Synthesis and properties of microencapsulated phase change materials with melamine-urea-formaldehyde resin shell via nano-silica stabilized Pickering emulsion

Microencapsulated phase change materials (MPCMs) with melamine–urea–formaldehyde (MUF) shell and n-tetradecane core were synthesized via in-situ polymerization. Hydrophobically modified nano-silica was employed as emulsifiers of Pickering emulsion and reinforcing nanofillers of MUF shell. The influence of encapsulation parameters (nano-silica concentration, core/shell ratio, synthesis time, and emulsification speed) on the morphology, particle size, and enthalpy characteristics were investigated. The chemical structure, morphology, and thermal performance of MPCMs were characterized by FTIR, SEM, DSC, and TGA technologies. The nano-silica concentration of 10%–12.5%, core/shell ratio of 1:1.5, emulsification speed of 7000–8000 rpm, and synthesis time of 180 min are recommended for MPCM synthesis. The synthesized MPCMs at optimum condition exhibited a spherical morphology with average diameter of 4–5 μm, melting and solidifying enthalpy of 124.9 and 135.3 J/g, an encapsulation efficiency of 56%, a thermal conductivity of 0.1035 W/(m·K), and thermal stability up to 200 °C, indicating good potential in practical engineering applications.