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

Abstract

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.

Influence of a Coaxial Electrospraying System on the n-Hexadecane/Polycaprolactone Phase Change Microcapsules Properties

“…One of the main interests in the use of a coaxial nozzle system to encapsulate phase change material is related to the increase in the efficiency of the system. Thus, with regard to our previous study [52], it is noticed that the encapsulation efficiency as well as the loading content of n-hexadecane in mPCMs depend on the type of nozzle and the solutions used. The encapsulation efficiency and loading content of n-hexadecane in mPCM obtained from a coaxial nozzle electrospraying system were found to be higher than with a single nozzle one at 10 w/v % PCL solution.…”

“…Therefore, it leads to the obtention of a mono-dispersed distribution, especially when the core to shell proportion is about 30:70. For single nozzle electrospraying, microcapsules with a mono-disperse distribution are obtained regardless of the amount of n-hexadecane used [52]. Indeed, the presence of the solvent increases the electrical conductivity, which leads to better stabilization of the Taylor cone and facilitates the breaking process.…”

“…For a feed ratio of 2:1 between the core and shell liquids, the encapsulation efficiency was about 85%, and the loading content of PCM in the microcapsules having a mean diameter from 1 to 2 µm was about 56%, corresponding to a phase change enthalpy about 122 J.g −1 . Recently, Zhang et al studied the encapsulation of n-alkane in a polycaprolactone shell using a single nozzle process [52]. Depending on the formulation of their solution, the process was carried out with an encapsulation efficiency of 70%-84%, and the resulting mPCM had an enthalpy of phase change of about 99-117 J.g −1 .…”

“…The structures, morphologies, and thermal properties of the obtained microcapsules were characterized by scanning electron and optical microscopies (SEM and OM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The results were also compared to this obtained from a single electrospraying nozzle [52].…”

Study on the Influencing Factors of the Atomization Rate in a Piezoceramic Vibrating Mesh Atomizer

“…Piezoelectric injection and atomization devices are widely applied in inhalation therapy [1], dust collection [2], preparation of microcapsule [3], printed circuits [4], precise surface coating [5], 3D prototyping [6], spray drying [7], spray cooling [8], inkjet printing [9], and many other fields. Specifically, the micron-sized droplet technique, with the characteristics of stable injection and full dispersion, constitutes an important development direction in these fields [10].…”