Design of double-layered microcapsule shell by electrospraying route for functional coating of fibers and textile

Phase change materials (PCMs) can store or spontaneously release a large amount of latent heat during their phase transitions induced by surrounding temperature variations. They are considered the leading candidates for thermal energy storage and meet the increasing demand for thermal management, and are also used in textiles to improve thermal comfort. In recent years, electrospraying has been widely used to manufacture microparticles and microcapsules. When textiles are placed on the collector, the functional coating of the textiles by the electrosprayed microcapsules is achieved during the electrospraying process. This work aims at designing an appropriate electrospray method to trap the MPCs in microcapsules with a double shell layer. Poly(lactic acid) and polycaprolactone have been selected as fusible inner and outer shells for surface functionalization of textiles during a post-treatment by temperature rise.Poly(caprolactone) (PCL) microparticles were produced by electrospraying using five solvents (ethyl acetate, acetone, anisole, glacial acetic acid, and chloroform) at different concentrations of PCL and adjusting the operating parameters. The effects of solution properties (surface tension, electrical conductivity, viscosity, and vapor pressure) and operating parameters (flow rate, working distance, and applied voltage) on the formation of electrosprayed particles were clarified.Two n-alkanes (n-hexadecane and n-eicosane) with three filler contents (30%, 50%, and 70% by weight) were successfully encapsulated in a polycaprolactone matrix by single-nozzle electrospraying with ethyl acetate (EA) and chloroform (Chl) as solvents. The effects of n-alkane phase state, n-alkane additions, and solvent selection on the electro-microencapsulation process, and the structure, morphology, and properties of the resulting mMCPs were analyzed. In order to improve the efficiency of the encapsulation, a coaxial system was also used. A complete comparison between single-nozzle and coaxial electrospray in the encapsulation of MCPs, focusing on the structures, morphologies, and thermal properties of the corresponding microcapsules, was performed. Due to certain limitations related to LCP, polylactic acid was chosen as an alternative shell matrix to achieve the microencapsulation of PCMs. The effects of PLA concentration and n-hexadecane filler content on the structures and properties of the resulting mMCPs were analyzed. Finally, based on this work, the double membrane microcapsules were fabricated by coaxial nozzle electrospraying. In the meantime, in order to optimize the structure, morphology, and thermal properties of the final n-hexadecane / PLA/PCL microcapsules and to better realize the functional coating of textiles, the effects of the different additions of n-hexadecane, of the different weight ratios between PCL and PLA on the structures, morphologies, and properties of the resulting mMCPs were studied in detail. Electrosprayed microcapsules with a double-layer envelope will offer great potential and advantages for the manufacture of thermally controlled textiles and a new orientation for the fields of energy storage and thermal management.