Synthesis and characterization of microencapsulated n-octadecane with hybrid shells containing 3-(trimethoxysilyl) propyl methacrylate and methyl methacrylate

Abstract

Microencapsulated phase-change materials (MicroPCMs) were successfully synthesized using 3-(trimethoxysilyl) propyl methacrylate (MPS) and methyl methacrylate (MMA) as raw materials for hybrid shells, and n-octadecane as core materials. The influence of mass ratio of MMA–MPS, hydrolysis of MPS and polymerization temperature on the performance of MicroPCMs are investigated. Adding the amount of MPS gives a growth of more sub-microscale particles on the surface of MicroPCMs, and the average particle sizes are close. Increasing the amount of MPS leads to an increase in the char yields, which indicates that there are more inorganic Si–O–Si network components in the shell materials. The pre-hydrolysis of MPS has the negligible influence on the average particle sizes of the MicroPCMs. The neutral or base-catalyzed condition can result in an increase in the amount of sub-microscale particles from the surface of MicroPCMs. The base-catalyzed condition can produce a decrease in the content of n-octadecane in the MicroPCMs, while the neutral can provide an increase. The neutral or base-catalyzed condition can increase the char yields at 550?°C, while the acidic condition not. Lowering the polymerization temperature can form finer particle sizes for the MicroPCMs and make more β-form n-octadecane crystals to transform to α-form crystals in the MicroPCMs. In addition, decreasing the polymerization temperature can add the percentage of the content of n-octadecane. MicroPCM with the polymerization temperature 70?°C has the crystallization enthalpy of 158.01?J?g^?1 and melting enthalpy of 158.62?J?g^?1, with the encapsulation efficiency ~73.0?mass%.