Effect of NCO/OH ratio and Ce-Zr nanoparticles on the thermo-mechanical properties of hyperbranched polyurethane urea coatings

摘要

The present study describes the effect of NCO/OH ratio and addition of Cerium (Ce)-Zirconium (Zr) mixed oxide nanoparticles on the properties of Hyperbranched Polyurethane Urea (HBPUU) Coatings. Initially a hydroxyl terminated hyperbranched polymer (HTBP) was synthesized through A_3+CB_2 approach. The HTBP and Ce-Zr nanopowder dispersed HTBP, both were reacted with hexamethylene diisocyanate (HDI) separately; at various NCO/OH eq. ratios to get different NCO terminated HBPU and HBPU/Ce-Zr hybrid prepolymers. These prepolymers were used for the preparation of HBPUU and HBPUU/Ce-Zr hybrid coating films through moisture curing. The techniques such as ~1H NMR, ~(13)C NMR, FT-IR, and XRD have been used for structural information while Dynamic mechanical and thermal analyzer (DMTA), Thermogravimetric analysis (TGA) and Universal testing machine (UTM) have been used for evaluation of thermo-mechanical properties. The combined spectroscopic investigations results indicate the formation of HBPUU network with a degree of branching of 76% while FT-IR deconvolution results indicates the formation of more hydrogen bonded structure with increasing NCO/OH ratio. The XRD and FT-IR studies confirm the presence of Ce-Zr mixed nanoparticles in the HBPUU hybrids. As per TGA and DMTA analysis the thermal stability, char residue, storage modulus (E', material stiffness) and glass transition temperature (T_g), increases with increasing NCO/OH ratio and Ce-Zr nanoparticle loading in HBPUU coatings. In general, UTM data suggest that the tensile strength increases and per cent elongation at break decreases with increasing the NCO/OH ratio and addition level of nanoparticles in HBPUU coatings.