Synthesis and characterization of hyperbranched polyester-urethane-urea/K10-clay hybrid coatings

A series of hyperbranched polyester-urethane-urea/K10-clay hybrid coatings (AHBPE-1 and AHBPE-2) have been prepared. Initially, the polyester polyols are synthesized separately in a step-wise manner using pentaerythritol (PE), phtallic anhydride (PTA) and trimethylol propane (TMP). The cetyltrimethylammonium bromide (CTAB) modified K10-clay is used as an organoclay for the hybrid composites preparation and dispersed into the polyester matrix by ultrasonication method. This clay-dispersed polyols are used for further synthesis. The degree of branching (DB), percentage of condensation reaction and quantity of dendritic (D), terminal (T) and linear (L) units present in the polyester are calculated, from the NMR peak integration value. The NMR result suggests that, there is formation of nearly 63% of condensation product in the polyester. A structure-property correlation is established, based on the hydrogen bonding effect with increasing clay content by using the FT-IR peak deconvulation technique. The dynamic mechanical and thermal analysis (DMTA) as well as thermo gravimetric analysis (TGA) results show, an increase in room temperature storage modulus (E′), glass transition temperature (T_g) and thermal stability of the hybrid coatings with increasing clay content and NCO/OH ratio. The contact angle measurement study suggests that, the hydrophilicity of the hybrid films increases with increasing clay content and decreases with increasing NCO/OH ratio.