New boron-containing microcapsule for energy storage with upgraded flame retardant properties

This study includes encapsulation of a phase change material (PCM), n-octadecane, in boron functionalized polyurethane (PU) shell by interfacial polycondensation method without using cross-linker. Boron is expected to impart flame retardancy to PU based shells. The fact that the boric acid used in the study is abundant and cheap in our country makes the study economically advantageous. This work is noteworthy because it is the only microcapsule study using boric acid rather than ours. In this context, boric acid-containing capsule (TB) and ethylene glycol-containing capsule (T) were produced and compared in terms of latent enthalpy storage capacity, flame retardancy, and some other common specific properties. Fourier transform infrared (FT-IR) spectrophotometer, differential scanning calorimeter (DSC), thermal gravimetric (TG) analysis, bomb calorimeter analysis, particle size distribution (PSD) analysis and scanning electron microscopy (SEM) were utilized for characterization and purification of thermal resistance of produced microcapsules. The average particle diameter of produced microcapsules is between 13.4-20.0 µm and encapsulation efficiency is also between 28.4 % (68.6 Jg-1) -39.6 % (96.0 Jg-1). Limited oxygen index (LOI) values of TB and T are 20.2 and 18.7. Calorie releases for capsules are 34.6 kJg-1 and 16.7 kJg-1 respectively. N-octadecane is an organic compound and has a high vapor pressure especially at high temperatures. It was clearly seen in this study that its evaporation was prohibited up to 180 ℃ in PU-boron based shell by encapsulation.