Shape Stability of Polyethylene Glycol/Acetylene Black Phase Change Composites for Latent Heat Storage

Abstract

Sufficient shape stability is essential for a high-performance phase change material (PCM). Although significant advances have been made to develop form-stable composites, technical development in the field of polymer-based PCMs is currently limited by an incomplete understanding of the shape stability. Form-stable polyethylene glycol/acetylene black (PEG/AB) PCMs containing PEGs with different average molecular weights have been obtained by melt mixing to investigate the shape stability of the PEG/AB composites. It was found that the phase change behaviors of the PEG/AB composites were not only attributed to the interactions between the AB and PEG, but also to the intermolecular interactions of the PEG chains, depending on the varying molecular weights of the PEGs. Physically crosslinked structure with temporary junctions was formed through hydrogen bonding, capillary, surface tension forces, intermolecular friction, and macromolecular entanglement, which contributed to the constrained chain motion and thus the solid-solid phase change behavior of the PEG/AB composites. The physically crosslinked structure was more stable with longer length of the PEG molecular chains, resulting in higher critical impregnated contents of the PEG into the AB and thus improved latent heat.

Physical Properties of an Eco-Sustainable, Form-Stable Phase Change Material Included in Aerial-Lime-Based Mortar Intended for Different Climates

“…The leakage behavior of the PCM composite materials (LS/PEG800 and LS/PEG1000) was investigated, as this was previously reported as a weakness in the use of low molecular weight PEGs to produce PCM [ 36 , 37 ]. Since no standardized test is currently available to measure this characteristic, a procedure reported in [ 36 ] was employed.…”

“…The leakage behavior of the PCM composite materials (LS/PEG800 and LS/PEG1000) was investigated, as this was previously reported as a weakness in the use of low molecular weight PEGs to produce PCM [ 36 , 37 ]. Since no standardized test is currently available to measure this characteristic, a procedure reported in [ 36 ] was employed. In accordance with this method, 5 g of LS/PEG800 granules were placed on a preweighed filter paper, which was then placed in an oven (Binder FD 240, Waltham, Massachusetts, US) at a temperature close to the melting temperature of PEG 800 (30–35 °C); this was selected by taking into account the melting peak closure, as previously measured by the DSC.…”

“…In most of the papers reporting the use of PEGs to produce PCMs, polyethylene glycol polymers with molecular weight not lower than 1000 have been employed. To the best of our knowledge, only a few works proposed PEGs with lower grades (e.g., PEG 800 [ 19 , 30 , 35 ] and PEG 600 [ 36 , 37 ]) to manufacture PCMs. However, leakage issues in the melting state limit the use of such PEGs as a form-stable PCM in real-world applications.…”

“…However, leakage issues in the melting state limit the use of such PEGs as a form-stable PCM in real-world applications. Consequently, these form-stable PCMs have very rarely been embedded in mortar; generally, they have been thermally characterized and proposed as effective PCMs for use in different TES applications [ 30 , 35 , 36 , 37 ].…”

Environmentally Efficient 316L Stainless Steel Feedstocks for Powder Injection Molding

“…The first loss of 0.9 wt % is attributed to PW and SA, which have been reported to appear between 140 and 275 • C (PW) [24,25], and from 150 to 300 • C (SA) [26,27]. The second loss of 2.05 wt % means mainly removal of AW [17,28], and the last weight drop of 0.96 wt % is linked to the evaporation of the rest of the AW and remains of the PEG (both PEG 4000 and PEG 6000 have been reported to start to degrade between 350 • C and 430 • C [29]). This three-step process is gradual, which is desirable for shape retention and prevention of cracks.…”