Aromatic polyurethanes: the effect of hard segment and chain structure on their properties

Structural variation and its effect on the properties of aromatic polyurethanes (PUs) with different chain structures have been reported. Polarized optical microscopic studies of aromatic PUs demonstrate the development of micro clusters with increasing hard segment content (HSC). Higher crystallinity has also been proven from differential scanning calorimeter (DSC) and X-ray diffraction (XRD) studies. A globular pattern has been observed through atomic force microscopy (AFM) and the pattern depends on the type of diisocyanate used to prepare the PU. The difference in surface morphology is evident for two different PUs. The tensile modulus increases systematically with increasing HSC while toughness decreases, due to the presence of bigger crystallites in higher HSC polymer. Both the modulus and toughness vary on the type of diisocyanate present in PUs.