Effect of alkyltriethoxysilane on the performance of sodium silicate-based silica shell phase change microcapsules

Preparing silica/paraffin phase-change microcapsules using sodium silicate as a substrate is an inexpensive and nontoxic process. However, the sodium silicate is easily self-polymerized during the preparation of microcapsules; this results in low encapsulation ratio and poor toughness. In this study, in order to obtain better controllability and encapsulation performance, we prepared silica-paraffin phase change microcapsules by introducing different silane coupling agents and Na2SiO3 co-condensation. The micromorphology and phase-change characteristics of microcapsules were investigated using Scanning electron microscope, transmission electron microscope, thermogravimetric analysis, and differential scanning calorimetry. The results demonstrated that the melting enthalpy of the microcapsules modified by propyltriethoxysilane reached 136.1 J g−1, and its encapsulation ratio was 92.59%, which was 35.93% higher than that of the unmodified microcapsules. Moreover, the melt permeability of microcapsules modified by methyltriethoxysilane can be as low as 12.35% under pressure (5 MPa, 30 s), which was 20.53% less than that of the unmodified microcapsules.