Preparation, characterization, and thermal properties of microencapsulated palmitic acid with ethyl cellulose shell as phase change material impregnated wood

Abstract

In this work, palmitic acid (PA) was encapsulated in ethyl cellulose (EC) by emulsification–solvent evaporation method. The morphology and particle size of the PCMs were examined using SEM and particle size analysis, and similar particle size (80 % is between 0 and 100 μm) was observed. The crystal phase and chemical structure of microencapsulated phase change materials (MPCM) were measured by XRD (X-ray diffractometer) and FTIR (Fourier transformation infrared spectroscope), observed that there is no chemical bond between EC and PA, but a physical bond. TGA (thermogravimetric analyzer) and DSC (differential scanning calorimeter) analysis were used to thermal properties including phase change temperature, enthalpy, thermal stability, the thermal conductivity of MPCM, and MPCMW. The results show that MPCM possesses excellent thermal stability at working temperature, and the most satisfying samples are MPCM2,3 with phase change enthalpy of 98.85 J/g, 135.1 J/g, and phase change temperature of 58.29 °C and 60.76 °C (medium-temperature zone (buildings fields)), respectively. Microencapsulation of PA with EC is one of the most important achievements of the study. Poplar (Populus euramericana) wood samples were impregnated with MPCM using a vacuum-pressure process (MPCMW). After impregnation, approximately 15 % weight gain was obtained in wood samples. It was determined that there was no change in the chemical structure and crystallinity ratios of the impregnated samples by FTIR and XRD, and thermal decomposition took place in two stages by TGA analysis. MPCMW samples started to decompose at 200 °C. Latent heat storage of 30.8–82.62 J/g between 59.70 and 61.73 °C was measured for MPCMW. MPCMW had great durability with latent heat of 40–50 J/g after 50 heating-cooling cycles. The thermal conductivity enhancements are about 40 % higher than the reported corresponding values for poplar wood. Using the microcapsule-impregnated wood, a new method for developing and utilizing high-value poplar wood in the energy storage is provided.