<p>Ceramsite is often used as a carrier for phase change materials due to its high strength and porous properties. However, when it is compounded with different polar phase change materials, the prepared phase change aggregates show significant differences in performance, and its mechanism of action has not yet been clarified, which needs to be studied in depth. In this paper, phase change aggregates were prepared by using ceramsite to adsorb polar phase change material PEG and nonpolar phase change material paraffin, respectively. The adsorption test revealed that the main driving force for the adsorption of PCMs by ceramsite under atmospheric pressure is capillary force, and the polarity of PCMs affects the adsorption capacity of ceramsite, but this effect can be neglected under negative pressure (− 1&#xa0;MPa). DSC test showed that the effect of ceramsite on the phase change properties of PEG was more significant compared to paraffin, and the crystallization rate of PEG/ceramsite was only 86.32%. By weakening the hydrogen bonding between PEG and ceramsite, it was found that hydrogen bonding is the main reason for the large changes in the phase transition properties of PEG. On the one hand, hydrogen bonding provides nucleation sites for PEG to reduce the degree of supercooling, and on the other hand, hydrogen bonding restricts the normal crystallization of PEG molecules. After quantitatively analyzing the leakage process, it was found that the polarity relationship between ceramsite and PCMs determine the leakage rate by regulating the contact angle at the interface between the two. It was calculated that the critical pore size for leakage of PEG/ceramsite was greater than the vast majority of the pore size of ceramsite. The surface tension generated in the pore size of the ceramsite is sufficient to counteract the effect of PEG gravity, thereby ensuring the stability of the phase change aggregates in their definitive form.</p>