Oligomeric silsesquioxane reinforced polyurethane with enhanced coating performance

A hydroxyl functional acrylic polyol (AP) resin was modified with silicone resin (silanol functional oligomeric silsesquioxane) by simple physical blending and also by chemical reaction between the two with the help of titanate catalyst. The blended (b-APS) and reacted (r-APS) pre-polymers were characterized by Fourier transform infrared (FTIR) spectroscopy, carbon nuclear magnetic resonance (¹³C-NMR) spectroscopy and gel permeation chromatography (GPC). The pre-polymers were then cured with isocyanate to obtain polyurethanes (PU) and their thermal, mechanical and coating properties were characterized. The higher glass transition temperature and storage modulus from dynamic mechanical analysis (DMA) indicates the superior mechanical properties of “silsesquioxane-modified” PU over the conventional unmodified PU. When compared, the PU from r-APS showed better thermomechanical properties than that from b-APS. The former also exhibited reduced phase heterogeneity as visualized by atomic force microscope (AFM) studies. When used as coating materials the incorporation of the silicone component both by physical blending and chemical reaction leads to molecular reinforcement of PU. Remarkable improvement was noticed in the performance properties of the coatings with respect to hardness, tensile strength, heat resistance, gloss and distinctness of image.