Thermal and rheological framework for PCM‑infused paint coatings on high‑speed rail profiles

Railway infrastructure has been severely damaged by extreme heat, which causes structural stress and thermal expansion. We looked into phase change material (PCM)-integrated heat-resistant paints for improved thermal regulation and coating stability on web, flange, and head surfaces in order to control rapid temperature changes in rail components. An acrylic emulsion paint was mixed with two PCMs (melting points of 28 °C and 45 °C) at 15 wt% and 30 wt%, respectively. A maximum latent heat storage of 79.76 J/g (PCM45-30) was confirmed by differential scanning calorimetry, and rheological tests revealed that the viscosity increased from 1.24 Pa·s to 4.03 Pa·s and the yield stress increased from 9.43 Pa (control) to 172.7 Pa. In comparison to the control, thermal performance tests showed a cooling time of 12 minutes and a peak surface temperature reduction of up to 5 °C. For PCM45-30, a Carreau-Yasuda-based model predicted maximum coating thicknesses of 7.95 mm on a 13° incline, 3.62 mm on a vertical (90°) face, and 1.79 mm on a horizontal (0°) surface. These results highlight the two advantages of PCM integration: significant passive heat reduction and adjustable workability. They also suggest that PCM45-based formulations are good options for long-term thermal protection of high-speed rail profiles.