Fabrication of Paraffin/Sepiolite Composite Phase Change Coatings for Building Thermal Insulation

To develop energy-efficient building coatings with enhanced thermal energy storage performance, paraffin/sepiolite composite phase change coatings were prepared using ultrasonic-assisted acid-activated sepiolite as a supporting matrix. The effects of acid treatment duration on the structural properties of sepiolite and the performance of the resulting coatings were systematically investigated. The results showed that acid activation for 1 h produced the optimal pore structure, yielding a maximum internal specific surface area of 125.881 m2g−1. Longer treatment durations (>2 h) caused structural degradation and possible deterioration of pore structure. The paraffin/sepiolite composite phase change material prepared with JK-1 h exhibited a latent heat of 77.29 J g−1, outperforming that prepared with JK-2 h. Increasing the paraffin and CPCM contents enhanced the thermal storage capacity of the coatings; however, excessive CPCM loading deteriorated film integrity, resulting in cracking, reduced adhesion, and decreased hydrophobicity. Among all formulations, sample S3 demonstrated the best overall performance, with a latent heat of 33.51 J g−1, a pull-off strength of 5.9 MPa, and a water contact angle of 102.53°. Thermal cycling tests further confirmed its excellent thermal reliability and reusability. These findings indicate that paraffin/sepiolite composite phase change coatings have considerable potential for reducing building energy consumption and improving indoor thermal regulation.