Microencapsulation of a cooling agent by interfacial polymerization: Influence of the parameters of encapsulation on poly(urethane–urea) microparticles characteristics

A series of polyurea–urethane microparticles containing xylitol were synthesized by interfacial polymerization from reaction between diphenyl methylene diisocyanate (MDI) and xylitol. This research was conducted to clarify the influence of different parameters on the encapsulation process, i.e. during the emulsion formation step and during the shell formation using contact angle measurement, Fourier-transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analyses. By carefully analyzing the influencing factors stirring rate and feeding weight ratio of core/shell monomers, the optimum synthetic conditions were found out. The results show that core/shell weight ratio influences not only the shell formation mechanism but also the mean diameter, microcapsule morphology, the encapsulation yield and the xylitol content. Thus, the choice of a core/shell weight ratio of 77.0–23.0 is the most suitable to obtain high encapsulation yield and xylitol loading content.

Excessive agglomeration of tiny polyurea–urethane particles occurs when selecting lower or higher core–shell weight ratio, and microparticles are easily deformed due to the thinner wall shell.Figure optionsDownload high-quality image (298 K)Download as PowerPoint slideResearch highlights▶ The stirring rate of the emulsion step influences the size and the loading content of the particles. ▶ An increase of stirring rate is correlated to a decrease of urea linkages. ▶ The encapsulation yield values are correlated to the urea linkages formed. ▶ The formation of urea linkages enhances the stability of the polymer shell. ▶ The hydrophilic microparticles nature can be modulated by the MDI amount introduced.