Yin Yu, Bohao Meng, Yuxin Fu, Shuhua Peng, Lisheng Xu, Qingshi Meng
Structural health monitoring in harsh environments demands scalable sensing coatings with exceptional mechanical robustness, weatherability and stability. We present a polyurea‑based nanocomposite spray sensing coating (PHSC). It integrates hexamethylene diisocyanate trimer-functionalized graphene nanoplatelets (HT‑GNPs) into a two‑component sprayable polyurea matrix. The covalent functionalization facilitates filler dispersion and network formation. The coating exhibits exceptional mechanical performance, achieving a tensile strength of 43.4 MPa and an elongation at break of 707.8% at 0.1 vol% of HT‑GNPs. The optimized formulation (2 vol% HT-GNPs) provides the best balance of properties, delivering robust piezoresistive sensing with gauge factors of 8.4 (0–235% strain) and 16.0 (>235% strain), along with rapid response (88 ms) and recovery (92 ms) times. The coating demonstrates excellent adhesion to diverse substrates (e.g., ceramic, automotive chassis) and maintains stable performance after damp-heat, salt-spray and UV-aging tests. Electrochemical analysis confirms robust corrosion resistance, exhibiting corrosion potentials of 0.23 V (H₂SO₄), 0.12 V (NaOH) and 0.15 V (NaCl). By combining rational molecular design with scalable spray processing, this work delivers a weather-resistant, multifunctional coating with promising potential for structural health monitoring in infrastructure and automotive applications.