Design and mechanism analysis of decanoic acid-palmitic acid/SiO2@TiO2 phase change microcapsules based on RBF model

Abstract

The decanoic acid-palmitic acid/SiO2@TiO2 phase change microcapsule (D-P-SiO2@TiO2 PCM) not only has the temperature regulation function, also it can degrade pollutants though photocatalysis and control humidity. In order to optimize the photocatalytic-humidity performance of the D-P-SiO2@TiO2 PCM, the uniform test was designed and RBF model was used to optimize the preparation parameters. The degradation rate of gaseous formaldehyde by the optimized D-P-SiO2@TiO2 PCM was 69.57% after 6 h and the moisture content was 0.0923–0.0940 g·g− 1 at 43.16–75.29% RH. The comparison result between model optimization and the experiment sample that prepared by using the optimized parameters showed that the theoretical photocatalytic-humidity performance target value was 2.0502, and the tested target value was 2.0757. The error of the two was only 1.24%, and both were bigger than the best value of uniform experimental. Micro-structure analysis of the optimized D-P-SiO2@TiO2 PCM showed that it had uniform spherical structure, the particle size was about 200 nm, the phase transition temperature range was between 16.97 ~ 28.94 oC, within the comfort range of human body. The optimized D-P-SiO2@TiO2 PCM had high specific surface area and multiple pore structure, so it can regulate air humidity. Further analysis of the preparation mechanism of D-P-SiO2@TiO2 PCM showed that the super-water system and acidic conditions were favorable for the hydrolysis of tetraethyl silicate to generate SiO2 with 3D short chain structure, so as to effectively encapsulate the decanoic acid-palmitic acid compound phase change material. The pH controlled 2 ~ 3 was necessary for hydrolyzing of tetraethyl titanate into anatase phase TiO2. The above is the basis conditions for preparing D-P-SiO2@TiO2 PCM with photocatalytic-humidity performance.