Preparation and characterization of novel MicroPCMs (microencapsulated phase-change materials) with hybrid shells via the polymerization of two alkoxy silanes

MicroPCMs (microencapsulated phase-change materials) were successfully synthesized using MPS (3-(trimethoxysilyl) propyl methacrylate) and VTMS (vinyltrimethoxysilane) as raw materials for hybrid shells, and n-octadecane as core materials. DSC (differential scanning calorimeter) results show that two types of crystals form in core materials of all MicroPCMs during crystallization. The weight ratio of MPS-VTMS, and pH values play significant roles on the performance of final product: n-Octadecane content of MicroPCMs increases from 58.7 wt.% to 76.0 wt.% and their thermal degradation temperature (2 wt.% weight loss) increases from 182.6 °C to 188.9 °C with the weight ratio of MPS-VTMS decreasing from 8:0 to 2:6 in neutral synthesis systems. However, the encapsulation of n-octadecane failed when only using VTMS as hybrid shell precursor; When the weight ratio of MPS-VTMS is fixed to 2:6, the encapsulation efficiency decreases in acidic or basic synthesis systems. The optimized final product, i.e., MicroPCMs obtained with the weight ratio of MPS-VTMS equaling to 2:6 in neutral conditions, display a best thermal properties with highest melting and crystallization latent heat of 166.74 J g−1 and 169.35 J g−1, and the n-octadecane content decreases only by 7.0 wt.% and 10.8 wt.% after thermal treatment and thermal cycling test, respectively.