Synthesis and properties of polyurethane/clay nanocomposite by clay modified with polymeric methane diisocyanate

A polyurethane (PU)/clay nanocomposite was synthesized from polyol, polymeric 4,4'-diphenyl methane diisocyanate (PMDI), and modified clay with PMDI. To achieve the modified clay with PMDI, the silanol group of the clay and the NCO group of the PMDI were reacted for 24 h at 50 degrees C to form urethane linkage. Fourier transform IR analysis of the clay modified with the PMDI demonstrated that the NCO characteristic peak was observed in the clay after a modification reaction with PMDI. The results of the X-ray pattern suggested that the clay layers were exfoliated from the PU/clay nanocomposite. From the results of the mechanical properties, the maximum values of the flexural and tensile strength were observed when 3 wt % clay based on PMDI was added into the PU/clay nanocomposites. The glass-transition temperature and change in the heat capacity at glass transition temperature (Delta C-p) of the PU/clay nanocomposite decreased with an increase in the modified clay content. We suggested that the decrease in the Delta C-p with the modified clay content might be due to the increase of steric hindrance by the exfoliated clay layers. (c) 2006 Wiley Periodicals, Inc.