Urea-urethane elastomers were synthesized in a polyaddition reaction of ethylene oligo­adipate (OAE) of an average molecular weight 2000 a.u. with MDI diisocyanate. Their micro­structure and properties were studied. Dicyandiamide was used as a chain extender. In order to obtain hybrid nanocomposi­tes, OAE was modified by the reaction with methylalumoxanes (MAO) prior to use. The excess of active methyl groups of MAO was deactivated by the reactions with water, alcohols or alkylphosphates. This method allowed to introduce nano-sized aluminum-oxide based moieties into the polyurethane. The amount of nanoparticles varied from 2 to 5 % by weight. The mixture of substrates was cast into special moulds and curing process was then carried out at elevated temperature. The aim of the study was the homogeneous molecular dispersion of aluminum-oxide units in order to obtain urea-urethane nanocomposites with higher fire-resistance and improved mechanical properties. Microstructure of the nanocomposites was studied with the HRSEM. Mechanical properties were examined by standard testing procedures. The parameters meas­ured were: tensile at 100% and 300% elongation, tensile strength, elastic modulus, tear strength, elongation at break, permanent set, hardness, abrasive wear. Fire-tests were also made using Cone calorimeter.

The results of the microstructure studies show uniform incorporation of the nano-sized aluminum-oxide units in the polyurethane bulk. Such properties as Young's modulus, hardness and tensile at 100% elongation increased. A significant decrease in the heat release rate was also observed.

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