“Glass transition in thermosetting clay-nanocomposite polyurethanes”,

In thiswork nanocomposite in a polyurethane (PU) matrix, using an organically modified montmorillonite (OMM), were studied. An amount of organoclay ranging from 2% up to 6% by volume was added to the polyol component of the resin before mixing with isocyanate. The basal distance ofOMMbefore and after mixing with the polyol and after curingwas characterized by X-ray diffraction. The glass transition temperature (Tg) of PUnanocomposites, measured using differential scanning calorimeter, increases with increasing the volume fraction of OMM. On the other hand, the heat capacity increment, Cp, decreases from that the unfilled PU to that of the sample with 5.7 vol.% of OMM. Therefore the rigid amorphous fraction of the PU nanocomposites increases with increasing volume fraction of OMM. Finally, a three-phase model similar to that applied to study semi-crystalline polymers,was used to analyze the intercalation of the PU chains betweenOMMlamellae. The definition of molecular cooperativity was discussed for these systems and the characteristic length of the cooperative region was determined, using Donth equation.