Enhanced Thermal Buffering of Phase Change Materials by the Intramicrocapsule Sub per Mille CNT Dopant

Microencapsulation of a carbon nanotubes (CNT)-loaded paraffin phase change material, PCM in a poly(melamine-formaldehyde) shell and the respective CNT-PCM gypsum composites are explored. Although, a very low level (0.001-0.1 wt%) of intra-microcapsule loading of CNT dopant does not change the thermal conductivity of the solid, it increases the measured effusivity and thermal buffering performance during phase transition. The observed effusivity of 0.05 wt% CNT doped PCM reaches 4000 W s-0.5 m-2 K-1 which is higher than the reported effusivity of alumina and alumina bricks and an order of magnitude larger than the solid, CNT-free PCM powder. 0.015 wt% of CNT dopant in a 30 wt% PCM-plaster composite improved the effusivity by 60% compared to the CNT-free composite, whereas the addition of the same amount of CNTs to the bulk of the plaster does not improve either the effusivity or the thermal buffering performance of the composite. The thermal enhancement is ascribed to a CNT network formation within the paraffin core.