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Pré-Publication, Document De Travail Année : 2021

Thermal characterization of polyethylene glycol 600 in liquid, solid phases and through the phase transition

Résumé

The polyethylene glycol, a long chain polymer, is characterized by experimental means in both solid and liquid phases. Main thermal properties inherent to the phase transition are also provided in this study. More specifically, we focus on a low molecular weight PEG, named PEG 600, whose average molecular mass is 570-630 g mol$^{-1}$ and melting temperature transition is about 10-20°C. The phase change does not occur clearly at a given temperature but rather over a range of temperatures highlighting a complex material. As a first approach, this paper gives thermal properties of the PEG 600 either for completing the literature in which only few properties are provided or for confirming existing data. Several methodologies have been developed and calibrated in order to obtain in both phases, the density as well as the thermal conductivity. Measurements of the thermal conductivity are carried out using two different methods, i.e. a stationary hot tube device and a transient hot needle one. For the density two different devices are employed for each phase: a densimeter for the liquid phase and a pycnometer for the solid phase. Our results allow to propose a temperature $T$ dependent fit of density in the liquid phase $\rho(T)=-0.8164 \, T+1142.211$ kg.m$^{-3}$. The relative density variation from the liquid to solid phase is significant as it reaches about 35\%, meaning also that the volume shrinkage is quite large. Differential Scanning Calorimetry DSC has been used for measuring the heat capacity of solid and liquid phase as well as the effective one at the transition states. Several protocols have been tested and compared all together in order to characterize intrinsic properties. The latent heat of fusion/solidification has been estimated through the effective heat capacity obtained with heating/cooling protocols. The latent heat converges to one value $L \approx 130$kJ/kg, whatever the protocol used. Undercooling effects are decreased by performing DSC with slow temperature variations. Finally, we have observed several exothermic peaks during the freezing process highlighting some successive reorganizations within the internal structure of PEG.
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Dates et versions

hal-03516867 , version 1 (07-01-2022)
hal-03516867 , version 2 (21-03-2022)
hal-03516867 , version 3 (13-05-2022)
hal-03516867 , version 4 (21-07-2022)
hal-03516867 , version 5 (29-09-2022)

Identifiants

  • HAL Id : hal-03516867 , version 3

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Justine Noel, Yves Jannot, Christel Métivier, Nicolò R Sgreva. Thermal characterization of polyethylene glycol 600 in liquid, solid phases and through the phase transition. 2021. ⟨hal-03516867v3⟩
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