Hydrogen-bonded PEG/functionalized expanded graphite composite phase change material (PEG/FEG CPCM) for pavement thermal regulation: Fabrication and performance

Polyethylene glycol (PEG) demonstrates significant advantages in asphalt pavement thermal regulation owing to high latent heat and adjustable phase transition temperatures. However, its limitations, including liquid-phase leakage and low thermal conductivity, restrict practical applications. This study developed a functionalized expanded graphite (FEG) matrix via acid oxidation, where oxygen-containing groups establish hydrogen bonds with PEG, forming PEG/FEG CPCM with enhanced thermal conductivity and encapsulation stability. Structural characterization showed FEG interlayer spacing increased from 0.3379 nm to 0.3439 nm, with surface oxygen content rising from 2.66 % to 12.33 % (predominantly −OH/−COOH groups). Hydrogen bonds forming between FEG and PEG restrict molecular chain migration, thereby improving encapsulation stability. The optimized PEG/FEG CPCM exhibited latent heats of 141.60 J/g (melting) and 134.12 J/g (crystallization), a 24.9 % lower supercooling degree (11.39°C vs. 15.17°C), and 11.58-fold higher thermal conductivity (3.6257 W/(m·K) vs. 0.3132 W/(m·K)) compared to pure PEG. Hydrogen bonding increased the decomposition temperature of PEG/FEG CPCM by 10.7°C to 306.4°C, with only a 0.9 % reduction in phase transition temperature and a 1.0 % latent heat loss after 100 thermal cycles. Field tests showed that PEG/FEG-modified asphalt mixtures extended heating/cooling durations by 2.1 %/15.0 %, mitigating pavement thermal distress. The study advances the application of PEG-based CPCMs to enhance pavement durability, mitigate UHI effects, and conserve energy.