Phase change materials (PCMs) have exhibited significant potential for thermal management in buildings, but their widespread application is hindered by inherent drawbacks including leakage, low thermal conductivity, and flammability. To simultaneously address these issues, this study designed a novel multifunctional composite PCM based on polyimide (PI) aerogel. The PI aerogel was prepared by a polycondensation reaction into poly(amic acid), followed by freeze-drying and thermal imidization. Octadecane (OD) was then encapsulated within this matrix using vacuum impregnation to form the phase change composite (PI@OD). To improve the composite performance, amino-functionalized carbon nanotubes (ACNT) were integrated into the aerogel. The PI@OD composites were characterized via thermophysical property and microstructural tests. Results demonstrate that the PI@OD-5 (containing 5 wt% ACNT) exhibits insignificant leakage after 6 h heating at 80 ℃. It possesses a high latent heat of 163.3 J/g and shows a 47.19 % enhancement in thermal conductivity compared with the pristine PI aerogel. The composite also shows superior flame retardancy. Its peak heat release rate and total heat release are significantly reduced by 80.2 % and 68.1 % compared with pure OD. Moreover, the integration of ACNT enables an ultra-fast fire warning response within merely 3.5 s upon flame exposure, drastically outperforming conventional alarm systems (∼100 s). This work successfully integrates efficient thermal management, robust flame retardancy, and rapid fire-warning into a single composite, presenting a promising and innovative solution for developing energy-efficient and fire-safe building envelopes.
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