LAUSR

Abstract A typical polyol that experiences solid-solid phase transitions, pentaerythritol (PE) has been proposed as a promising phase change material candidate for latent heat storage pertinent to the temperature range for industrial waste heat recovery. Upon increasing the temperature to over the solid-solid phase transition point (∼459 K), body-centered tetragonal crystalline structure of PE (α phase) is transformed into orientationally disordered face-centered cubic crystalline structure (γ phase). The thermal conductivity of PE at both α and γ phases is of great practical interest. In this work, the in situ X-ray diffraction and Fourier transformer infrared spectroscopy were used to characterize the crystalline structure transition of PE, in combination with the differential scanning calorimetry results. Molecular dynamics simulations were performed to elucidate the relationship between the thermal conductivity variation of PE and its crystalline structures at the atomic level. It was found that after the α-to-γ phase transition, the rearrangement and rotation of the O H···O bonds lead to indeterminate positions of the O and H atoms in the γ phase. The destruction and weakening of the hydrogen bonds can be the major change in the crystalline structures, leading to the reduction of the thermal conductivity of PE by a half after the α-to-γ phase transition.