• Polyurethanes
• nanoparticles
• Ionomer
• Energy saving
• ATO
• PVB

Nowadays energy conservation is an important factor that could be reached in house and building. Nanocomposite coating for windows with solar shield and heat insulator properties could represent an example.
In this work, nanocomposite materials are prepared and investigated starting from two different types of polymer matrices and antimony-doped tin oxide nanoparticles, known for their infrared light insulating properties. The aim is to obtain heat insulator coating for windows by using different preparative approaches. A polyurethanes of synthesis and a commercial polymer commonly used in laminate glass, named as poly(vinyl butyral), are used as polymer matrices.
These materials should be transparent in visible light, able to block near infrared radiation and easy to be applied on glass in form of coating.
Different kind of antimony-doped tin oxide nanoparticles are used: a commercial ethanol dispersion and three ethanol dispersions prepared in our lab from nanoparticles in powder form. Dispersions from powder are achieved with and without the use of a dispersant agent. A dispersant agent able to react with polyurethane is also used in order to covalently link polymer and nanoparticles.
Polyurethane matrices are based on linear thermoplastic polyurethanes formed by hard (aromatic diisocyanate) and soft segments (poly tetramethylene oxide). They are synthesized via prepolymer method followed by a chain extender step, thus leading to a hard-soft segmented polyurethane. Three nonionic polyurethanes are obtained in this way with different hard-soft content and different chain extender. Anionic and cationic derivatives are obtained by post modification of nonionic polyurethanes. In particular, cationic derivatives are synthesized via a quaternization of nitrogen atoms of the chain extender, while anionic derivatives are synthesized through ionization reaction of carboxylic groups of a different chain extender. A cationic polyurethane is synthesized directly, using a chain extender of cationic nature.
Ionic charge on polyurethanes is exploited to create water polymeric dispersion, in order to avoid the use of organic solvent in the final application as coating.
Nonionic polyurethanes and water polymer dispersions are then modified with antimony-doped tin oxide nanoparticles.
Thus, polyurethane nanocomposites are synthesized at different hard/soft content ratio, different % and type of ionic content. Materials are then characterized by several experimental techniques in order to evaluate how the different composition of polymeric matrices can affect morphology, thermal, and spectral properties of polymers and nanocomposites.
Poly (vinyl butyral) is commercially available and it has used without modification. Poly(vinyl butyral) nanocomposites are obtained in three different ways, in order to find an approach that can be scaled up:
• Casting a polymer solution added with nanoparticles dispersed in a common solvent;
• Mixing poly(vinyl butyral) and antimony-doped tin oxide, all in solid state, with a mechanical mixer at high temperature;
• Spray deposition of a metal oxide suspension onto poly(vinyl butyral) commercial film, followed by glass lamination.
All composites both polyurethane and poly(vinyl butyral) are spectroscopically characterized in the 200 – 3000 nm spectrum region to verify the near infrared shielding effect. In order to give quantitative information about efficiency of these materials, parameters of ultraviolet, visible and solar transmittance are calculated.
Size, content and type of antimony-doped tin oxide have influence on infrared transmission, but also visible transmission is affected. Promising results in shielding near infrared radiation while the visible region is maintained are reached at low nanoparticles content. Best results are obtained with laminated glass, which are compared to a commercial energy saving glass.
A study of dielectric spectroscopy, 1H Low-Field nuclear magnetic resonance, Fast Field-Cycling relaxometry and solid state nuclear magnetic resonance on poly(vinyl butyral) and its composites is performed to characterize their structural and dynamic microscopic properties. Composites containing both uncoated and surface-modified nanoparticles are investigated at 5 wt% loading level across the polymer glass transition temperature.