Green Production of Lauric Acid/Stearic Acid@Sodium Alginate/Copper (II) Oxide Photothermal Microcapsule by Pickering Emulsion Complex Coacervation Method for The Design of Multifunctional Cotton Fabrics with Thermoregulation and UV Protection

This study presents the production of photothermal composite capsules using a newly developed method and their application to cotton fabric for the design of a fabric that exhibits both thermoregulation and UV protection properties. In this study, an environmentally friendly approach was adopted in the production of photothermal capsules and unlike the existing methods in the literature, the Pickering emulsion system was integrated into the complex coacervation method. The phase change material, a eutectic mixture of lauric acid and stearic acid, was encapsulated within a sodium alginate/copper (II) oxide (CuO) wall in three different ratios (1/0.5, 1/1 and 1/1.5). In microencapsulation, CuO nanoparticles were used as photothermal material both as Pickering stabilizers and wall structure polymer. Microcapsules with spherical morphology were found to store heat in the range of 99.1–118.7 J/g and have good thermal reliability. The photothermal performance of the capsules improved in direct proportion to the amount of CuO nanoparticles in the wall structure and the highest photothermal efficiency value with 96.97% efficiency was obtained in capsules with 1/1.5 S/CuO wall structure. Microcapsules with 1/1.5 S/CuO wall structure were fixed to cotton fabric at two different concentrations via the exhaustion method. The fabrics exhibited photothermal properties, reaching temperatures 5 °C higher than the untreated fabric during the same time period. The S/CuO walled microcapsules significantly improved the thermal conductivity of the fabrics. Besides, fabrics exhibited good UV protection with a 15 UPF value. In contrast, the bending rigidity and tear strength of the fabric were affected by the capsule application.