Preparation and characterization of double-MF shell microPCMs used in building materials

A kind of double-shell heat energy storage microcapsule was prepared used melamine formaldehyde (MF) resin as shell material, and the properties of the microcapsules were investigated. A phase change material, with melt point of 24 degrees C and phase transition heat of 225.5J/g, was used as core. The microcapsules would be used in indoor walls to regulate the temperature and save energy. The surface morphological structure was examined by means of scanning electron microscopy. The strength of the shell was evaluated through observing the surface change after pressure by means of scanning electron microscopy. The average diameter of the microcapsules was 5 mu m similar to 10 mu m. Diameter of 1 mu m similar to 5 mu m could also be obtained by using different stirring speeds. The globular surface was smooth and compact. The thickness was 0.5 mu m similar to 1 mu m. Also, the melting point of the microcapsules was 24.7 degrees C, nearly equal to the pure phase change material. The DSC results make clear that the polymer shell of the microcapsules does not influence the properties of the phase change material. It was also found that the avoiding penetration property of the double-shell microcapsules was better than that of single shell, and the average diameter of 5 mu m was better than 1 mu m. With the increase of ratio of the core material, the compactability decreased, and the shell thickness decreased. The mass ratio of core and shell was 3 : 1 to ensure that the microcapsules had good heat storage function. The measuring test showed that the microcapsules did not rupture at a pressure of 1.96 X 10(5) Pa. (C) 2005 Wiley Periodicals, Inc.