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<p>The transition toward sustainable infrastructure demands protective coatings capable of withstanding severe environmental threats while facilitating circular end‑of‑life management. This study presents the design and integration of cerium‑doped zinc phosphate nanoparticles as a single‑phase, multifunctional smart filler for non‑isocyanate polyurethane (NIPU) coatings. Synthesised via co‑precipitation, these mesoporous nanoparticles physically reinforce the polyhydroxyurethane matrix at an optimal 3 wt% loading, shifting macroscopic breakdown to a 100% cohesive failure mode and enhancing substrate adhesion to 5.59&#xa0;MPa. During service, electrochemical impedance spectroscopy (EIS) demonstrated effective long‑term barrier protection. The composite maintained a high low‑frequency impedance of 1.17 × 10⁸ Ω·cm² after 30 days of saline immersion, preventing the complete barrier collapse observed in the baseline. Furthermore, in‑situ scanning electrochemical microscopy (SECM) confirmed that localised acidic pH drops at coating defects trigger the smart release of Zn²⁺ and Ce³⁺ ions, which precipitate to suppress Fe²⁺ oxidation currents to near‑zero levels. Under forced‑flaming conditions, the dispersed filler functions as a condensed‑phase intumescent flame retardant. Thermal decomposition of the nanoparticles liberates phosphoric acid, catalysing premature matrix dehydration and driving the formation of a carbonaceous char shield that reduces the peak heat release rate by 53%. Finally, demonstrating material circularity, the dormant filler acts as an internal catalyst when subjected to a pH 2 recycling bath. Triggered nanoparticle dissolution lowers the depolymerisation activation energy to 65.8&#xa0;kJ mol⁻¹, accelerating chemical breakdown. This acid‑catalysed hydrolysis yields &gt; 90% recovery of diol and diamine monomers, establishing a viable pathway for circular structural coating systems.</p>

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Cerium-Doped Zinc Phosphate Nanoparticles as a Multifunctional Filler for Corrosion Inhibition, Flame Retardancy, and Upcycling of Non-isocyanate Polyurethane Coatings

  • 期刊论文

  • 发表日期：

    2026年7月20日

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  • Vignesh Jagajeevan,
  • Vidhya Lakshmi Sivakumar

摘要

The transition toward sustainable infrastructure demands protective coatings capable of withstanding severe environmental threats while facilitating circular end‑of‑life management. This study presents the design and integration of cerium‑doped zinc phosphate nanoparticles as a single‑phase, multifunctional smart filler for non‑isocyanate polyurethane (NIPU) coatings. Synthesised via co‑precipitation, these mesoporous nanoparticles physically reinforce the polyhydroxyurethane matrix at an optimal 3 wt% loading, shifting macroscopic breakdown to a 100% cohesive failure mode and enhancing substrate adhesion to 5.59 MPa. During service, electrochemical impedance spectroscopy (EIS) demonstrated effective long‑term barrier protection. The composite maintained a high low‑frequency impedance of 1.17 × 10⁸ Ω·cm² after 30 days of saline immersion, preventing the complete barrier collapse observed in the baseline. Furthermore, in‑situ scanning electrochemical microscopy (SECM) confirmed that localised acidic pH drops at coating defects trigger the smart release of Zn²⁺ and Ce³⁺ ions, which precipitate to suppress Fe²⁺ oxidation currents to near‑zero levels. Under forced‑flaming conditions, the dispersed filler functions as a condensed‑phase intumescent flame retardant. Thermal decomposition of the nanoparticles liberates phosphoric acid, catalysing premature matrix dehydration and driving the formation of a carbonaceous char shield that reduces the peak heat release rate by 53%. Finally, demonstrating material circularity, the dormant filler acts as an internal catalyst when subjected to a pH 2 recycling bath. Triggered nanoparticle dissolution lowers the depolymerisation activation energy to 65.8 kJ mol⁻¹, accelerating chemical breakdown. This acid‑catalysed hydrolysis yields > 90% recovery of diol and diamine monomers, establishing a viable pathway for circular structural coating systems.