Low-temperature synthesized aluminosilicate glasses Part IV Modulated DSC study on the effect of particle size of metakaolinite on the production of inorganic polymer glasses

The effect of the particle size of metakaolinite on the reaction kinetics of low-temperature synthesized inorganic polymer glasses is studied. The heat capacity of the material during isothermal cure is measured by Modulated DSC (MDSC). This signal can be followed quantitatively during the complete course of the reaction, whereas the heat flow signal is sometimes too small for quantitative interpretations. A characteristic time for the reaction, defined as onset of vitrification, is also measured with Dynamic Mechanical Analysis (DMA). The DMA and MDSC results show that the reaction rate increases with decreasing particle size of metakaolinite, at least till a particle size of about 2 μm. It can be concluded that the first step of the reaction, breaking down the metakaolinite grains, occurs at the surface of the particles. The second step is the building of a network starting from the reaction products of the former reaction.