TiO2-UF@Tet microcapsules were prepared using two-step method

where the advantages of the organic shell layer (toughness and leakage prevention) and the inorganic shell layer (flame retardant

mechanical strength and good heat conduction) are combined. The effect of the mass fractions of TiO2 on the performance of composite shell phase change microcapsules were investigated. The morphology

chemical composition

and thermodynamic properties of the phase change microcapsules were investigated using biological microscopy

scanning electron microscopy (SEM)

Fourier transform infrared spectroscopy (FT-IR)

energy dispersive spectroscopy (EDS)

differential scanning calorimeter (DSC)

and thermogravimetric analysis (TG). The experimental results show that the microcapsules formed by TiO2 and UF have a good composite shell structure by two-step method. The phase transition temperature of the microcapsules shifted towards lower temperatures

the latent heat of phase transition decreased

and the thermal conductivity increased continuously with the increase of the mass fraction of TiO2. The prepared microcapsules have smooth surfaces

uniform particle size distribution

and an average particle size of approximately 2.0 μm. The phase transition temperature and latent heat of the optimal composition are 3.1℃ and 168.5 J/g

respectively

with a coating rate and coating efficiency of 71.64% and 69.08%

respectively. After 100 heating cycles

the phase transition temperature remains stable

and the microstructure is good. It is suitable for cold storage of air conditioning systems.