Preparation and optimization of graphene oxide on thermal conductivity of melamine urea-formaldehyde@n-hexadecane phase change microcapsules (MEPCMs)

Microencapsulated phase change materials (MEPCMs) effectively settle drawbacks of phase change materials, such as leakage, and are widely used in realms of intelligent temperature control fibers and textiles, building energy conservation, and thermal energy storage systems. Based on the in-situ polymerization method, melamine urea-formaldehyde (MUF)@n-hexadecane MEPCMs are fabricated and modified by adding graphene oxide (GO) to the shell to enhance the thermal conductivity. Characteristics of MEPCMs are demonstrated with field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Hot Disk constant analyzer. The GO/MUF@n-hexadecane MEPCMs possess satisfactory thermal storage performance and thermal stability. The addition of GO has little influence on the micromorphology and chemical structure of MEPCMs. As GO content increases, the thermal conductivity of GO-modified MEPCMs has been significantly improved. Modified MEPCMs with 0.1wt% GO possess average latent heat value and highest encapsulation efficiency at 217.2 J/g and 95%, respectively. Those with 0.3wt% GO have integrated microstructure and highest thermal conductivity coefficient at 0.1554W/(m·K), 89.05% higher than unmodified MEPCMs. Modified MEPCMs mainly undergo a two-step degradation process, indicating that the GO-modified MUF shell plays a certain role in blocking the thermal decomposition of the core.