Effect of Modified Hollow Glass Microspheres on the Properties of Waterborne Polyurethane Coating

With the increasing demand for deep-sea exploration and underwater operations, the development of high-performance submersible fabrics has emerged as a critical focus within the field of functional textiles. In this study, the silane coupling agent KH550 was employed to modify the surface of hollow glass microspheres (HGM). A composite coating with waterproof and thermal insulation properties was fabricated on nylon fabric by laminating a waterborne polyurethane (WPU) matrix incorporating hollow glass microspheres (HGM) as thermally insulating fillers. The effects of surface modification of the HGM on properties of the composite coating were investigated. The results demonstrate that modification increased the thermal conductivity of the composite coating from 0.052 W/(m·K) to 0.065 W/(m·K) at a filler content of 20 wt%. This increase arises from strengthened interfacial adhesion between modified HGM and the WPU matrix, which reduces porosity within the coating. The water contact angle of the composite coating increased after modification, reaching 112.9° when the filler content was 20 wt%, which is 15.6° higher than that of the unmodified counterpart. This can be attributed to hydrophobic amino groups on the modified HGM surface and the formation of micro-nano rough structures. The flexibility of the composite coating was significantly enhanced after modification. The elongation at break reached 303% when the filler content was 20 wt%, which is 191.35% higher than that of the unmodified counterpart. This indicates that the interface optimization effectively delays the onset of brittle fracture. This approach not only expands the application of HGM as a thermal insulation filler, but also contributes significantly to improving diving suit materials.