Microencapsulation of n-hexadecanol by in situ polymerization of melamine-formaldehyde resin in emulsion stabilized by styrene-maleic anhydride copolymer

Microcapsules with high thermal energy storage density were synthesized by in situ polymerization using melamine-formaldehyde resin as shell and n-hexadecanol as core. Styrene-maleic anhydride (SMA) copolymer was synthesized by solution polymerization and hydrolyzed by NaOH to enhance its water solubility. This negatively charged SMA molecular copolymer self-assembles on the surface of n-hexadecanol droplets and facilitates the precipitation of positively charged melamine-formaldehyde prepolymer onto the droplet surface electrostatically. The morphology, chemical structure, composition, and thermal properties were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, and gas chromatography, respectively. The results show that the obtained microencapsulated phase-change material (MePCM) dispersed individually with a spherical shape. Amount of emulsifier, ratio of shell-core material, and pH value of solution have a significant effect on the microencapsulation. Under optimum condition of 8% SMA to core material, 3.3:10 of shell-core material in feed, and polymerization under pH 4.0, spherical n-hexadecanol MePCMs with core content of 79.1% and melting enthalpy of 171Jg^-1 at around 51°C were prepared. In situ polymerization based on SMA-stabilized emulsion opens up a route to prepare a variety of microcapsules with aliphatic alcohol as core material.