Effect of the polymer-filler interaction on the thermo-mechanical response of polyurethane-clay nanocomposites from blocked prepolymer

Thin transparent films of polyurethane-clay nanocomposites were prepared by dispersing different amounts of commercial organo-modified clay in a mixture of cycloaliphatic amines used as chain extender of a blocking prepolymer, in order to investigate the role of the filler content on the thermo-mechanical behavior of the resulting composites. X-ray diffraction measurements evidenced the formation of an intercalated structure, regardless to the clay loading. Furthermore, the optical clarity of the samples was not substantially compromised by the nanofiller addition even at elevated clay amounts. Interestingly, the relatively strong polymer-filler interaction led to a substantial reduction of the matrix crosslinking degree for high clay loadings. Consequently, the relative thermal lifetime was positively affected by the presence of clay up to a filler content of 7 wt%, while uniaxial tensile tests under quasi-static and impact conditions evidenced an increase of the elastic modulus proportional to the clay concentration, without impairing the original tensile properties at break.