Halogen‐Free Flame‐Retardant Composite Phase Change Material With 4‐Hydroxybutyl Acrylate Skeleton for Battery Thermal Management

ABSTRACT

Phase change materials (PCMs) are widely used in battery thermal management systems (BTMS) but face limitations in large‐scale applications due to flammability and leakage. In this study, 4‐hydroxybutyl acrylate (4HBA) is polymerized via free radical polymerization to construct a three‐dimensional (3D) network, which is then compounded with polyethylene glycol 2000 (PEG2000), expanded graphite (EG), and a halogen‐free phosphorus‐nitrogen flame retardant to form a novel composite phase change material (CPCM). Unlike traditional skeletons, which exhibit adsorption properties but are flammable, the 4HBA‐based polymer skeleton developed in this study contains a large number of hydroxyl groups. These not only provide structural support and adsorption but also participate in the charring process, thereby reducing the required amount of flame retardant. The resulting CPCM achieves a UL 94 V‐0 rating with a flame‐retardant loading of only 15 wt%, exhibits a latent heat of 81.99 J·g ⁻¹ , and exhibits a mass loss of only 1.9% after 14 h at 70°C. It also maintains structural integrity without cracking at 80°C and shows virtually no deformation at 100°C. By integrating flame retardancy, thermal performance, and mechanical properties within a 3D network structure, this CPCM provides a safe and reliable candidate for BTMS.