Optical and Mechanical Properties of Cool Roof Paint Containing Hollow Thermoplastic Microspheres

Sammanfattning: This master thesis examines the effect of hollow thermoplastic microspheres in coolroof paints. These types of paints are characterized by their high reflectivity forwavelengths up to 2.5 micrometers and high absorptivity in the IR region. Thethermoplastic microspheres were produced by Expancel®, a unit withinAkzoNobel®. Optical properties were measured using a UV-VIS-NIRspectrophotometer and FTIR. The paint systems were kept as simple as possible, onlycontaining binder, pigment and additive, thus limiting the study to relativecomparisons. TiO2 was used as standard pigment. The additive component was variedbetween thermoplastic, glass or ceramic microspheres. The reference sample usedCaCO3 as additive. The microsphere particle size was found to have the greatestimpact on the paints reflectivity. The smallest microsphere tested in this study, with adiameter of around 10 micrometers was also the best performing. Absorptance andemittance were not found to be affected by incorporating microspheres into thepaint. Thermoplastic microspheres that where coated with TiO2, called coexpandedmicrospheres were also tested. The incorporation of coexpanded microspheresshowed no increase in reflectivity compared to other paints containing thermoplasticmicrospheres. Four different paint systems were color matched (blue) at a local paintshop in order to examine non-white paints as well. Paints containing thermoplasticmicrospheres performed better than paints using any of the other additives,regardless if the paints where white or non-white.