THERMAL AND MECHANICAL-PROPERTIES OF POLYURETHANES DERIVED FROM MONOSACCHARIDE AND DISACCHARIDE

Thermal and mechanical properties of polyurethane (PU) sheets prepared from the glucose/fructose/sucrose-polyethylene glycol (PEG)-diphenylm ethane diisocyanate (MDI) system were examined by differential scannin g calorimetry, thermogravimetry, dynamic mechanical analysis and tensi le tests. The saccharide content was varied at a constant NCO:OH ratio of 1.0. The glass transition temperature (T-g) increased with increas ing saccharide content. The incorporation of saccharides into the PU s tructure results in a higher crosslinking density and a higher content of hard segments. The thermal decomposition was dependent on the sacc haride content, an increase leading to a lower thermal decomposition t emperature (T-d). The dissociation of saccharide OH groups and NCO gro ups is a major part of the thermal decomposition of these PUs. Dynamic mechanical analysis revealed two kinds of relaxation: the high temper ature relaxation corresponds to main chain motion and the other is a l ocal mode relaxation due to non-reacted isocyanate groups. The tensile stress and Young's modulus increased with the saccharide content.