High-intensity ultrasound assisted manufacturing of melamine-urea-formaldehyde/paraffin nanocapsules

The average diameters of encapsulated phase change materials (PCMs) affect their physical properties. In this study, the effects of the main emulsification variables (ultrasound time and output power of ultrasonic treatment) were explored and then melamine-urea-formaldehyde (MUF)/paraffin nanocapsules were obtained via an in-situ polymerization method. The influences of these variables on the stability of the MUF/paraffin nanoemulsions and the appearances, mean droplet diameter and thermos-physical properties of MUF/paraffin nanocapsules were investigated. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), and differential scanning calorimetry (DSC) were employed to characterize the morphologies, size distributions, and thermal stabilities of MUF/paraffin nanocapsules, respectively. The characterization results showed that the more stable nanoemulsion could be formed after ultrasonic treatment for 15 min under the output power at 600 W compared with mechanical stirring emulsification. When the ultrasonic output power was 600 W, the MUF/paraffin nanocapsules achieved the highest encapsulation efficiency (35.8%) and encapsulated paraffin in the MUF shell under the output power of 600 W was more than that obtained under other ultrasonic output power values. This study verified that the ultrasound-assisted emulsification process could be used to fabricate stable MUF/paraffin nanocapsules.