Enhancing light-to-thermal conversion performance of flexible EPDM/GNPs/PW phase change composites via salt-assisted EG exfoliation

The development of high-efficiency energy conversion and storage systems for stable and controllable solar energy utilization remains a major challenge. Organic phase change materials (PCMs), such as paraffin wax (PW), show promise in addressing this issue but are limited by leakage problems, inadequate flexibility, and low light absorption efficiency. To address these challenges, this study develops a scalable, salt-assisted roll-to-roll processing strategy to fabricate flexible phase change composites (PCCs) with excellent light absorption capability and effective encapsulation of PW. This strategy employs a synergistic mechanical force and salt template interactions to simultaneously exfoliate expanded graphite (EG) and orient the resulting nanoplatelets in-plane. The resulting EPDM/GNPs/PW PCCs exhibit a densely packed, aligned architecture of graphite nanoplatelets (GNPs), which significantly enhances the light-absorption area and markedly increases the light absorption efficiency from 39.9% to 93.7%. Moreover, the incorporation of GNPs as a reinforcing phase, which also provides an anchoring effect on the PW, contributes to a tensile strength of 4.8 MPa, an elongation at break of 1108.1%, and an initial latent heat of 106.4 J/g. Remarkably, the composites retain a latent heat (ΔH m ) exceeding 100 J/g after 500 thermal cycles, demonstrating exceptional durability. Consequently, this work offers a cost-effective and scalable strategy for fabricating highly flexible PCCs with efficient light-thermal conversion, holding promise for advancing solar energy applications.