Development of polyurethane-based solid-solid phase change materials for cooling asphalt pavements

Abstract

Effective cool pavement technologies with using phase change materials (PCMs) are of great significance to alleviate Urban Heat Island (UHI) effect and improve the functionality, safety and service life of asphalt pavements. This study focuses on the development of polyurethanes (PUs) as solid–solid PCMs (s-s PCMs) that are suitable for asphalt pavement cooling utilizations. First, a range of PUs were synthesized through two-step polymerization reactions. Successful synthesis was confirmed by the Fourier transform infrared (FTIR) spectroscopy test. Next, characterizations were performed on the synthesized PUs. It is demonstrated that a PU with a larger isocyanate content usually sustains a higher temperature without liquid leakage. The applicable s-s PCM among the synthesized PUs is M_PU5 with 4,4′-diphenylmethane diisocyanate (MDI) as the isocyanate and the molar ratio of MDI and polyethylene glycol (PEG) being 5, due to its desirable latent heat storage capacity of 93.5 J·g−1 and phase change temperatures of 36–48.3 °C, excellent thermal stability and reliability, and its strong ability to withstand harsh conditions of asphalt pavements. Finally, the feasibility of M_PU5 for actively cooling asphalt pavements has been verified by outdoor test. The investigated results provide a basis and reference for building cool asphalt pavement systems with using s-s PCMs.