthalamide) (PPTA). While carbon nanotubes (CNT) have been previously used to enhance virgin PPTA, their impact on recycled PPTA and its aging behavior remains largely unexplored. Moreover, no prior reports have addressed the comparative degradation pathways induced by titanate nanotubes (TTNTs) and Cu₂O nanoparticles in this high performance polymer. By adding 0.04 wt.% of multi-walled CNTs (MWCNTs) to a recycled PPTA paste to form hybrid sheets, the tensile strength of the polymer composite increases by 19.3% compared to the neat recycled PPTA. In contrast, recycled PPTA sheets containing Cu₂O-NPs showed a decrease on this property of 58%, while PPTA sheets filled with TTNTs fractured just by handling. x-ray diffraction and x-ray photoelectron spectroscopy (XPS) analyses of the PPTA composites after being prepared (<i>t</i>= 0) and after exposure to ambient conditions for 4-5 years, including<i>in situ</i>UV-irradiated XPS analysis of PPTA + MWCNTs, showed that the crystalline planes of PPTA + MWCNTs remained stable over time compared to other composites. Additionally, the C1s core level revealed a significant reduction in carbonyl functionalities (C=O) in the recycled PPTA matrix after reinforcing with MWCNTs. This suggests effective molecular-level healing, which inhibits oxidative degradation pathways by limiting oxygen-related bonding within the main polymer structure.