pH值对正十八烷微胶囊合成与性能的影响

pH值对正十八烷微胶囊合成与性能的影响;微胶囊;相变材料;正十八烷

Effects of pH on Synthesis and Properties of Microencapsulated n-Octadecane

The effects of pH on the emulsion and prepolymer solution stability,morphologies and(properties) of the microcapsules were studied in the fabrication of microencapsulated n-octadecane by in-situ polymerization of melamine-formaldehyde.The pH value in the range of 6.5~9.0 does not significantly affect the stability of the emulsion.The prepolymer of melamine-formaldehyde is easy to polymerize in the acid(solution),however,it is hard to polymerize in the alkaline solution.The separation time of the prepolymer solution is prolonged with the increase of pH value,and shortened with the increase of temperature.The(residual) formaldehyde(exists) in the melamine-formaldehyde polymer when the pH value is low.The microcapsules are perfect sphere and are dispersed well when the pH value of polymerization system is 4~5.Both the enthalpy and thermal(stable) temperature of the microcapsules increase with the rise of pH value;however,the pH value in the range of 4~5 is preferable due to the dispersity and reaction period of the microcapsules.