Organically modified montmorillonite hyperbranched polyurethane-urea hybrid composites

The synthesis and characterization of hyperbranched polyurethane/clay (HBPu/o-clay) hybrid coatings prepared from HB aliphatic polyester polvols (HPs) and isophorone diisocyanate (IPDI) is reported. The HPs are prepared by reacting adipic acid (AA) separately with pentaerythritol (PE). trimethylol propane (TMP) and glycerol (Gly) in different mole ratios of 0.6:1.0, 0.8:1.0 and 1.0: 1.0, respectively. K+-montmorillonite (K10) modified with cetyltrimethyl ammonium bromide (CTAB) is used to increase the compatibility between the clay and polymer matrix. The clay is well-dispersed into the polyester matrix by ultrasonication method. Later on, NCO capped HBPU prepolymer (NCO-HBPu) is synthesized from the clay-dispersed polyester by reacting with IPDI at NCO/OH ratio of 1.6:1.0. In the next step, excess NCO content in the binder is cured with moisture. The properties of different HBPu/o-clay hybrid coatings were studied by FTIR, TGA and DMTA instruments and a structure to property correlation is drawn. The deconvolution technique is used to identify the amount of hydrogen bonding present in the hybrid coatings. The TGA and DMTA result showed an enhancement of the thermal stability, room temperature modulus (E') and glass transition value (T-g) for the clay modified hybrid coatings. and increases with increasing clay content. TGA results also suggest that the PE-based HBPu/o-clay hybrid coatings have higher thermal stability than TMP or Gly-based systems, which are in close agreement to the FTIR analysis. (c) 2007 Elsevier B.V. All rights reserved.