Thermal energy storage characteristics of polyacrylic acid/dodecanol/carbon nanofiber composites as thermal conductive shape-stabilized composite phase change materials

Thermal conductive shape-stabilized composite phase change materials (PCMs) were produced using polyacrylic acid (PAA), dodecanol (DDA) and carbon nanofiber (CNF) by solution blending route. In the composites, DDA was used as the material with latent heat thermal energy storage (LHTES) capability and PAA was introduced as the main supporter and shape stabilizer material for DDA. CNF was employed for two reasons: (i) to enrich the heat-storing/releasing rate of the polymer-based composite as the conductive nanofillers and (ii) to contribute to increasing the DDA adsorption rate in the shape-stabilized composites. In this regard, a series of LHTES materials were presented, comprising of PAA/DDA composite, and PAA/DDA composite PCMs doped with CNF of 4 and 10 wt%. Composite PCMs exhibited well shape stabilization performance even with a high amount of DDA (70 wt%) due to both the cross-linked spatial structure of PAA and the uniform dispersion of CNF in the composite. Fourier transform infrared spectroscopy and X-ray diffraction findings indicated that there was no chemical bonding in PAA/DDA or PAA/DDA/CNF composites. DSC analysis revealed the highly favourable LHTES properties of the PAA/DDA(70 wt%)/CNF(10 wt%) composite, melting at 18.04°C and having a phase change enthalpy as high as 157.03 J/g. The thermal gravimetric analysis results showed that this composite had excellent thermal resistance to mass degradation up to 125°C. Thermal conductivity measurements indicated the significant effect of the CNF doping on the increment of the thermal conductivity of the PAA/DDA composite. All test results suggest that especially shape-stabilized PAA/DDA/CNF composite PCM can be evaluated as energy-saving materials for thermal management of buildings.