The functionalization of film materials for grafting WPU with polystyrene hollow microspheres

Surface coating expresses the most appealing quality of a product. Multifunctional waterborne polyurethane (WPU) coatings with thermal insulation, matting, UV resistance and hydrophobicity are one of the targets of advanced materials manufacturing. In this study, polymer hollow microspheres with polyhydroxy groups on the surface, called HM-OH, were prepared by emulsion polymerization. Through TEM and SEM observations, it was confirmed that the HM-OH has a cavity (approximately 207 nm in diameter) with an average diameter of 726 nm. The relative content of the hydroxyl group on its surface is 9.1 %, and it has good dispersibility and thermal stability. A multifunctional low-gloss WPU nanocoating was prepared by grafting onto HM-OH, called WPU-g-HM. The emulsion stability test showed that WPU-g-HM basically solved the problem of blending incompatibility between HM and WPU, and the tensile strength and elastic modulus of WPU-g-HM reached their best values when the amount of HM-OH was 2.5 %. UV–vis testing showed that the HM-OH made the prepared nanocoating have unique UV shielding properties. Furthermore, it was observed by SEM and AFM that the rough surface morphology of the nanocoating was the main reason for the decrease in the gloss of WPU-g-HM compared with WPU. The thermal conductivity of WPU-g-HM was 0.0347 W/(K·m), and the water contact angle was 100.3°, which indicated that the multifunctional WPU composite coating was successfully prepared.