Direct Observation of Short-Time Welding in UHMWPE Powders via X-ray Photon Correlation Spectroscopy and Magnetic...

We aim to elucidate the time scale over which welding between ultrahigh molecular weight polyethylene (UHMWPE) grains occurs by monitoring the dynamics of iron nanoparticles located at their interfaces, using X-ray photon correlation spectroscopy (XPCS). Within just one min above the melting point, we observe abnormally fast nanoparticle dynamics that emphasize the rapidity of the sintering mechanism, being key for the processing of long-chains polymers, as compared to the much slower chains re-entanglement shown by Yang et al. (Macromolecules, 2024, 57 (18), 8779-8792), resulting in UHMWPE thermodynamic equilibrium. The XPCS results are corroborated by in situ SEM imaging and supported by a theoretical model describing pore resorption, together offering a comprehensive view of early stage dynamics in weakly entangled polymers. To further validate our findings, experiments performed under conventional conduction heating are replicated using induction heating, where iron nanoparticles serve as localized nanoheaters through "magnetic hyperthermia", yielding consistent conclusions.