Hollow Thermoplastic Microspheres in Elastomeric Cool Roof

By Jan Nordin, Olof Sandin, Peter Greenwood

Hollow ultra-low density thermoplastic microspheres can be used as filler in elastic waterproof/cool roof coatings to improve a number of important properties of the coatings. Micron sized hollow microspheres have a surprisingly strong effect on reflecting solar radiation and reducing the temperature of cool roof coatings. Results from solar reflectance measurements show that the coating system filled with hollow microspheres reflects solar radiation of all incoming wavelengths.

Hollow microspheres can be combined with reflecting pigments, making it possible to formulate coatings with extremely high values for total solar reflectance (TSR). Dirt pick-up resistence (DPUR) is not significantly affected by the choice of filler for the formulations evaluated here. This article presents convincing results that DPUR can be drastically improved by adding surface modified silica nanoparticles to the formulations.

The silica nanoparticles tend to migrate to the coating surface and affect both the surface energy and the tackiness of the surface. Adhesion to steel surfaces is significantly improved by exchanging the inorganic filler for thermoplastic hollow microspheres. This effect is true for both wet and dried coatings and will help improve the water-proofing properties of the coating. It is likely that the thermoplastic properties of the hollow fillers count for part of this effect.