Bio-Based, Nano-Reinforced Phase Change Composites for Marine Engineering: Formulation, Stability, and Heat-Buffering Performance

Abstract

International shipping faces tightening decarbonization targets, making compact peak-shaving solutions for shipboard HVAC and cold-chain loads increasingly valuable. This work develops a bio-based shape-stabilized PCM (SSPCM) using beeswax (BW) as the latent phase, sago starch (SS, 20 wt%) as the confinement matrix, and reduced graphene oxide (rGO, 0–1.50 wt%) as a nano-reinforcement; soy lecithin (0.5 wt%) is fixed as a dispersant. Thermal transport improved with rGO: thermal conductivity increased from 0.24 ± 0.01 to 0.37 ± 0.01 W/m·K and diffusivity from 1.25 ± 0.06 to 2.05 ± 0.08×10^-7 m²/s, reducing the 15-mm diffusion timescale from 30.00 to 18.29 min. After 500 melt–freeze cycles, latent-heat retention improved from 88% (F0) to 92% (F4), with lower melting-peak drift (+0.30→+0.15 °C) and reduced supercooling drift (0.50→0.27 °C). Melt-hold leakage at Tm, peak+5 °C for 4 h decreased from 2.8% (F0) to 1.5% (F4). In a 6 h hot-side pulse panel test, F4 achieved a peak inner-surface reduction of 3.9 °C, a time lag of 5.7 h, and a peak heat-flux reduction of 41.5%, translating to 15.5% peak cooling power and 22% compressor cycling reductions in an HVAC proxy. Encapsulation passed 70 °C/14-day screening, and RH/salt exposures retained 95–98.5% ΔHm with ≤0.60 abs% leakage increase. Vibration tests (5–200 Hz, 0.7 g) passed for F0–F5, while F6 was borderline after cycling.