A Relationship Between the Heat of Vaporization, Surface Tension, and the Solubility Parameters, Which Includes the Ratio of the Coordination Numbers, Based on Stefan's Rule

Hansen Solubility Parameters for Directly Dealing with Surface and Interfacial Phenomena

To integrate surface and interfacial properties and phenomena into the Hansen solubility parameter (HSP) framework, we propose an equation for estimating both surface tension/energy for liquids and solids as well as interfacial tension/energy. The contact angles of probe liquids on various polymers estimated using the proposed equation based on bulk HSPs (derived from bulk properties such as solubility or swelling, and not on surface properties) are compared with those measured using the sessile drop method. It is found that their correlations are sufficient for predicting wettability in practical use. All the respective tension and energy correlations are reasonably good, confirming the predictive power of the proposed equation for all values of liquid surface tension, solid surface energy, and interfacial tension. The unification of surface and interfacial properties and phenomena with HSPs (derived from bulk properties) enables us to estimate the surface properties from bulk properties and vice versa. The huge database of HSPs is now applicable to not only bulk phenomena but also surface and interfacial phenomena. Furthermore, complex processes or systems composed of multiple constituents and phases can be understood and designed using the modified HSP framework.

Preparation of n-Alkane/Polycaprolactone Phase-Change Microcapsules via Single Nozzle Electro-Spraying: Characterization on Their Formation, Structures and Properties

The phase change microcapsule (mPCM) is one of the primary candidates in the fields of energy storage and thermal regulation. In this study, electro-spraying, as a green, high-efficiency electrohydrodynamic atomization technology, is applied to the microencapsulation of two phase change materials (PCM) (n-hexadecane and n-eicosane) with three loading contents (30%, 50%, and 70% by weight) in a polycaprolactone matrix. Ethyl acetate (EA) and chloroform (Chl) were chosen as solvents to prepare the working solutions. The objective of this study is to clarify the microencapsulation process during electro-spraying and to optimize the structure and properties of the electro-sprayed mPCM. The structures, morphologies, and thermal properties of the mPCM were characterized by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and fourier transform infrared spectroscopy (FT-IR). Electro-sprayed spherical and non-porous mPCM have been successfully prepared. The mean diameter and the particle size distribution depend mainly on the choice of the n-alkane, as well as the solvent used to prepare the working solutions. Meanwhile, the structure formation of electro-sprayed mPCM and the loading content of PCM were mainly influenced by the evaporation of the solvent and the phase separation between PCM and poly(caprolactone) (PCL) matrix. During the shell formation or PCL solidification, the control of the PCM leaching out of the matrix allows improving the loading content. Finally, based on a high latent heat and simple formation process, the electro-spraying route of PCM is a green, non-toxic, and high-efficiency direction for energy storage and heat regulation.