Polyalcohols such as neopentyl glycol (NPG) undergo solid-state crystal transformations that absorb/release sufficient latent heat. These solid-solid phase change materials (PCM) can be used in practical thermal management applications without concerns about liquid leakage and thermal expansion during phase transition. In this paper, microcapsules of NPG encapsulated in silica shell were successfully synthesized with the use of the emulsion technique. The size of the microcapsules was in the range of 0.2–4 μm, and the thickness of the silica shell was about 30 nm. It was found that the endothermic event of the phase change behavior of these NPG-silica microcapsules was initiated at around 39 °C and the latent heat was about 96.0 J/g. A large supercooling of about 43.3 °C was observed in the pure NPG particles without shell. The supercooling of the NPG microcapsules can be reduced to about 14 °C due to the heterogeneous nucleation sites provided by the silica shell. These NPG microcapsules were added into heat transfer fluid PAO to enhance its heat capacity. The effective heat capacity of the fluids can be increased by 56% by adding 20 wt. % NPG-silica microcapsules.

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