Polyurethane macro-encapsulation for CH3COONa·3H2O-Na2S2O3·5H2O/Melamine sponge to fabricate form-stable composite phase change material

Abstract

Using nano-sized porous supporting materials as carriers to shape-stabilize phase change materials (PCMs) is leading currently. However, the high carrier proportion and the existence of “nonfreezing liquid layer” in the composite significantly reduce the phase change enthalpy of composite. In this work, macroporous Melamine sponge (MS) as lightweight semi-adsorbed supporting material and the eutectic hydrated salt of Na2S2O3·5H2O-CH3COONa·3H2O as PCM were introduced, and the enthalpy reduction of the PCM@MS composite was much smaller (within 5%). Subsequently, the solid polyurethane (PU) thin-layer was adapted to macro-encapsulate PCM@MS, by which PCM operated stably in a closed system, solving the leakage problem and eliminating salt corrosion. With the addition of 2% SrCl2·6H2O as nucleating agent, the eutectic hydrated salt PCM with the mass ratio of 72%Na2S2O3·5H2O-28%CH3COONa·3H2O processed a suitable melting point (41.45 °C), high enthalpy (186.6 J/g) and low supercooling (0.462 °C). The morphology of MS and the distribution of PCM in MS were investigated in detail. Leakage and thermal stability tests for PCM@MS@PU indicated that 2.5 mm PU thin-layer owned a prominent cladding effect on PCM@MS. Heat conductivity determination manifested that PCM@MS@PU presented a brilliant thermal insulation property. Moreover, its thermal performance difference was small after 150 thermal cycles. All these enable the application of PCM@MS@PU in radiant floor heating system and provide a new routine for shape-stabilizing PCMs with polymer-based macroporous supporting material and thin-coating material.