Development and characterization of paraffin-based shape stabilized energy storage materials

The passive nature of energy storage through phase transition makes phase change materials (PCMs) a reliable choice for many applications. Shape-stabilized phase change materials (PCMs) mix liquid PCM with a molten polymer to create a material in which the PCM is fully contained even above the melt temperature of the PCM. Since the energy storage in the material will be a function of the amount of PCM, it is desirable to shape stabilize the material with as little polymer as possible. It is also important to understand the physical strength of these materials if they are to be used without a containment structure. Therefore, this study experimentally characterizes the structural and thermal properties of SS-PCM, identifies the effects of changing polymer loading level, provides guideline to determine at what point the material becomes shape-stabilized, and determines the heating and cooling curves. Based on these tests, it can be concluded that a sample of PCM can be considered to be shape-stabilized when the loading level of polymer creates a sample with structural integrity above the melting point, with geometric stability including elimination of contraction upon solidification and a sample with no circulation of the PCM during the melt phase, as well as full containment of the melt. For the samples investigated here, shape stabilization occurs in paraffin/HDPE mixtures above 25–30% HDPE.

► Shape stabilized phase change material made with paraffin and 10–50% HDPE.
► Determine effects of polymer loading level on shape stabilized phase change material properties.
► Samples above 25–30% HDPE exhibited structural strength above the melt point.
► Samples above 10% HDPE exhibit significant reduction of the ullage space.
► Samples below 25% HDPE exhibit paraffin circulation at high temperatures.