Highly Stable Composite Phase-Change Materials Reinforced by Silica Aerogels and Cellulose Nanocrystals for Enhanced Thermal Insulation and Durable Isoperibolic Application

The reduction in thermal conductivity of composite phase-change materials (PCMs) enhanced with silica aerogels (SAs) is garnering interest across various fields. However, the integration of SAs into substrates poses a challenge due to their high specific surface area and lightweight properties. In this research, we successfully developed a PCM reinforced with SA and cellulose nanocrystals (CNC) (paraffin wax (PW) @CNC/SA @poly(vinyl alcohol) (PVA), PW@CNC/SA@PVA). Here, renewable CNCs function as effective Pickering emulsifiers for encapsulating PW, while PVA acts as a binder, stabilizing the SA and maintaining its nanoporous integrity. The amphipathic nature of CNCs plays a crucial role in securely encapsulating PW with an impressive content of 63 wt %. The specific latent heat capacity of PW@CNC/SA@PVA was measured to be approximately 106 J/g. Remarkably, this material exhibited minimal leakage (about 2 wt %, over 2 h) at temperatures exceeding its melting point (60 °C). Additionally, the uniform dispersion of hydrophobic, porous SAs within the PVA solution imparts PW@CNC/SA@PVA with a unique blend of low thermal conductivity and ultralight properties. In a simulated scenario resembling sunlight exposure, the designed PW@CNC/SA@PVA demonstrates significant potential for long-term isoperibolic applications.